Posts Tagged ‘JSB Match Diabolo Exact Jumbo Monster pellets’
by Tom Gaylord, a.k.a. B.B. Pelletier
Air Arms Shamal is an attractive PCP. It was Air Arms’ first precharged rifle.
This report covers:
• Trigger adjustments.
• Discovering the maximum fill pressure.
• Shot count.
• Velocity with various pellets.
• Discharge noise.
In this report, we’ll discover the Shamal’s pressure curve, which will be instructional for all who are new to precharged airguns. As I mentioned in the first report, this rifle didn’t come with a manual; so when I got it, I had to discover the pressure curve on my own. I did, and it turned out the rifle wanted an initial fill pressure of 2,600 psi. That was on the gauge that was on the fill device that came with the rifle — the device that I no longer have. I need to find out where on the gauge of my carbon fiber tank the needle wants to be when the rifle is full. These small pressure gauges are not that precise, so the number could be off by several hundred psi. Also, the gauge on my carbon fiber tank isn’t marked in hundreds of psi. There will need to be some interpolation involved.
More than a decade has passed since this rifle was mine. I’m not sure where it’s performing today. So in all respects, this is a brand new air rifle to me. That will benefit you if you want to look over my shoulder while I do what needs to be done.
Before I get into that, however, I first want to address the adjustable trigger. Shamals haven’t been around for a long time and there isn’t that much written about them. I want this report to serve as an owner’s manual for all who get one in the future.
The Shamal came with two different triggers — a standard one that my rifle has and an Olympic trigger that sounds more adjustable, but which I know nothing about. My trigger has 4 adjustment screws. From the back to the front (holding the rifle on your shoulder) they are:
1. The sear engagement (clockwise to reduce).
2. The first-stage travel (clockwise to reduce).
3. The first-stage weight (clockwise to increase).
and in front of the trigger:
4. The second-stage weight (clockwise to increase).
Trigger-adjustment screws: (1) Sear engagement, (2) first-stage travel, (3) first-stage weight and (4) second-stage weight.
When I tested the trigger with my electronic gauge, the firs-stage weighs just under 6 oz., and the let-off was between 12 and 14 oz. The first stage is long, which I like, and the release is as light as I like a trigger to be, so I’m satisfied with this trigger as it stands.
Discovering the max fill pressure
This is something that has to be done whenever a new gauge is used. I had data from previous tests that told me the fill pressure should be 2600 psi, so I filled from my carbon fiber tank to 2750 psi. That gave me the following velocities with the same 14.3-grain Crosman Premiers I used over a decade ago.
The fill pressure at the end of this string was 1500 psi. This string tells me almost everything I want to know about this rifle. First, the fill pressure I used was way too high. I’ll fill the gun again to a much lower pressure and see where that gets me.
Next, there are just under 20 good shots on a fill — down from what I thought so many years ago. I like the velocity that runs from 780 to 806 — a spread of 26 f.p.s. Looking at the curve for Premiers, I should start with shot 18, although the shot before that didn’t record, so I can’t be certain whether it was any good or not.
If I end the string at shot 34, I’ll get 17 full-power shots close to my desired range. What should the starting air pressure be? That’s solved easily.
I’ll guess that 2350 psi is the start point. I filled the rifle to that pressure and got the following results.
Okay, as the pressure inside the gun has decreased with each shot, the velocity has increased. The last shot was 781 fps, which is as low as I want the velocity to go on the power curve I’m willing to accept. The gun’s reservoir pressure has now dropped to the maximum pressure that will give me a velocity on my desired power curve (781 fps).
The velocity of 781 is at the bottom of the power curve that I have identified for this rifle. Since my last shot was 781, the rifle is now on the power curve. The pressure in the reservoir is now at the highest it can be and still give me the velocity I want. From this point on, as the rifle’s reservoir pressure drops, the velocity will either increase or remain stable. As long as it’s at 780 fps or higher, the rifle is on the power curve I’m looking for.
Now I can find the ideal starting fill pressure for my desired velocity range. All I have to do is start to fill the airgun, again. When the needle stops moving fast, indicating the fill hose is full and the gun’s intake valve has just opened, I stop the fill by closing the tank’s valve and look at the needle. The needle is pointing at the air pressure that is in the gun’s reservoir. I can see on the gauge that this rifle likes a starting fill pressure of 2250 psi!
To confirm that I’m right, I fired one more shot with Premiers. It went 781 f.p.s. Bingo! I’m right at the start of the power curve, with at least 16 more good shots in the reservoir.
I also discovered that the rifle performs very much the same as it did long ago. I’m using a different chronograph, yet the velocities from the late 1990s and today are within a few f.p.s. of one another.
The power curve I’ve accepted gives me an average velocity of 792 f.p.s., which is good for 19.92 foot-pounds of muzzle energy.
I will now test the velocity of other pellets, but I’m not going to shoot long strings and get the averages. I will shoot 2 of each pellet and take the lowest velocity of each pellet as the average for that pellet. While that’s not exact, it’s far faster than shooting whole strings and averaging. I know I’m on the power band for the next 16 shots; and if I use even fewer than 16 shots (4 pellets x 2 shots each = 8 shots), I can be sure that all of them are on the power band. The power band is the place where the velocity of any pellet will vary the least.
Eun Jin domes
This 28.4-grain Eun Jin dome pellet gave me velocities of 592 and 586 f.p.s. Taking the lower number as the average, I get a muzzle energy of 21.66 foot-pounds.
The Beeman Kodiak pellet weighs 21.14 grains and gave me velocities of 683 and 680 f.p.s. That’s very close to the “magic” velocity of 671, where the weight of the pellet in grains equals the energy in foot-pounds. Using the low figure of 680 f.p.s., this pellet gave an energy of 21.71 foot pounds at the muzzle.
JSB Exact Jumbo Monsters
Next, I tried JSB Exact Jumbo Monsters — a 25.4-grain pellet. They gave me velocities of 584 and 611 f.p.s. Using the lower number, that’s a muzzle energy of 19.24 foot-pounds.
The bottom line is that this Shamal is a 20 foot-pound air rifle as it’s operating now. That’s what it was when I owned it in the 1990s. So, the rifle hasn’t changed, but the gauges have changed and so has my perception of the total number of shots that are available. So, this update was important to the operation.
I don’t know what I was thinking when I reported the Shamal as a quiet air rifle before, but it isn’t. It sounds exactly as loud as a .22-caliber Benjamin Discovery running at the same power.
Someone asked about the loading room at the breech, and on this rifle there’s a generous amount. There’s no loading trough, so it’s easier to get your fingers behind the breech with a pellet. And all pellets load easily because there’s no rifling at the breech. Rifling doesn’t start until after the air transfer port, which is deep inside the breech. The bolt nose has a long probe that pushes the pellet past the air transfer port and into the rear of the rifling.
That’s a 28-grain Eun Jin standing on the receiver. It’s one of the longest .22-caliber pellets around. As you can see, there’s plenty of room at the breech.
That’s it for this look. Next time I’ll scope the rifle and head to the range.
by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s report is a second installment from our blog reader RifledDNA, a.k.a. Stephen Larson. He’s modified his new Benjamin NP Limited Edition and wants to tell us how it’s going.
If you’d like to write a guest post for this blog, please email me.
Over to you, RifledDNA.
Today is part 2 of my new NP Limited Edition, and we’ll look at what’s changed on the .22-caliber rifle since I took it out of the box, what pellets it likes so far and the accuracy I’ve been able to achieve. I wrote an earlier part 2; but the day after it was finished, Crosman alerted me they had a new stock for me. A few days after that, my order of pellets would arrive. It made sense to wait until these things were available for inclusion in this report. Both packages arrived, the stock was installed, the pellets have been tested and I can now tell you everything that has happened in one big mess of journalistic chop suey.
First, let’s see what I’ve changed on the gun. In the first report, I told you how uncomfortable and misconfigured the grip and trigger assembly seemed to me. I’m used to pistol grips, and the Benjamin NPS was designed for one. I knew that a stock with a pistol grip that fit properly must be found.
I approached Crosman and asked for a Benjamin Legacy Jim Shockey stock based on the fact that rifle is similar to my rifle and both have the highly angled forearm screws. While these things are true, the receiver tube of my NP Limited Edition is 1/8th of an inch wider than the tube of the Legacy NP, and the forearm screws are not located in the same place.
The screw holes needed to move an inch back to line up with the screw holes in my rifle; and the stock above the trigger, where the end of the spring tube rests, had to be notched, allowing the stock to open wide enough to receive the larger diameter receiver — say that 5 times fast!
Anyway, the action has now been fitted into the new stock, and it makes me very happy. Although it’s Mickey-Moused in, it’s solid. While someone might notice the screws are now in a different spot, shooting yields no problems. Quite the contrary. It fits my hand wonderfully, and the trigger is easily accessed and is in a location that feels natural to me. Thank you, Crosman!
I told you about thinning the trigger in the first report. I also told you the barrel is shorter, down to 10.75 inches. [Editor's note: You did? I can't find any reference in Part 1 where you told us how long the barrel is.] I originally had plans to shorten and rethread the barrel to put the shroud back in place. I wasn’t able to get the barrel threaded; and different configurations, though effective for the noise level, were not making me happy. I found that the unmodified level of noise is not offensive, anyhow and have abandoned the attachments. The short barrel is simple and manageable. For my style of shooting, ease of movement means making the shot.
I also removed the anti-beartrap safety and can now decock the rifle. I think the ability to dencock is very important and have done so countless times already, so I’m glad I did this. [Editor's note: Removing a safety device like the anti-beartrap device cancels your warranty protection and places the liability for any accidents with the gun squarely on you.]
The trigger modifications improve performance; the shortened barrel improves performance (I believe); the stock that now fits me better improves both performance and appearance. Removing the anti-beartrap device gives me the option of decocking the gun.
Two more performance mods were applied. First, the breech seal was replaced with a nice, thick leather one. I noticed a change in the discharge sound when I did this, and it seems the gun loses no pressure at the breech with the new seal. It may have been losing air with the thin factory o-ring. The difference in contact area of the seal is about 10-fold, so I would hope it seals better!
Second, while the barrel and breech were off the gun, I opened the transfer port by just a hair, maybe one-sixty-fourth of an inch. Without a chronograph, I can only tell you these things haven’t hurt the performance. I believe they’ve probably helped velocity and have definitely helped accuracy. The short barrel and powerful Nitro Piston have the pellets hitting their marks as soon as the trigger breaks.
That brings me to the pellets. I had very little pocket change to scrape together an order of pellets, but I did manage to buy three and get the fourth tin free! I ordered two tins of Beeman Round Nose. I had good luck with Beeman Pointed pellets in a .177 Crosman TR77. At ~3 bucks a tin, these .22 domes work surprisingly well. They’re also very soft, which helps with energy transfer. They were the second most accurate pellet.
The two other tins I bought were JSB Exact Monsters and RWS Superdomes. The Monsters were bought to test the powerplant’s limits with pellet weights. My Ruger Blackhawk Elite spring rifle rebounded when a too-heavy pellet was used, and I wondered if the Nitro Piston powerplant might act the same. It doesn’t. It shoots them smoothly but not very accurately.
The most accurate pellets were the Superdomes. They also seem to run very fast. Again, no chrony, but on a super moist rainy day they were creating supersonic cracks. Shooting in dry weather they did not, so either the moisture lubricated everything to send them supersonic or wet air cracks more easily. Interesting.
The RWS Superdomes shoot like laser beams. Since I bought the NP for small game hunting, I shot a 10-shot, 20-yard group with one extra shot, a first-shot-counts test right out of the bag at a small liquor bottle (not mine, found it on the ground on the way to the shooting spot). That shot went dead-center on the 1.25″x2.5″ body of the bottle. That’s good plinkin’ in my book.
I set up a 5.5″ Caldwell Orange Peel target on the side of an old 4-slot toaster, settled in on the canvas folding sports chair rest and put ten Superdomes in a group that’s covered by a nickel. The hole in the paper target looks quarter-sized, but the holes in the toaster metal show 5/8 inch center-to-center. Two shots opened up the group, but 7 or 8 went into a little under a half-inch group.
All in all, I’m very happy with the NP. With the new stock and short barrel, I can achieve hunting accuracy out to about 35-40 yards using the pellets I’ve tested so far. If another pellet shows up that shoots better, and I keep shooting the gun well, I can see this NP easily shooting an inch consistently at 50 yards.
That’s about it. Besides a little more trigger time and work (it’s still a little creepy), the gun is in top form with no more changes to be made. I’m now just heading out to enjoy the fruits of my labor as often as possible. When I get a chrony, I’ll let everyone know to be on the lookout for part 3. Until then, thanks for reading!
by Tom Gaylord, a.k.a. B.B. Pelletier
It’s taken me awhile to get back to this pistol because I injured my hand, so I couldn’t fill the Hatsan AT P1 PCP air pistol from the hand pump for a couple of weeks, but last Friday I was at it again — probably for the last time. You may remember that I discovered that the AT P1 likes a fill pressure of 3,200 psi — which is sort of ironic in light of several recent reports I’ve done. This time, I used the Hill pump to fill the gun to that pressure to see if there are 10 good shots on a fill. That was the problem before — the circular clip holds 10 pellets, but the gun didn’t seem to want to shoot more than 7 of them on a single fill of air.
I decided that instead of wasting time with a lot of different pellets, I would concentrate on the one good pellet that I knew gave the best accuracy. That’s the Beeman Kodiak. First, I filled the gun to 3,200 psi, then loaded the clip and inserted it into the gun. Someone asked me how I held the gun to shoot it, given that it’s scoped with a Leapers UTG 3-9X40 AO rifle scope. The eyepiece has to be held within 2-3 inches of the eye in order to see the image. There’s a way to hold the gun that uses the scope as one of the handles, and that’s what I did. I photographed it for you, so you can see it as I describe the hold.
I hold the back of the scope at the eyepiece and let my hand separate the rear of the scope from my sighting eye by the required distance. My hand is pressed against my safety glasses to maintain the separation. The weight of the pistol rests directly on the bag, so all my other hand does is keep the pistol steady. With this hold, I can squeeze the trigger without moving the gun.
This hold is one I learned while shooting the LD Mark I pistol from Tim McMurray. That’s a Crosman Mark I Target pistol that Tim converts to add a longer bafrrel, a CO2 tank hanging down from the grip and a rifle scope mounted on top — just like this one. With the LD, I rested the external tank on my chest and held the scope like you see here. That gave me near-rifle accuracy.
The result is a steady hold — especially when you consider I’m shooting only 25 yards. I don’t recommend holding a recoiling firearm pistol this way, but you can get away with it on a PCP.
All targets were shot at 25 yards. The first target looked very good until the final shot. I could see that the pistol was grouping low and to the left, but all I was interested in was the size of the group. It could always be moved later with a simple scope adjustment. The group that formed looked very encouraging until the last shot, as I said. I could clearly see that one go high and into the center of the bull, ironically enough. But when I walked downrange to examine the target more closely, it wasn’t as good as it had seemed. A line of four shots appears to the right of the main group, and they’re strung vertically up to the center of the bull. The last one is the highest one. I never saw the other 3 shots in the string, so they could have been any of the preceding 9 shots. All I could see through the scope was the large group that formed at 7 o’clock on the edge of the bull.
I guess this first target took the wind from my sails. It was no better than any of the previous targets shot with this pistol. My idea that a higher fill pressure would keep 10 shots in a tighter group was bogus. But I still had time on the range, so I thought something else was in order. I adjusted the scope higher and to the right just a little, to correct for where the Beeman Kodiaks had grouped. Then, I loaded the gun with 10 JSB Exact Monster pellets. The Monster pellet weighs 25.4 grains, making it even heavier than the .22-caliber Beeman Kodiak. And it’s a JSB. I wondered if this might be the pellet that turns things around for the AT-P1 pistol.
Alas, it wasn’t. It turned things around, all right, but not for the better. The pellets were all over the place! In the end, 10 of them printed a group measuring 1.933 inches at 25 yards. It’s more of a full-choke shotgun pattern than a group shot from a rifled barrel!
Now, I was really downhearted. I switched back to the Kodiaks and give them one final try. The gun was, again, filled to 3,200 psi, and 10 more pellets went downrange. This time, the results were not as good as the first time. Ten pellets made a group that measured 1.211 inches between centers. It was higher on the target and also centered better, which proves my earlier statement that the group can always be moved by adjusting the scope, but things were not getting better.
Outcome and final evaluation
I put a lot of time and energy into testing the Hatsan AT-P1 pistol. The reward was not worth the effort, in my opinion. While I agree that Hatsan does know how to make a fine precharged air rifle, the AT-P1 pistol is not as refined as the rifles they make. It’s too large and too coarse for what it delivers. I wanted it to succeed because there aren’t that many nice PCP pistols to choose from, but the test results do not live up to the hope.
I think that if you’re interested in an airgun like thi,s you should look at the AT-P2 pistol, which comes with a shoulder stock. That way, you won’t have to learn how to hold the gun like I did here. As long as you know how few shots you’re going to get on a fill of air (7) — and you manage that, you’ll be fine.
by Tom Gaylord, a.k.a. B.B. Pelletier
Today, we’ll look at the accuracy of the Evanix Rainstorm 3D bullpup PCP air rifle. Since this is such a powerful and loud air rifle, I decided not to shoot it in my house. So, today is a 25-yard accuracy test that was conducted at my rifle range. I doesn’t matter, though, because 25 yards is the same indoors or out.
You may recall that I adjusted the trigger last time. I said I got it as light as it would safely go because the adjustment acts on the sear contact area, so this day on the range was the first real chance I had to test it under real shooting circumstances. Although it’s a little heavy at 6 lbs., 10 oz., it’s now reasonably crisp. There is no significant creep in the trigger, which for a bullpup is pretty amazing. It’s about the same as some military rifle triggers. I can shoot this rifle with no excuses.
Someone thought that the rifle would be easy to cock because the sidelever is on the right side of the receiver. Well, touch your right shoulder with your right index finger to get an idea of how easy it is. I found it best to dismount the rifle from my shoulder to cock it each time.
Another assumption I made while in my office was that the Bug Buster scope that comes with medium-high rings would work well on this rifle. Size-wise it does look good; but when I went to shoot off the bench, I discovered that the high rings will be best, after all. That’s no reflection on the Bug Buster scope — the rings just need to be higher. As it is now, I have to tilt my head severely to see the image.
JSB Exact Jumbo Heavys
While I usually begin any shooting session at 10 feet to check the scope’s alignment, this time I settled down at 25 yards and just started shooting. The pellets for the first group landed 3 inches low and 1.5 inches to the left, which is not bad for just mounting the scope and shooting without sighting in. The first group was 10 JSB Exact Jumbo Heavy pellets — an 18.1-grain dome that often works well in airguns in this 40 foot-pound power range.
The first group measures 0.574 inches for 10 shot at 25 yards. I thought that was an auspicious start for this rifle.
The rifle doesn’t move when it fires. I think that’s due to the weight, though I had a good hold on it, since I was in a somewhat odd position and had a tight grasp, just to see through the scope.
JSB Exact Jumbo Monsters
After the first group, I adjusted the scope by guesswork and brought the next group up to just under the bull I was aiming at. This was with a clip of the 25.4-grain JSB Exact Jumbo Monster pellets. This is another dome that’s even heavier than the tried-and-true Beeman Kodiaks. They acted like they wanted to group, but a couple strayed outside the main concentration, making me think they’re not the best for this rifle. Too bad; because at that weight, they really pack the punch.
Two pellets got stuck in the clip and had to be unloaded and reloaded to work right. That would be reason enough not to pick this pellet.
Next, I tried 10 of the 28.4-grain Eun Jin domes. They just barely fit in the clip lengthwise and 2 got stuck in the magazine; but if they were accurate enough, I could overlook any shortcomings just to get the extra power. Ten landed in a group that measures 0.666 inches. That’s pretty darned good when the extra power is needed.
It was time to try the Beeman Kodiaks that I thought might be one of the best pellets in this rifle. And I was right! Ten of them went into a group measuring 0.491 inches — the smallest group of the test! Don’t be misled by the appearance of this group. It does appear larger than the first group, but careful measuring shows that it’s smaller.
The last pellet I tried was the 14.5-grain RWS Superdome. It’s a very popular pellet — especially among spring-gun shooters, so I thought I’d include it in this test. Boy, what a dramatic finish it was! Ten Superdomes went into a group that measures 2.914 inches between centers! If I hadn’t shot it myself I wouldn’t have believed it after seeing all those other groups! Obviously, I’m not going to recommend Superdomes for the Rainstorm 3D bullpup!
Cool carrying case
A while back, AirForce Airguns presented me with a TalonP pistol that I tested for you. They were kind enough to put it in one of their soft carry bags, and I found that it fits this bullpup perfectly! After posting this, Edith told me that the bag is no longer being made. If you are buying the 3D, you might want to try one of the tactical bags made by Leapers. They’re about the same size and are already linked to the gun on Pyramyd Air’s site.
General impression thus far
I learned in this session that, while the Bug Buster is a wonderful scope, the medium-high rings it comes with are too low for this bullpup. Since I’ll be changing the rings anyway, I’ll use this opportunity to mount a different scope on the Rainstorm 3D bullpup.
I also learned that JSB Exact Jumbo Heavys (the 18.1-grain dome) and Beeman Kodiaks are the 2 best pellets in the test rifle. Next time, I’ll shoot these 2, plus perhaps one additional pellet I haven’t tried yet. That will be the final test at 50 yards.
The bullpup configuration was never meant to be shot from a bench. It would feel and handle much better in the offhand position, I’m sure. But the test was to prove how well the rifle shoots, which is why I shot it rested.
The long pull length is no hinderance whatsoever. I found that it supports the bullpup configuration and helps you control a rifle that’s otherwise too short.
If this is a rifle that fascinates you, I would have to say it’s probably a good one to get. I’ll still shoot it at 50 yards, but I believe today’s test shows all that you wanted to see.