Posts Tagged ‘AR-15 lower’
by B.B. Pelletier
Today’s test is shooting the Crosman MAR177 at 25 yards, both with and without the magazine. We’ll also shoot it with the best wadcutter target pellets and the best domed pellets to see what differences there are.
Rather than shoot the rifle myself, I let Mac shoot it this time. He is the better rifle shot between us, and I just wanted to see what the rifle would be like in his hands. He shot it off a bag rest at 25 yards indoors. Ten pellets were shot from the magazine, then another 10 of the same pellet were shot using the single-shot tray. Mac tested both domed and wadcutter pellets, so we get to compare the relative accuracy of both today. And the results did not turn out as I expected.
I’d noted in an earlier report that the particular 10-shot magazine I’ve been using has two chambers with tight entrances. Mac found the same thing without being prompted by me. I had him use the same magazine as I did so I could compare his results with all other variables remaining the same.
You’ll recall that I mentioned not liking magazine guns because of how they handle the pellets. So, today was also a test between the magazine and loading each pellet as you shoot. I’m not saying that all pellets have feeding problems, but that some magazines may have a problem. But when you load each pellet singly, you have less chance of damaging the pellet.
That said, the MAR177 has a gap at the front of the single-load tray that can catch the nose of certain pellets and make it very difficult to load. The H&N Field Target pellets that were the most accurate in an earlier test had this problem and had to be exchanged for a different domed pellet. The H&Ns have a semi-wadcutter rim around the head that just catches in the gap on the tray and causes the pellets to flip up and possibly get damaged on loading. I substituted 7.3-grain Air Arms Falcon pellets that fed perfectly through the tray.
On to the shooting
Let’s get right to today’s test. First, Mac tested the domed pellets at 25 yards.
Mac tried the H&N Field Target pellets first, and they were very accurate, but a couple of them refused to feed through the magazine. But the Falcon pellets fed flawlessly, so we changed the test to use them as the domed pellet of choice. Once again, I want to say that in another magazine this pellet might have fed better, but this is a quirk you get with mags that you don’t get when loading singly.
Clearly the single-loaded pellets are more accurate than those loaded by the magazine. That may not hold from magazine to magazine; but for this one mag, you’re better off loading the pellets one at a time. Let’s see how the rifle does with wadcutters at 25 yards.
The trend continued with the wadcutter pellets. The R10s grouped even tighter than the Falcons at 25 yards, and those that were loaded singly did much better than those that fed through the magazine.
What have we learned?
First, we’ve learned that some magazines do influence the accuracy of the gun with all ammunition — or at least with the pellet types used in this test. A different magazine might well give different results, but one thing it will never do is outshoot loading the pellets by hand, one at a time. As a 10-meter shooter, I knew this going into the test. But it was nice that we were able to demonstrate it so clearly.
Next, we see that wadcutters were more accurate than the domes in this test. Even though both pellets were very accurate, the wadcutters had the edge. That was the part that surprised me. I’d expected the domes to take over at 25 yards.
The bottom line
The Crosman MAR177 is a valuable addition to an AR and a wonderful target rifle in its own right. It was held back in this test by the use of an AR National Match trigger, which is by no means as good as a target trigger on an air rifle. Even so, we see accuracy that any 10-meter precision rifle would be proud of.
I think Crosman has made a winning rifle in the MAR177. And when they bring out more powerful versions of it in the future, it’ll be all the greater justification for owning an AR! My thanks to Crosman for the loan of this MAR177 for both this test and for the feature article I am writing for Shotgun News!
by B.B. Pelletier
Today, we’ll look at the Crosman MAR177 upper shooting domed pellets at 25 yards. I’ll be using the 10-shot magazine, so we’ll get to see that in action, as well. I’ll tell you right now that today was a learning day that spawned another report that’s still to come. Read on to learn what it is.
As you know, the Crosman upper receiver is attached to a lower receiver that I built on a Rock River Arms lower receiver shell. I used Rock River parts, and the trigger is an upgraded two-stage National Match trigger, also from Rock River.
To the uninitiated, the term National Match sounds like the finest possible precision. Well, it isn’t! A National Match trigger in an AR is about like a John Deere tractor — strong and effective, but as far from real precision as it is possible to get and still have a good trigger. My trigger has a light first stage and a crisp release in stage two, but it’s not what any target shooter would call precision. The break point is right at 5 lbs. My Trapdoor Springfield, which was made in 1875, has a trigger just as nice. My 1879 Argentine rolling block’s trigger is lighter and crisper, now that I have replaced the heavy service-grade trigger return spring. So understand that National Match does not mean the same as precision. You owners of Rekord triggers don’t know how good you have it.
The National Match AR trigger is quite a bit better than the single-stage trigger that comes standard on a military or civilian AR, but it isn’t a target trigger by any stretch. I tell you that so you’ll understand what I had to deal with in this test.
The MAR’s magazine is the same one that a .177 Benjamin Marauder uses. It’s wound under spring tension as it’s loaded and advances by spring power as the bolt is worked for each shot. Remember that on the MAR, the bolt is retracted by pulling back on the charging handle — the same as all other ARs.
The 10-shot magazine comes from the Benjamin Marauder and is completely reliable, as well as quick and easy to load. Here the last shot is in the magazine, holding it in place. The clear plastic cover is rotated to drop in the other 9 pellets.
The mag loads easy once you know the right procedure. A couple of the chambers were tight, so I used a mechanical pencil to push in the pellets. Once they cleared the lips of the tight chambers, they dropped into place easily. There were no feeding problems throughout the test, which entailed about 90 pellets, give or take.
I mounted a Leapers 4×32 mini scope on the rifle. It’s not a scope that Pyramyd Air stocks, but it would be similar to this Leapers scope. You may criticize my choice for some lack of aiming precision; but when you see how good the little scope looks on the rifle, I think you’ll understand why I went with it. It allowed me to use medium scope rings and still clear the magazine that stands proud of the receiver top. If I were hunting feral hogs with a 300 AAC Blackout or a .50 Beowulf cartridge, this is the scope I would use. No, it doesn’t magnify as much as a good 3-9x scope, so we may have to take that into consideration when we look at these groups.
I sighted-in at 12 feet, using my 10-minute sight-in procedure. If you haven’t tried this yet, you need to. It took just three rounds to get on target; and although a bit of luck was involved, this sight-in procedure always cuts time from the front-end of my scope tests.
Air Arms Falcon
I used the 7.3-grain Air Arms Falcon pellet to sight in. The scope seemed right on for elevation, but off to the right. I dialed in some left correction and shot again. Almost there, but not quite. One more adjustment put me at 6 o’clock, as far below the aim point as the center of the scope was above the bore axis (approximately). I knew I was safe to back up to 25 yards and start shooting.
The next 7 shots made a group measuring 0.422 inches between the centers of the holes farthest apart. It was an auspicious beginning for the test!
It was also the best group I shot with the Falcons. The other two opened up to over three-quarters on an inch, so although they made a good first impression, Falcons were not the best domed pellet in the rifle I’m testing.
JSB Exact 8.4-grains
I also tried JSB Exact 8.4-grain domes. They put 9 pellets into 0.495 inches, but threw the tenth shot low and right, opening the group to 1.047 inches. I detected no reason for this wild shot, so I’ll have to chalk it up to the pellets — maybe.
Next I tried some BSA Wolverines. This is yet another JSB dome that sometimes out-performs anything else. But in the MAR, they were just satisfactory, putting 10 into 0.642 inches.
JSB Exact RS
Another tantalizing group was made by JSB Exact RS pellets. We’ve learned over many tests that the RS is one of the best pellets for low- to medium-powered springers, and the MAR177 shoots at the same velocity, so I wondered how well it would do. Nine shots went into 0.474 inches, but the tenth shot opened that to 0.874 inches. It was a second instance in which 9 shots were tight and the tenth was a flier. I cannot say where in the string the wild shots occurred, though, because the scope couldn’t see the pellet holes as they were made.
H&N Field Target
Next, I tried H&N Field Target domes. A reader recently asked me why I don’t try these, as he had good success with them. I responded that I had, and had not experienced the same success; but when I checked my pellets, I discovered that I’d been shooting H&N Field Target Trophy pellets. The Field Target pellet tin was unopened. See what confusion a small name change can make?
These 8.5-grain domes gave me the best 10-shot group of the test — a stunning 0.441 inches between centers! This is a pellet I will work into future tests, you can be sure. This also serves to demonstrate that although the scope only magnifies four times, that’s good enough.
I was starting to tire from all the concentration, so this was the place to stop. I would say that the MAR177 made a good showing, but also raised some questions.
What comes next?
The performance of the rifle in this test was so intriguing that I want to reshoot the same test, only using the single-shot tray next time. Then I will know for sure whether or not the magazine has any influence over the group size. I’ve always had reservations about magazines in any rifle, and I really want to see if there’s any discernible difference. If there is, I may have to do a lengthy test of magazines vs single-shot operations in PCPs.
The next test that will also offer an opportunity to pit wadcutter target pellets against the best domes at 25 yards. I’ve always maintained that 25 yards is about the maximum distance at which wadcutter pellets are accurate, and we even shot a segment on the American Airgunner TV show in which we put that to the test. The domes were clearly superior to wadcutters at 35 yards, so this test will be at a closer distance and indoors. It should prove interesting.
by B.B. Pelletier
Today is the first accuracy test day for the Crosman MAR177 upper, so let’s see how this baby shoots. Blog reader Darth Cossack pointed out that I had mounted the front sight backwards in the last report, so I fixed that for today’s photo. It wouldn’t have mattered from a shooting standpoint, but we do want the gun to look right.
On this AR-15, both the front sight and the rear sight adjust for elevation, while the rear sight also adjusts for windage. The front sight requires a sight adjustment tool that I don’t have and didn’t see packed with the upper. You can also use the point of a 5.56mm military round, which I have an abundance of, but doing it that way is very laborious. I’m hoping the rear sight adjustments will take care of everything that’s needed.
And one more time for those who didn’t read it — the MAR177 is purpose-built for the new sport of National Match Air Rifle (NMAR). NMAR can be shot with traditional 10-meter rifles (using the CMP classifications of Precision and Sporter) and the course is three positions — standing, kneeling and prone. You can continue to use your shooting glove, sling and shooting jacket for this sport, as well. Shooting trousers are not permitted.
The benefit of the AR-15 type rifle that the MAR177 is a part of is that it helps shooters transition over to National Match highpower shooting, because the lower that includes the trigger can be the same for both rifles. And from a competitive standpoint, the MAR177 is very affordable. The only other AR-type air rifle that’s suitable for this sport is made by Anschütz and sells for $1,850.
It cost me $450 to build my lower receiver, and half of that was the National Match trigger. If I wanted to build a lower on a budget, I could do it for under $200 by careful shopping. And I just saw a complete lower advertised in a local sale for $250. But the trigger would then be single-stage and heavier, though there are ways to gunsmith the pull weight down to the legal range of 4.5-5.0 lbs. And when I say the legal range, I refer to high-power competition, only. An air rifle has no trigger-pull limit, because Precision-class target rifles, which are the Olympic target air rifles, are permitted to compete in NMAR.
Why did Crosman make the MAR177 upper for a firearm lower?
This question is being asked by many airgunners. Why would Crosman knowingly make their upper to fit a lower that then classifies the whole rifle as a firearm under federal law? The answer lies in the tens of millions of AR rifles now in the hands of shooters and the extreme popularity of the model. Crosman is building for a market that is more than a hundred times larger than the current active airgun market in the U.S. Even if only a few percent of those owners decide to buy a MAR177, they represent more than all the active airgunners in the United States at this time.
But Crosman isn’t blind to the potential for sales of an MAR that’s not classified as a firearm. I have no doubt they’re working hard on a lower that will accept a modified MAR upper that will not be classified as a firearm. But these things take time. I would expect such a project to be on the fast track right now, but how long it might take before we see it is unclear.
The difficulties are enormous!
You probably think the MAR was easy to develop. After all — every AR is the same (they’re all held to certain specs), so don’t they just have to develop a gun for one lower that will automatically work on all the rest? Actually, no. When your upper has to interface with all the lowers on the market and all possible combinations of triggers in those lowers, there are bound to be some problems. Crosman did their due diligence in designing a universal upper, but there are bound to be some combinations of lower receivers and triggers that experience temporary problems. That would be true for any company designing any new AR-15 upper from scratch.
As I mentioned in Part 2, my Rock River lower and National Match trigger worked fine from the first moment I assembled the rifle, so every new owner can expect success, but there are bound to be some hiccups. There are synthetic lower receivers on the market that are being sold on a price basis that are known to have interchangeability issues with firearm uppers, and this is going to carry over to the MAR177 as well.
I’m not going to list those brands here, but if you do a search for AR-15 lower receiver problems, you’ll come up with a good list of what to avoid. The problems are both the lower receivers, themselves, and the separate parts kits to complete them. People are buying these receivers and parts based on price, alone, and they’re running into problems when one brand of lower won’t accept another company’s parts kit and then work with those three other uppers.
Somebody asked me why I chose a Rock River lower receiver and a Rock River parts kit, and I’m telling you why. There are other brands that are just as good, and a few that are even perhaps better, such as the Giessele National Match trigger that one of our readers mentioned, but you have to be aware of the fact that not all AR-15 uppers fit all AR-15 lowers.
What I’m testing
One final comment I want to make. Building a gun like this is full of decisions. You are free to choose whatever appeals to you; but once you choose, your path is determined by the decisions you make. As I said before, there’s no trigger-pull weight restriction in the NMAR class for air rifle shooting, but if I were to want to use the same lower in a match with a firearm, I would be restricted to a weight range for the trigger release and also the style of pistol grip. While I’ll probably never compete in a high-power military-style match, I wanted to shoot a gun that would qualify. It was a choice I made, and one that you do not have to follow. But that choice led me to a certain level of performance in the rifle I am now about to test.
I’m also shooting the military-style post front sight. An aperture front would allow more aiming precision; but if you want to use the MAR as a training tool for your high-power competition rifle, you’ll stick with the sights that come on the upper.
I shot 5 shots per group off a rest at 10 meters with each pellet I tested. Since there’s going to be more testing with this gun, I didn’t try to test all the pellets I have, but I did try eight different ones.
Sighting in was done with the Crosman Premier Super Match target pellets that Crosman packed with my test gun. And they were astonishingly good! The group fired for record measured 0.144 inches between centers. That’s in the range for CMP (Civilian Marksmanship Program) and NRA Sporter class 10-meter rifles that have much lighter triggers and aperture front sights. I was impressed.
Loading is not perfect
I used the single-shot tray for all this testing. This is the same tray that the Benjamin Marauder uses, and there’s a small gap just before the breech of the barrel. If you try to load the pellet tentatively, the head drops into the gap and binds. If you slam the bolt home too fast, the pellet jumps up in front and also jams. It takes a while to get the right closing speed so the pellet feeds smoothly. Not all pellets jam this way, but a couple are particularly bad. You’ll have to try it for yourself if you use the tray. I was able to get the feed right for every pellet I shot, so it’s not a problem — you just have to spend some time to learn the peculiarities of the gun with the ammo you choose.
The second-best pellet in the test was the Gamo Match. While the group they made looks large, it’s so round that it doesn’t take up that much room. In reality, this probably means they’re not really second best, but I may have made a small aiming error with one of the other pellets. However, it’s surprising that such an inexpensive pellet is also this capable.
RWS R10 7.7-grain pellets that are no longer available gave the best results, with a group size of just 0.106 inches between centers. I shot them early in the test and was probably more rested than I was later, so my eyes were working at their best.
The other pellets
Besides these three, I tried five other target pellets. They were all very equal to the Crosman Super Match, and the largest group fired during the test was 0.162 inches with RWS Hobbys.
JSB S100 Match
One test like this is not enough to determine the most accurate pellet. If I were to do the same test again, the results would no doubt change. Lots more testing is needed to find that one best pellet for this competition air rifle. However, one test was sufficient to prove that the MAR177 has everything going for it. It’s accurate, easy to use and conserves air like a free diver. It mates to an AR lower perfectly to become the best possible training system for AR shooters.
I have more plans for this rifle. Next, I plan to mount a scope and test the rifle with accurate domed pellets at 25 yards. I believe the MAR177 has more to show us.
by B.B. Pelletier
Today, we’re going to see how the new Crosman MAR177 upper performs! Because this rifle is a precharged pneumatic, I used my Shooting Chrony Alpha chronograph to analyze the power curve. Though not absolutely necessary, a chronograph can eliminate a lot of shooting time and let you know how the rifle shoots on the first session.
The test rifle was showing a charge of just less than 1,800 psi when I started the velocity test. I chronographed Crosman Premier Super Match target pellets that Crosman sent with the upper for testing the rifle.
The first shot went 582 f.p.s., which sounded to me as though it might still be within the power curve. So I fired 16 more shots and the velocity ranged from a low of 559 f.p.s. for the final shot to the 582 f.p.s. that was the first shot. At that point 17 shots had been fired and the pressure gauge was reading 1,600 psi, so I guessed that the gun had fallen off the power curve. The average for these 17 shots was 569 f.p.s.
I filled the reservoir until the gun’s pressure gauge indicated 2,000 psi. I then fired five shots that ranged from a low of 580 f.p.s to a high of 585 f.p.s. It seemed the gun was certainly now on the power curve and that it hadn’t been that far off the curve on the first 17 shots.
But just to be sure, I filled the reservoir to 2,200 psi and fired another five shots. This time, the velocity ranged from a low of 578 f.p.s. to a high of 586 f.p.s. That’s not much different than the reading on the 2,000 psi fill, so the rifle is clearly on the power curve and has been since at least 2,000 psi. But then it wasn’t that far off at 1,600 to 1,800 psi, either.
To see if these assessments were correct, I filled the rifle to 3,000 psi — the top of the white sector on the onboard pressure gauge. If the gauge was calibrated correctly, the rifle should now be at the top of its power curve.
Too much pressure
If you ever needed to see a demonstration of what over-pressurizing a pneumatic gun will do, this is it. The first shot after the fill went out at 549 f.p.s. and the next one went 537. In fact the first 11 shots were all below 550 f.p.s. Shot 12 went out at 551 f.p.s., and the pressure gauge on the gun read 2,900 psi. I accepted that this is the maximum fill pressure for this rifle. More than that shuts the firing valve too fast and costs velocity.
I then fired 33 more shots, for a total of 34 good shots (so far) on the 2,900 psi fill. The lowest velocity was 534 f.p.s. and the highest was 562 f.p.s., for an average of 552 f.p.s. At that velocity with this pellet, the rifle generates 5.39 foot-pounds of muzzle energy.
Having established the top fill pressure, I proceeded to test the rifle’s velocity with other pellets without refilling the gun. I tested only target pellets, but the test was more for the weight of the pellets than for their shape.
RWS R10 Match 7.7 grains
I tried the RWS R10 Match pellet that weighs 7.7 grains. This one is now off the market, and there is no replacement. It is in-between the RWS R10 Match pistol pellet that weighs 7 grains and the RWS R10 Match Heavy pellet that weighs 8.2 grains.
This one averaged 588 f.p.s. for 10 shots with a 13 f.p.s. spread from 581 to 594 f.p.s. That generates an average of 5.91 foot-pounds at the muzzle.
H&N Finale Match Rifle
H&N Finale Match Rifle pellets weigh 8 grains, even, and averaged 575 f.p.s. in the MAR177. The velocity spread went from 571 to 585 f.p.s. This pellet generates an average of 5.87 foot-pounds of muzzle energy.
The final pellet I tried was the 7-grain RWS Hobby. They averaged 609 f.p.s., but the velocity spread was larger than the other two pellets. It ranged from 593 to 625 f.p.s. At the average velocity, this pellet generates 5.77 foot-pounds of muzzle energy.
Back to Premier Super Match
After these three pellets had been tested, there were a total of 64 good shots on this fill. Remember — I’m counting the start of the fill from where it passed 550 f.p.s. for the first time. That was when the gun registered 2,900 psi on its gauge. I shot another 10 Crosman Premier Super Match pellets, and this time they averaged 567 f.p.s. The spread went from 559 to 571 f.p.s. At the average velocity, this pellet generates 5.64 foot-pounds of muzzle energy.
How many shots per fill?
I fired 74 good shots on the first fill, and stopped with 2,200 psi remaining in the reservoir. If I continued to shoot until 1,600 psi, as the testing indicates is possible, that would add another 50 shots, minimum, to the shot count, taking the total to 124 shots on a fill. That’s more than enough, but what I now know is that the gun likes the range of 2,900 down to 1,600 psi on the onboard pressure gauge.
The dynamics of the MAR177
The MAR177 is unregulated, so it relies on just the action of the firing valve to control the velocity of the pellet. In the data I’ve shown here, the lowest velocity for a Premier Super Match pellet that’s still on the power curve is 534 f.p.s. The highest velocity within the curve is 585 f.p.s. I’m getting the high velocity from the string fired on the 2,200 psi fill. So, this rifle has a large velocity spread ranging from 534 to 586 f.p.s. to get those 124 shots that I maintain are in the power curve. That’s 52 f.p.s., and normally we wouldn’t consider a range that large to be good. But this rifle is meant for 10-meter target shooting, and for that reason I doubt we will see any group enlargement due to velocity. However, I’ll conduct a test to see if there’s any vertical stringing, which is what large changes in velocity can cause.
If we were shooting the rifle at 25 yards and farther, then I would recommend using a smaller section of the power curve. It’s apparent that, as the air pressure drops below 2,000 f.p.s., the velocity rises to the highest it’s going to be with a particular pellet.
If the large velocity spread bothers you, you can limit the fill to 2,800 psi, and your slowest shot will be 535 f.p.s. Or limit it to 2,700 psi and the slowest shot will be 549 f.p.s. If you decide to do the latter, your total shot count will be 104 shots, and the total velocity spread will be 37 f.p.s. For my money, the 2,900 psi fill looks best, so that’s what I’m going to use to test this gun.
This discussion would be impossible without the use of a chronograph. You would just load the rifle and shoot until the point of impact started to wander. By using the chronograph, you can look at the performance from shot to shot and also understand that there are always going to be some anomalies in the data.
If a different pellet is used to baseline the rifle, things could change dramatically. Premiers are made from a hardened lead alloy, where the other three pellets are closer to pure soft lead. That will have an effect on the numbers you get.
A major lesson demonstrated
This test demonstrates clearly why you cannot simply act as though the pressure gauge on a PCP is reading correctly, and the valve is responding according to the specifications. I’ve said in the past and I’m saying it again — these small gauges can easily be off by 300 psi yet still be considered accurate. The same is true of the firing valve — it may operate at a slightly different range of air pressures than the spec states. If you want to know for sure, you have to use a chronograph.
What we have seen here is the fact that this gun operates on less peak reservoir pressure and also continues to operate to much lower ending pressure. Without these tests, that information would not be known, because you certainly can’t tell from the sound of the discharge. Instead of obeying the owner’s manual in rigid lockstep, we’ve used a diagnostic to learn how our particular gun performs. Knowing that, we can get the best performance that this individual airgun has to offer.
The muzzle compensator
I mentioned the compensator in an earlier report, but I wanted to show it to you here. You’ll see that the turbulent air gets stripped off and cannot follow the pellet downrange after it leaves the muzzle because of how this compensator is designed.
When the pellet leaves the muzzle, it passes through a separate piece that strips off the turbulent air and directs it to the side. The pellet is free to fly straight without the turbulent gasses acting on its skirt.
by B.B. Pelletier
Today, I’ll document the build of the AR-15 lower receiver that was required for the test of the Crosman MAR177 upper. This was a fascinating and somewhat scary project, because I was venturing into waters that, for me, are uncharted. On one hand, I know that the AR-15 is a popular firearm, so I expected to find all the information I needed to build the lower receiver on the internet. On the other hand, how good that info might be was completely unknown. I was scared because it has been over 30 years since I have had an AR apart, and even then it was only to clean the rifle after firing. I never had to build one.
After seeing my level of expertise with woodworking (the ill-fated Bronco article in which I destroyed the stock to mount a peep sight), you might feel some concern for my abilities as a gunsmith. Fear not. I used to make a nice part-time income from tuning single-action Colts, and I’ve tightened and accurized several M1911A1 pistols with demonstrably good results. Though I’m no craftsman, I can gunsmith metal parts when I need to.
It’s not that hard!
I needn’t have worried. The lower receiver of an AR-15/M16 is a very uncomplicated design and goes together without a lot of trouble. You do have to take some care with certain parts, as the receiver is made of aluminum and will break if handled improperly. Besides that and a couple small springs that fight to escape, there’s really nothing that’s too difficult if you take your time.
Step one was to photograph the parts that Rock River sent for the lower receiver. This soon proved invaluable when one of the smallest parts went missing for several minutes during the assembly. When I got to the place where I needed the part, a wee-teeny pin called a bolt catch buffer, but couldn’t find it, I assumed that Rock River had failed to send it. That infuriated me, because how was I supposed to know I needed one, since this was my first lower to build? This was the greatest fear I had about building this lower receiver.
I searched everywhere, even to the point of getting down on the kitchen floor (yes, I actually did do all the work on the kitchen table), where I found a small black beetle about the same size. He was dead, plus he didn’t have the same internal dimensions as the part I was searching for, so I kept looking. I even called Edith in on the hunt, since she has a better record for finding escaped parts.
After a while, I was certain Rock River had omitted the part from the kit they sent, so I checked the photo I had taken earlier of all the parts, and there it was. I had it when I took the picture, but not now, when I needed it. I then started putting all the parts back into their plastic baggie, thinking the build would be delayed until I got another part. And that’s when the part I needed fell out of another hollow part that was ever-so-slightly larger!
I had found a great website with step-by-step photos of the assembly, so everything was straightforward to a certain point. I was warned that certain small springs would try their best to escape, so I made a cloth-cushioned backstop to catch them when they flew. It was used about five times, so the warnings were well worth heeding. I also swept some small parts off the cloth work surface with the cuffs of my shirt, but fortunately Edith’s better eyes found them right away.
And then things came to a halt. I had ordered the National Match trigger and the internet instructions I was following were for the single-stage standard trigger. The parts I had didn’t match the instructions. Unfortunately, I was unable to locate any specific instructions for installing a Rock River National Match trigger online, and Rock River had only sent instructions for a person swapping a trigger in a lower that was already built up. At this point, I was on my own. Fortunately, this trigger/hammer combination installs on the only two pins that fit through the lower receiver, so it’s hard to mistake where they go. And the National Match trigger incorporates the disconnector — a part that’s separate and installed separately on the standard trigger. That caused me to stop and ponder a few more minutes, wondering if I was missing yet another part. But I used to write manuals for the Army and have seen inconsistencies like this before, so I figured it out after a short breather.
The Rock River Arms National Match hammer (left) and trigger. The instructions failed to note that the disconnector is part of the trigger assembly and doesn’t look like the one for a standard trigger. The hammer spring was also installed backwards, but proved simple to switch once the problem was identified.
Rock River had installed the trigger and hammer springs on those parts when they sent the kit, but unfortunately they got the hammer spring on backwards. So, there was another short delay while I figured that out. In the end, though, everything worked out fine and the lower receiver went together easily.
Once the lower receiver was completed, I installed the A2 buttstock I’d purchased, and that completed the project. The Rock River buttstock is colored medium gray, but they advised that a wipedown with a oily cloth would deepen the color. In time, it will turn to a matching black.
I suppose I spent about three hours doing what might take 30 minutes for someone who’s familiar with the process. The proof of the project was that the trigger and hammer work as they should, and the safety is finctional. And never dry-fire an AR lower without an upper installed, because the hammer will crack the receiver’s walls.
With the lower receiver complete and functioning as it should, it was now the moment of truth. Would the Crosman MAR177 fit properly and function on what I’d just built?
Anyone who has ever learned to clean an M16 or AR-15 knows how the upper fits to the lower. Two captive pins at the front and rear of the lower hold the two assemblies together. When you clean the gun, you typically only remove one of the pins so the lower hinges away from the upper. That gives you access to the bolt carrier and all the parts that require attention. Connecting the lower I’d just built with Crosman’s upper took about 30 seconds. The hammer was already cocked, so I pulled the trigger — and nothing happened!
Once again, I had butterflies in my stomach. Since I’m not that familiar with the AR guns, I wondered what might have gone wrong. Then I remembered my time at the range on Media Day in January, when I first got to shoot the MAR177. It has to be cocked by pulling back on the charging handle! Once I did that the gun functioned as it should! Now, I am ready to test the MAR177.
If you look closely, you’ll see where the MAR177 differs from a regular AR. For starters, there’s an air reservoir underneath the barrel. And the shiny silver thing at the end of the forearm is the side of the built-in pressure gauge. The rifle operates on 3,000 psi pressure and looks easy to fill from a hand pump. As small as the reservoir is, it shouldn’t take too much effort.
The muzzle has an air compensator to strip off the high-pressure air turbulence for better accuracy. What looks like an AR magazine is a solid metal slug for additional weight. The MAR177 comes with a 10-shot magazine (a single-shot tray is optional, but Crosman sent me one to test) taken from the .177 Benjamin Marauder. The carry handle is split at the bottomfor easier loading. The forward assist on the right side of the receiver is just a casting; it does nothing.
The selector switch is attached to the lower receiver, so of course it’s standard. It is right where your thumb expects it to be if you’re right-handed, and after 35 years I had no problem remembering what to do without looking. Of course, an AR-15 is semiautomatic, only, so there are just two positions — Safe and Fire. If you want to rock-and-roll, you have to raise your right hand and swear the oath.
The rifle weighs 9.5 lbs. on the nose when set up as shown. That’s a hair less than a Garand and a touch more than an 03A3 Springfield. Under the rules, a two-stage National Match trigger is allowed to break at between 4.5 and 5 lbs. and here’s how mine went. The first measured shot, which was about the tenth shot since assembly, measured 6 lbs., 9 ozs. As I kept measuring shot after shot, the pull weight kept decreasing until it hit the 5-lb. level. There, it stabilized — and that’s where it’s breaking now. I will lube the sear contact points with some good moly grease and expect the pull weight to drop by a couple more ounces as the rifle gets used more.
The trigger is completely crisp on stage two — as a National Match trigger should be. It works well with the weight of the rifle, and I expect to have more to say about it when I start accuracy testing.
Notice that the pistol grip I chose is a conventional one. You can get all kinds of wonderful grips for your AR, but this is the one you must use in a match — so I went with it.
I’ll try the 10-shot magazine, but right now I have the single-shot tray installed so I can switch from one pellet to another as I learn the gun. The way I shoot airgun matches, I would probably keep the single-shot tray installed, but the magazine could be used, as well, by those who prefer it.
There’s much more to tell you about the MAR177, but I’m going to do that as we progress through the other parts of this report. When I left the Army in 1982, I never thought I would have one of these in my hands again, but Crosman has made the impossible happen.
by B.B. Pelletier
Some announcements before we start:
BSOTW winner Silas McCulfor took this great picture of his sister holding his Beeman Sportsman RS2 model 1073 dual-caliber air rifle.
Get free tickets to the NRA show in St. Louis. If you’re not an NRA member (they get in free) or have family members and friends who aren’t members, Pyramyd air has some free passes for you ($10 value). To get yours, click to send an email request. Limit of 2 tickets per person. Limited supply. First come, first served!
Pyramyd Air is awarding double Bullseye Bucks for each purchase you make from March 15-18, 2012. If you don’t have an account, create one. Then, use that same email address when placing any orders (whether you sign in to your account or not when placing an order). If you already have an account, you’ll get double credit for any orders you place March 15-18…as long as you place them using the same email address as your Bullseye Bucks account (even if you don’t sign in when ordering).
On to today’s blog.
Okay, lads and lassies; settle back while uncle B.B. tells you a nice long story! This report will be a big one because there’s so much to tell.
The Crosman MAR 177 upper is a target precharged pneumatic upper that fits on any standard National Match AR lower (I’ll cover that in a moment) and turns the U.S. M16 service rifle or its civilian-legal semiautomatic counterpart AR-15 into a target air rifle. Those airgunners who own AR rifles can buy the MAR177 right now and have a target PCP that’s ready to go. This report will be a thorough test of that rifle.
But I don’t own an AR-type rifle. And none of my shooting friends do, either. So, I was at a disadvantage when I was asked to report on this unique new air gun.
There have been other air rifles before now that have resembled the AR-15/M16. Crosman just introduced their M4-177 multi-pump rifle that I tested for you at the end of last year, and back in the 1990s they made the much simpler A.I.R. 17 — another multi-pump that was crude but did follow the AR styling. So, the story is not that an AR airgun has been made. The story is that this one is a precision target rifle and should rival some 10-meter rifles.
The AR system
Before I continue, everybody needs to be on the same page. The AR system that the Crosman MAR (modular adaptive rifle) belongs to is comprised of two principal subassemblies — the upper receiver and the lower receiver. The upper receiver contains the barrel, gas system, bolt, sights and operational hardware for the rifle. The Crosman MAR177 is an upper. I will talk a lot about the upper throughout the rest of this report, but let’s look at the lower receiver for a moment.
The lower, as it’s called, is a frame that contains the operational parts, pins and springs for the trigger, selector and safety, magazine catch, as well as the buttstock and buffer assembly. It’s considered by the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATF&E) to be a firearm. It’s the part that has the serial number. You can buy and sell uppers almost anywhere in the U.S. without paperwork, but each lower is classified as a firearm. The fact that this is a modular system with many different uppers — all on one lower — allows you to own many different rifles, all under one registration.
But I didn’t own an AR — so I didn’t have a lower receiver and the MAR177 isn’t sold as a complete rifle, yet. There are plans to build it that way at some time in the future, but for now all you can buy is the upper. I needed to get a lower.
At first, I looked around for just a complete lower receiver to buy used, and they do exist, but as I searched I found that the people who have them don’t always know exactly what they have. For example, the upper and lower attach via two cross pins, and there have been different sizes of pins over the years. Colt made pins that were larger than those made by other manufacturers, so you might get a Colt lower that doesn’t fit the MAR upper. There are bushings to reduce the sizes of the holes in the lower; but since I was doing this from scratch, I didn’t want to begin with a workaround.
I located a brand new Rock River Arms lower receiver that was stripped of all parts. It was just the receiver shell by itself. But there are parts kits to build up such receivers, so I went online and ordered a National Match lower parts kit and an A2 buttstock assembly from Rock River. I would build the receiver myself; and when finished, I would have a complete Rock River lower — not a bad thing to have. Rock River is a good name; one of many you will find if you look. And there are also a few names to avoid — just as there are with airguns.
When I placed the order, though, I failed to notice the fine print at the bottom of the Rock River webpage that said some of the parts were on indefinite backorder. They didn’t specify which parts those were from the hundreds of choices on the page, but sure enough it turned out to be the entire parts kit I needed for this report. That’s because Rock River is currently experiencing a 60-90-day backorder status on their whole rifles, and they certainly aren’t going to sell their parts faster than they can build entire rifles to sell. It makes perfect sense, but only when you know it. And I only found out when I didn’t get the parts I ordered. So, I had a stripped receiver without the parts to complete it.
Once I realized my backorder status, I placed a call to Rock River to see what the expected delivery date would be, and that’s when I learned everything I have just shared with you. I then explained my short publishing deadline to them (a special feature article in the July color issue of Shotgun News) and they bent over backwards to fix the problem — but don’t expect them to do the same for everyone. If you want to build a lower receiver, you had best first pin down a source for parts before doing anything else. So, this test is made possible through the good graces of Rock River Arms, who, before last Wednesday, had never heard of Tom Gaylord.
National Match lower
Now that you know what a lower receiver is, what’s so special about a National Match lower? Simply put, it’s a lower that meets the specifications for the U.S. Service Rifle National Matches held at Camp Perry, Ohio, every year. One of the most important aspects of this specification is the trigger. Standard AR rifles come with single-stage triggers that are barely adequate at their best. But the National Match specification allows for a two-stage trigger that breaks cleanly with no less than 4.5 lbs. of force. There’s a host of additional information available for National Match triggers; but for our discussion, this is sufficient.
I was hardly going to test the MAR177 — a target rifle — with anything less than a good trigger. I say “good” advisedly; because to someone used to a nice match airgun trigger or even a Rekord sporting trigger, these AR triggers are fairly crude — even those that are National Match. But in the sport they’ll be used, the National Match triggers are as good as you’re allowed to have. Testing the new air rifle upper with a stock single-stage trigger would be a crime.
You’ll watch the build
That’s enough about the lower for today. When the parts arrive, I’ll photograph their assembly and describe the experience for you. For now, let’s concentrate on the MAR177 upper from Crosman.
The Modular Adaptive Rifle (MAR) is a .177-caliber target upper that operates on compressed air. It’s a 10-shot repeater with Crosman’s (Benjamin’s) familiar rotary magazine. My test rifle also came with the single-shot tray for loading pellets one at a time. The rifle is not semiautomatic like most ARs. It feeds and cocks via the retraction of the charging handle, so for each shot the handle must be pulled back.
I shot a preproduction version of the rifle at this year’s SHOT Show on Media Day. But standing on an outdoor firearm range with hundreds of firearms being discharged is not the best place to evaluate a target air rifle. And I couldn’t even evaluate the trigger of the rifle I tested, because it will differ from the trigger I put into my gun. Are you getting a sense of how this modular thing works?
The target pellets exit the muzzle at up to 600 f.p.s., putting them in exactly the same range as most modern 10-meter target rifles. The barrel is from Lothar Walther, which leads me to expect accuracy will be the same as Crosman’s Challenger PCP target rifle.
Unlike airsoft ARs and the two muti-pumps mentioned above, this upper is full weight and will feel like a firearm when mounted on a lower. Therefore, besides being a match rifle, the MAR is also ideal for owners of ARs who want to train with their rifles in their homes under safer range conditions and at a fraction of the cost of even reloaded centerfire ammunition. They can shoot a couple thousand rounds for less than $50 when they use Pyramyd Air’s “Buy three, get the fourth tin free” promotion. So, even when the initial purchase price of $600 for the MAR and the cost of a hand pump is factored in, a serious shooter will get his money back in less than a year and will be training ten times as much with his service rifle.
The MAR operates at pressures between 1,000 psi and 2,900 psi (69 bar and 200 bar, respectively). Crosman says you’ll get up to 120 shots per fill. As the reservoir appears to be the same as the one on their Challenger PCP, I would expect that estimate to be correct.
The gun comes with service-style sights. The rear has two peep sizes, accessed by flipping the post they’re mounted on. And the rear sight is adjustable for both windage and elevation. It’s built into a conventional carry handle, like the rear sight on many ARs. The front sight is a plain post that’s also adjustable for elevation via the same type of detent locking mechanism found on other ARs. You can also remove both sights, and there’s a Mil-Std 1913 Picatinny rail underneath, for those who want to mount optical sights.
There’s a lot to this new rifle, so we’ll see more of it in the reports that follow. And the MAR isn’t the only AR-15 PCP pellet rifle on the market. Anschütz also sells an entire rifle with similar features for around $1,850. So, the MAR177 is even bigger news, because it offers all this value at a fraction of the cost. Figure around $500 if you build a lower like I’m doing. If you already own an AR, there’s no additional cost. Either way, this gun is a bargain!