Archive for October 2011
by B.B. Pelletier
Today we look at the groups made by the four pellets used in this test at 25 yards when the velocity is diminished. Part 4 covered the velocity for each pellet, so go there to see where each one is.
If you like nice linear results, prepare to be disappointed. Today’s target do show changes, but they may not be in the direction you expect. Let’s get right to it.
First up were the 7.1-grain Beeman Devastator pellets. These pellets have been a real surprise in this test, because they have proven to be accurate at supersonic velocity and they are not sensitive to bore conditioning. Shoot one and it tends to go to the same place every time. They also do not show any first-shot tendencies that so many other pellets do. This is a real plus for hunters, who are always shooting the first shot. I will have to return to this pellet sometime soon and test it in other guns, because it seems to be a real winner.
This group measured 0.615-inches between centers, compared to the first group in Part 3 that measured 0.743-inches. Obviously the slower pellet is significantly better, but because we only have two groups to compare it is impossible to know whether one will always be better than the other. The Devastator is still going out the muzzle at supersonic speed, even though it has been slowed by about 70 f.p.s. This is the second-best pellet of this test, just as it was in the first test.
All the shooting conditions are exactly as reported in Part 3. The scope level was used for every shot and the rifle was held in the artillery hold, with the stock resting on my hand at the same place every time. So the same care is being taken each time I shoot, and that won’t change.
Next I tried the 7.9-grain Crosman Premier lites. The bore was conditioned with four shots before shooting the group shown here, and as before, the Premiers did show some wandering in the first three shots. After that, they seemed to settle down, though as you will see, settling is a relative term.
This time the group size remained nearly the same, at 0.754-inches. The group shot when the gun was shooting them faster measured 0.778-inches, which is too close to call. Yes, the group fired with the pellet going slower is a trifle smaller, but it is really too close to say there is a difference that’s due to the velocity — especially given the built-in error in measuring groups that I have talked about.
The third pellet I tried was the heavier Beeman Kodiak. They turned in the best group of the test, just as they did the first time. And the ten-shot group measured 0.628-inches between centers, which is very close to the 0.633-inches of the first test.
I cannot say that the Kodiaks did any better this time than they did in the first test. Even though the velocity was slowed by 55 f.p.s., it doesn’t seem to make much difference at 25 yards. Maybe that’s just not enough of a drop to matter.
The last pellet tested was the 16.1-grain Eun Jin dome. These pellets were never in the transonic region, even with no transfer port limiter in the gun. So this time they were just going slower. And what a difference that made!
Ten Eun Jin pellets were all over the place at 25 yards. They made this huge group that measures 1.118-inches between the centers of the two pellets farthest apart. This is the worst group of this test and also much worse than the first test with this same pellet, when they grouped 0.798-inches.
Eun Jins made a bad showing at 25 yards with the transfer port limiter installed. As long and heavy as they are, I guess they need all the velocity they can get, to obtain the rotational speed required for stabilization.
What have we learned?
The first thing we learned is this probably was not enough of a velocity drop to matter, except for the slowest pellet. The next thing we learned is that the changes are not always linear. Although three of the pellets exhibit what I would call a linear relationship of accuracy to velocity, only one of them — the Beeman Devastator — shows any real improvement. And even that is just a very small improvement that could just be due to chance.
The next thing we learned is that some pellets need their speed to maintain accuracy. The big heavy Eun Jins do not like this lower velocity, and I will predict they are going to get even worse with the next velocity decrease.
The Crosman Premiers are still not performing well, and since they are still within the transonic region, there is good reason for that. I look for an improvement in the next test.
What all this tells us is that using very long heavy pellets in a lower-powered airgun is probably not a good idea. When the distance to the target increases beyond about 30 feet, you will start seeing these pellets spread out, where lighter pellets will probably continue to be accurate.
by B.B. Pelletier
It was a blustery day at the range this past Wednesday. Texas is noted for being windy most of the time, and this day was a classic. I noticed it while loading my truck at the house, and when that happens it never gets any better. Today I would be shooting the TalonP air pistol at 50 yards — a challenge to any airgun, and certainly in this wind it would be an acid test.
Once I got to the range about 15 miles away the wind was still blowing, even though the entire range facility is set in a small valley. The 50-yard range has a solid 12-foot-high earth berm all the way down to the backstop on both sides, so the wind really has to blow to affect you. But it was. My shooting glasses blew off the bench and a sack of loaded centerfire cartridges did the same. Nothing was safe.
By the time I had everything set up the wind was gusting to 15 mph and blowing at least 5 mph during the lulls. So I thought about writing the day off and doing something else. But this was the first time I had the TalonP pistol at this range and I really wanted to salvage something out of all the effort.
However, I didn’t have an especially accurate pellet for the gun yet. Beeman Kodiaks were the best I had tested so far and, as many readers had pointed out after reading Part 2, they were only average. I figured I could find a sweet spot in the pressure curve where the Kodiaks would perform at their best, but I really had hoped for a better-performing pellet for this test.
No great .25-caliber pellets
But the odds were against me. You see, there has never been an especially accurate .25-caliber pellet. It is the one caliber of all four smallbore calibers that really has no pellets of note. Oh, they are okay for hunting at close range, but they simply cannot compete with the superb accuracy that some of the premium .22-caliber pellets give at longer distances. And, since the TalonP only comes in .25 caliber at this time, I needed to find a .25-caliber pellet that worked — even if it was only satisfactory and not really notable.
Years ago RWS imported a .25-caliber pellet called the Diana Magnum. It was a 21-grain dome and it showed real promise in my Whiscombe. Shooters everywhere thought the Diana Magnum was the best .25 caliber pellet ever made. I have a couple tins of them in reserve, but what’s the purpose of showing you a great pellet that you cannot buy? I needed something that worked and was available.
So hoping against hope I took some of every decent .25-caliber pellet I had to the range — in hopes that one of them might miraculously work. When I began shooting, the wind speed had increased. Now the gusts were as high as 25 mph and I had to wait a long time for a 5 mph lull. So I shot into wind moving 10 mpg and hoped one of the pellets I had brought would somehow be able to buck the odds.
Since I already knew how well Beeman Kodiaks and Eun Jin heavies do, I began shooting with Beeman Silver Arrows. No dice. They flew everywhere. Then I tried the Beeman Ram Jet pellet that is apparently no longer available in .25 caliber. Another loser.
Then I spied a tin of JSB Exact Kings. These are relatively new to the .25-caliber world, but JSB has a solid reputation for making some of the world’s best pellets in the other three calibers. I hoped their expertise carried over into the quarter-inch bore.
And it did! The second shot went into the same hole made by the first! I didn’t start celebrating, but things definitely looked better, because when two pellets go into the same hole at 50 yards on a windy day you are onto something! So I kept shooting that pellet and hoping it might be the one. The first hole with two pellets was soon followed by another two pellets in the same hole when the aim point was changed. This was looking promising.
A bunch of random holes scattered over the 50-yard target until, bam! Two pellets went into the same hole (bottom left). Then I selected a different aim point and, bam! Two more pellets in the same hole (upper left). Was I on to something?
I set the power level of the pistol on eight and refilled the gun to 3,000 psi. I know this should give at least 10-12 good shots, but since I hadn’t tested this pellet through the chonograph yet, I couldn’t say much more. Then I adjusted the Hawke scope and tried to shoot a group of ten. This time I got what would be a decent group for any .25-caliber airgun. Ten shots went into a group that measured 1.242-inches. Given the wind that was now gusting most of the time, that seemed pretty reasonable, however within the 10-shot group were two separate smaller groups that baited me. This gun had more to offer.
I refilled the reservoir then switched targets to a larger bull and shot another ten-shot group. This was the one that got me so excited! Although it is larger than the first group, at 1.343-inches overall, there are nine pellets in a group measuring 0.817-inches. That’s at 50 yards on a blustery day! No reason for the stray shot except the wind. But look at the nine! That would be good performance from any PCP on a calm day. This pistol really wants to shoot.
There it is. The group that caused me to reschedule today’s report. This is outstanding performance from any air rifle at 50 yards on a windy day. Note the group is strung horizontal by the wind. No excuse for that lone pellet hole. That’s just where it went.
The next step is to get out on a better day and shoot at 50 yards again. I won’t be testing any other pellets, because I’ve found the one that works. I know how that reads when you are sitting there wanting to know absolutely everything about this airgun, but here is the deal. I have shot enough .25-caliber airguns to know great performance when I see it. And this is it. You won’t get a group like that from Kodiaks, and as for the rest of the pellets on the market — good luck. If I were going to hunt with the TalonP, I would lay in a good supply of these JSB Exact Kings and go with it.
I also want to chronograph the pistol, but not in my office! I need to be out at the range to shoot a gun that is as potentially loud as a .22 rimfire.
The shoulder stock
AirForce loaned me the optional shoulder stock extension you see in the photo and I used it for this test. I discovered that the scope was positioned too far to the rear, so I relocated it during the test. The shoulder stock works very well, but the smaller size of the pistol’s reservoir means you need to find an alternative placement for your cheek when firing. It took a while but I found a hold that works for me and the last group was shot with it.
The really good news
I know the folks at AirForce will celebrate the performance of the JSB pellet in their gun, and for me finding this pellet is just as major as discovering how well the pistol shoots. I am reminded of the movie Back to the Future, Part III in which Doc Brown was trapped in the year 1885 with his DeLorean time machine and no gasoline. He had the greatest vehicle in the world, but without gas it was going nowhere. Well, the .25-caliber airgun world just got gas, in the form of this JSB pellet. Finally there is a no-apologies pellet that can hold its own with a .22 at distance! I think I will have to explore this pellet’s performance a little more in the future.
I was also able to retrieve several fired pellets from the thick rubber backstop and from their appearance it can be seen that they hit with a lot of force. I think this will make a good long-range hunting pellet.
The rest of the day
Just to put this day into perspective, my shooting partner shot a half-inch ten-shot group at 50 yards with one of those hyper-accurate .22 HM2 conversions he makes, but when we moved to the unprotected 100-yard range, a FIVE-shot group blossomed to 1.5-inches!
My .250 Savage that shot five shots into 0.8-inches at 100 yards last time shot three into 1.25-inches this time. The day was just too windy to do well with anything. And that is why I did not even bother shooting the Ballard.
by B.B. Pelletier
Today we lower the velocity of the Whiscombe and test each of the four pellets, in preparation for the next accuracy test.
One reason I selected the Whiscombe for this series of tests is the fact that I can control the power output over a wide range of velocities by installing various transfer port limiters. For those who are new to airgunning, every spring-piston airgun like the Whiscombe generates a brief blast of compressed air by means of a piston racing forward in a compression tube. In the Whiscombe’s case it is actually two pistons racing towards each other. At the exact end of their travel a small air tunnel called an air transfer port conducts the compressed air from the compression chamber to the base of the pellet, where it blows it out the bore.
The amount of compressed air is extremely small, but the pressure is fantastically high for a brief moment — as much as over 1,000 psi. In fact, well over 1,000 psi. Now you probably also know that precharged airguns operate on compressed air that is at an even higher pressure, but the difference is, when a precharged valve opens, it does so relatively slow, releasing air at far below the pressure that’s in the reservoir. But a spring piston gun doesn’t have any valves, so when the air is compressed, it flows through the air transfer port to the back of the pellet like a small explosion. Everything the gun has to give is right there at the same time.
However, if anything gets in the way of this air as it flows, it slows down the flow and the resultant energy output of the gun. The amount of compressed air remains the same, but the rate at which it flows is slower, and the pellet is not moved with the same sudden push.
That’s a fancy explanation for the Whiscombe’s air transfer port limiters, which are nothing more than Allen screws that screw into the threaded transfer port. In the center of each are holes of various sizes though which the air must then pass.
The rifle has a threaded air transfer port. It’s shown here without any limiters installed.
These limiters have various sized holes that reduce the airflow through the transfer port when they are installed. For this test I will install the largest one on the left.
The transfer port limiter is installed with an Allen wrench.
Now let’s see what changes have been made by the insertion of the transfer port limiter. I will shoot the same four pellets as before and in the same order.
First I tested the Beeman Devastator pellet. This is the pellet that gave an average velocity of 1,205 f.p.s. in Part 1 without any transfer port limiter. With the limiter I show being installed above the Devastator’s average velocity dropped to 1,123 f.p.s. In the first test the spread was 28 f.p.s. In this test is was 16 f.p.s., running from 1,116 to 1,132 f.p.s. That isn’t a huge drop in speed, but the power that was 23.32 foot-pounds in the first test has dropped to 19.89 foot-pounds. We will see what this does to the accuracy.
Next came the Crosman Premier lite pellet. In the first test they were averaging 1.134 f.p.s. for an energy of 22.56 foot-pounds. The spread in that test was only 12 f.p.s. In this test the same pellet averaged 1,057 f.p.s. for an energy of 19.56 foot-pounds. The spread was an even tighter 6 f.p.s., running from 1,054 to 1,060 f.p.s. That is incredible performance at this power level.
Beeman Kodiaks came next and they averaged 992 f.p.s. in the first test. That generated an average 22.29 foot pounds of energy at the muzzle. The spread in test one was 22 foot-seconds. After the transfer port limiter was installed the average velocity dropped to 937 f.p.s. for an energy of 19.89 foot-pounds. The total velocity spread was 24 f.p.s. — ranging from 927 to 951 f.p.s.
The heavy 16.1-grain Eun Jin was the final pellet I tested. In the first test they traveled 726 f.p.s. and generated 18.85 foot-pounds of energy. The spread was 13 f.p.s. With the transfer port limiter installed they averaged 687 f.p.s. for an energy of 16.88 foot-pounds. The spread with the limiter installed was 10 f.p.s. — from 682 to 692 f.p.s.
Next I shoot groups at 25 yards with each of these pellets so we can compare them to the groups fired with no transfer port limiter. That will give us our first look at how velocity affects accuracy.
After that I install another limiter that restricts the airflow even more, so the rifle shoots slower. And then we shoot it at that level for accuracy.
At the end of this test I still have one pellet out of four that’s supersonic. The Devastator, at 1.123 f.p.s. will always be supersonic where I live. The Crosman Premier, however, will be right on the cusp of the sound barrier and whether of not it breaks though will depend on the day.
Normally I would run the accuracy part of this report immediately after the velocity report, but something wonderful happened at the range on Wednesday. So I am making a special report on Friday to show you something very amazing — at least in my eyes. And no, it isn’t the Ballard. Not yet.
by B.B. Pelletier
Believe me — there’s enough information on this topic to fill many reports. I will do that if there’s enough interest; but if interest is confined to just one or two people, I’ll recommend that you read several of the gun books that I listed in my Building an airgun library blog.
Those books present and discuss several ways of target measurement that are considered outdated today, but which hobbyists keep trying to reinvent. One is the old string measurement in which a piece of string is stretched between the center of the target and the center of each bullet (pellet) hole. The cumulative length of the string then determines the cumulative distance of all the shots from the center point of the target. This system of measurement was popular in the late 19th century, having replaced a simpler method in which the string was stretched around pegs placed in all the bullet holes and gave the “circumference” of the group.
That small paragraph is all I’m going to say about these older group measurement methods unless I see a reason for more. Today, I want to concentrate on how groups are measured and reported these days.
Here we go!
Are you just a little bit anal? Don’t answer that. Because you’re an airgunner, we can tell there’s a missing chromosome in your DNA that drives you to examine minutiae and project worlds onto what you see. Please don’t be insulted, because look who’s talking — Mr. “The atomic clock in Denver may be accurate, but everyone knows that it’s off by just a little!”
I feel the tightness of your headband when you’re confronted by numbers. Know what I do about it? Like every other gun writer — I lie (sort of…although most people wouldn’t call it lying). I give you numbers out to three decimal places, knowing that you will focus on them as though they have been transcribed from court records. What I seldom do (other than right now) is admit how far off those numbers might be. So, today, is honesty day and I’m going to tell you exactly how I measure targets.
Oh, and by the way — there’s only one other way of measuring targets that is any more accurate than the one I will show you, and that is sound measurement. At world cup and Olympic matches, the targets are scored by sound transducers that triangulate the sound of the pellet tearing through the target paper to extreme precision. But at U.S. National Junior Airgun Matches I’ve attended, they guess at the location of the pellet holes just like I do. Yes, I said guess, and anyone who disagrees with me will be sent outside to meet with my friend Mac!
There! Have I upset everyone? If not, please leave a comment, and I’ll insult your children, spouse and pets.
Here’s the deal. Determining the location of pellet holes today is a bit like invoking the Heisenberg principle, in which that which we observe is also altered. The most formal way of doing it today (other than the sound measurement mentioned above) is by sticking a plug called a scoring gauge through the pellet hole and looking through the magnifying edge of the plug to see what is the highest-scoring ring touched by the pellet. In international competition, the line must be broken by the pellet. It’s a subtle but important difference.
For a great article on scoring gauges, read Gary Anderson’s article located here. Gary is the Director Emeritus of the Civilian Marksmanship Program (formerly the Office of the Director of Civilian Marksmanship) in the U.S., and he’s also a double gold medal Olympic high-power rifle champion. He has had his targets scored more than once and is most familiar with the problems of the sport. It was through him at the now-defunct Winston-Salem Airgun Exposition that Edith and I were first exposed to sound-scored targets.
These gauges or plugs can and almost always do enlarge the holes left by the pellets, so it would be possible for an unscrupulous person, like a team coach, to “scooch” the plug in the direction that best supports his team when he inserts it in the hole. Or, if you make the coaches of the opposing teams score each other’s targets, the elongated holes will run the other way. Don’t think it doesn’t happen — I have seen opposing coaches almost come to blows over how the targets are scored. At the national level, they don’t allow coaches anywhere near the scoring until the deed is done. Then, they get to examine their team’s targets and argue for any close calls they find. And they DO argue!
Another way to score a target is the optical method, in which a device is used to locate the pellet hole without damaging it. I have owned and used an Eagle Eye device for the past 15 years, and it works quite well — except for one thing. You are still GUESSING where the pellet hole is when you do it this way. It works good enough for regional-level matches where the targets have scoring rings set at prescribed distances, but only for calculating the score — not for measuring the size of shot groups — which brings us back to today’s topic.
How to measure group size
The method I’m about to explain is the same one that was used by Harry Pope at the turn of the 20th century. It is simple, fast and easy to do. It’s also open to interpretation and small errors. Are the hairs standing up on the back of your neck, yet?
You measure group size by bracketing the group with a dial caliper, so that one jaw touches the extreme edge of one hole and the other jaw touches the extreme opposite edge of the hole farthest away from the first hole.
The big question
Here’s the question many of you have asked in the comments to this blog, and many more have wondered privately: How is it possible to identify the exact edge of a pellet hole with a caliper or any other measuring instrument?
It is not possible to locate the exact edge of a pellet hole with a measuring instrument — whether it be a dial caliper or the index marks on a ruler. The hole is insubstantial, and you’re trying to measure it as though it was solid. It can’t be done — not with great precision, anyway.
But once you do your best to find the closest measurement across the two widest holes, you’re left with a number that has two or three decimal places. It sounds or reads like you have great precision, when in fact the best you could do was make a guess where the boundaries of the holes were. Harry Pope struggled with the same thing a century ago, and there is nothing anyone can do about it. Pope wore two pairs of glasses and also used a magnifying glass to measure his targets, and he still was only guessing at where the shot boundaries were. He took as long as 30 minutes to carefully examine important targets this way. I seldom take longer than a minute, and frequently a lot less than that.
So, all of us gun writers continue to bracket our groups with dial calipers and make a best educated guess where the edges of the two outlying holes are, then we subtract one pellet diameter and give you the number. We subtract one pellet diameter because what we really want is to measure the distance between the centers of those two pellet holes. Subtracting one pellet diameter from the overall reading takes half the diameter away from each of the two holes we used to bound the group. Thus, we get to the centers.
The bottom line
I resolved not to obsess over this issue years ago; because if I couldn’t get past it, I couldn’t write about guns. In the same way that I know that chronograph readings are also not exact, I know that the closest I can come to an exact measurement on paper is probably 0.005 inches, when everything goes my way. But give me ragged BB holes to measure and a paper target that rips instead of showing clean holes, and the error is probably closer to 0.020 inches. And that’s on a good day, when I am really trying my hardest.
But the number I publish will always have two or three decimal places, and it will look official to everyone.
Here’s an exercise that will illustrate the dynamic I’m explaining. Which sounds more precise — 3/4-inch or 0.750 inches? If you’re honest with yourself, you know the decimal fraction sounds more exact. The point is that both of them are being obtained from a system that has built-in tolerances for slop!
Think you can measure this group to the nearest thousandth? Bully for you, because this is as easy as it ever gets! You will always be off by as little as 0.005 inches and as much as 0.020 inches when the holes are this clean. These are holes left by wadcutter target pellets.
Now where are the holes? This is what domed pellets look like close up. Where are the edges?
I need a vacation! This is what slow-moving BBs do to a target that’s been attached to a cardboard backer. Guess where the holes are?
I’m sure many of you knew this already and didn’t need to be reminded. But from some of the comments I’ve been seeing recently, I was concerned that some of us are getting hung up on the numbers — as in accepting them at face value. These numbers are a best guess and are published with the best of intentions, but they are, and always will be, a little off.
Here’s what you can say about such numbers. A 0.36-inch group is unquestionably tighter than a 0.511-inch group. Even when the first group is shot with .25-caliber pellets and the second is shot with .177-caliber pellets, so the two groups appear very much the same, the first one is still tighter.
What I’m saying is that these numbers can be used as relative measurements. Just don’t stake your career on them. This is one more good reason why I shoot 10-shot groups when possible. Not because the measurements are any more precise, but because there are always more opportunities for the gun to mess up. If all 10 holes are in close proximity — even if my estimate of how close is wrong — you still have a good idea of how well the gun is shooting.
by B.B. Pelletier
Today is the day we answer the long-awaited question of how accurate the Smith & Wesson M&P 45 air pistol really is. Is it capable of shooting out a one-inch bullseye at 23-24 yards, as one owner claimed, or does it conform to what we know about this level of air pistol?
Two different types of ammo
For starters, this pistol shoots both BBs and pellets. Usually when a gun does that, it has to give something away for the compromise, because BBs are much smaller than pellets. They are also made of steel and cannot take the rifling; so when you shoot a BB, you have to shoot it as a smoothbore. I tried them first.
BBs — not that hot
As expected, eight BBs did okay at 25 FEET. Nothing spectacular, but eight shots did land in a group that measures 1.747 inchs across the two widest centers. That’s minute-of-pop-can accuracy, but nothing more. I shot Daisy zinc-plated BBs for this.
I did discover during this session that the sights needed a lot of horizontal adjustment. The group of BBs at 25 feet was slightly low and three inches to the left. I loosened a locking screw on the rear sight and slid it to the right to correct this, and it took two corrections to get it right. When the shots were centered on the bull the rear sight was noticeably over to the right.
Now, on to pellets
I had suspected that it wouldn’t be BBs that were so accurate, but lead pellets. So I was all set for a surprise when I shot them. The distance to the target was 25 FEET from a supported standing rest. I shot single-action and I can report that my eyesight has returned to about where it was in the past.
I shot many different types of pellets, but two stood out enough to be worthy of mention. The first were H&N Finale Match Pistol pellets. They shot to the point of aim and grouped well, though there was always one or more that opened up the group.
I actually shot several groups of this pellet, because they were teasing me with groups that were almost perfect, but never quite. Finally I came to the conclusion that we are seeing the best the pistol can do with the two groups I’ve selected to show.
The other pellet that really did well were JSB Exact RS domes. I tried them because they are lightweight and very accurate in lower-powered air rifles, so I thought that might carry over to pistols.
Apparently, it does, because one of the many groups I shot at 25 FEET was the best of the session. Eight pellets went into a group measuring 0.928 inches.
Although this group is the smallest of the test, don’t be mislead by the appearance. There is a ragged hole at the bottom of the bull to the left of the number six that enlarges this group to 0.928 inches. That’s good, but not that much better than H&N Finale Match Pistol pellets.
Here is another target shot with JSB RS pellets that will fool you. It looks great, but a stray shot that cuts the five-ring (to the right of the dime) enlarges what looks like a tight group to 1.342 inches.
What is the conclusion?
Is the S&W M&P pistol capable of one-inch groups at 23-24 yards? Of course not. It would be one of the most accurate pellet pistols on the market if it were. But at 25 FEET it is more accurate than I expected. Especially with JSB RS domes and H&N Finale Match Pistol pellets. This gun wants to group.
I didn’t shoot at 25 yards because there is no point. It will probably group eight shots in the 3-5 inch range if everything is done right and the best pellets are used. I don’t think this pistol gives us any surprises other than it is very capable for a blister-packed air pistol.
At the price, I doubt you’ll find a more accurate pistol capable of shooting both BBs and pellets — and that says something. With Christmas coming soon, maybe this is one for your gift list.
by B.B. Pelletier
I’m writing this report because I saw from the comments on the accuracy versus velocity test that several readers do not know what a scope level does. And where three people speak out, there are three hundred who are reading and remaining silent.
They say that there’s nothing more zealous than a convert, and I expect that is true of me when it comes to scope levels. I have understood their need for a long time and even conducted a fairly extensive cant test back in my Airgun Letter days, but it was my .38-55 Ballard single-shot rifle that really drove the message home. That rifle came with a bubble level, and it’s far more precise than the levels we find on air rifles today. The bubble moves very slowly, making it important to check the level just before you begin the squeeze; because what looks like a level gun one moment can change slowly to a canted gun if you don’t watch the level. By contrast, the scope levels I’m using with airguns have bubbles that move very fast, are much easier to see and are far simpler to work with.
Today, I want to demonstrate the effects of using a bubble level. I’ll use the same Whiscombe JW75 that I’ve been using for the velocity versus accuracy test, because we already know it has an accurate pellet in the Beeman Kodiak. For this test, I first seasoned the bore with six shots, then fired a group of pellets with the bubble deliberately off-center in both directions. I fired a second group where I paid no attention to the level and just tried to level the rifle as best I could through the scope. The final group was shot using the level with the gun absolutely level for each shot. The distance was 25 yards, which several readers mentioned is almost too close to see the effects of using a level.
This is the insidious part of leveling a gun, and it’s what I’m showing with today’s test. You really can’t see a pattern to the group from not leveling the gun when you’re shooting as close as 25 yards, but you can see that there’s a difference between a level gun and one that’s not level. We’ll get to that in a moment.
What the level does
The scope is mounted above the barrel, so it’s adjusted to look through the trajectory of the pellet so that the point of impact coincides with the aim point at a certain distance from the gun. However, if you tip the gun to either side and then sight it, your crosshairs will still be on the point of aim, but the barrel will no longer be directly below the scope. It will be to one side or the other, depending on which way the rifle leans.
Our intrepid blog reader duskwight was kind enough to give us a link to a superb animation of this phenomenon. You will find it here. Someone (Wulfraed?) said that a gun will describe an arced impact point if the cant is shifted through an arc, left to right. That’s exactly what the online animation shows, and it’s exactly what a scope level does for you.
One reader asked if the scope level would still make a difference if the scope had been optically centered. Yes, it would. There’s no relationship between optically centering a scope and using a scope level. The former simply allows you to adjust the elevation for different ranges without the shot group moving from side to side because the scope stays centered all the time, while the latter relates to how the scope and rifle are actually held when fired. The first is optical, and the second is physical.
The test is straightforward. First, I seasoned the bore with several shots. Then, I fired a group of 10 shots at 25 yards with the rifle canted to the right for 5 shots and to the left for 5 shots. The cant was controlled by the position of the bubble in the level, and I stopped tilting the rifle the moment the bubble came to the end of its travel. Obviously, there’s some error in this, as the bubble level is not a precision instrument, but I think you’ll get the idea.
And here’s the group. Do you see that you cannot tell that the rifle has been purposely canted in two different directions? This just looks like a large group for a Whiscombe at 25 yards. Group measures 0.905 inches between centers.
Next, I shot another group of 10, only this time I completely disregarded the level. I just shot and tried to hold the gun level from the visual cues seen through the scope. This is the same way I shot the rifle during the initial accuracy test.
For this group of ten Kodiaks I disregarded the level. I tried to keep the rifle level by visual cues through the scope, but that was all. Group measures 0.874 inches between centers — or not much better than when I was purposely canting the rifle in two different directions. Also note how much like the first group this one looks.
For the last group I leveled the rifle for each shot. I was also careful to hold the rifle exactly like I was holding it for the other two groups. The results are very telling.
This group of 10 Kodiaks was shot with the rifle leveled each time. It measured 0.624 inches across the centers; however, if the stray ninth shot is omitted, it would measure 0.36 inches. If you check the last accuracy test I did with Kodiaks on Friday, you’ll see that this result is very close.
I’ve seen this same test result repeated numerous times over the years, so I don’t feel the need to run multiple groups and do a sample of each type, but you’re free to do so. I know this is what happens when a scope level is used, which is why I used one when I competed in field target.
You might ask why I don’t always use a level when testing airguns. The short answer: time. It takes a lot longer to settle down and check everything when you shoot this way, and I don’t think it’s always necessary, anymore than I would use a minute-of-angle rifle in a firefight. An AR 15/M16 is fine for that kind of work. But when real accuracy is on the line, a level brings out the very best a rifle has to offer.
by B.B. Pelletier
What a day we have before us! I relearned a valuable lesson in accuracy and got some very surprising results.
Increasing accuracy by an order of magnitude
Before I launch into today’s report, a comment I made a few days ago has raised some interest and I thought I would explain it now. I happened to mention that a new loading technique that I was trying on the Ballard .38-55 rifle had given me the promise of an accuracy increase of an order of magnitude. Instead of 10 shots going into one inch at 100 yards, it looks like this new technique will be capable of putting those same 10 shots into one-tenth of an inch at the same distance. Whether I ever accomplish such a feat is immaterial as long as the rifle demonstrates it can do it.
The technique is one I found in the book Yours Truly Harvey Donaldson. He reported on it in the 1930s, and it’s a technique that was used before the start of the 20th century. And this only applies to lead bullets — not jacketed bullets. The technique is to load the bullet directly into the bore of the gun so that it stops about one-sixteenth of an inch in front of the loaded (but bulletless) cartridge. You do this with an empty case into which a hard wood dowel is driven, then cut off one-sixteenth of an inch longer than the end of the case.
Then simply drop the lead bullet into the chamber with the muzzle pointed down and insert the doweled cartridge behind it. A tool with a lever can be made to seat the cartridge deep enough into the rifling that the rifle’s breech can be closed, camming the bullet the last bit of the way into the bore. Extract the doweled cartridge and insert a loaded cartridge behind the bullet.
The loaded cartridge is reused for every shot — thus eliminating one variable. The cartridge is de-primed, the primer pocket cleaned, re-primed, loaded with a light charge of powder (10 grains of Unique for my proof of concept test) and the balance of the case is filled with Cream of Wheat cereal. Shooters have been loading with Cream of Wheat this way since at least the year 1900, and it works. I put a cork wad on top of the Cream of Wheat, and the cartridge is ready to fire. The cream of Wheat keeps the hot gasses from the base of the lead bullet, so you can use very soft lead that fills the bore better.
It takes approximately 5 minutes to go through the entire loading process; but in that time, the barrel has an opportunity to cool down. Thus, giving stability to the rifle. Because it will go back into the same chamber from which it was extracted, it doesn’t have to be resized. I filed a notch on the rim of the cartridge and this notch is oriented to the 12 o’clock position, to allow the cartridge to enter the chamber the same way every time.
As I mentioned in my comment, the first two shots from my clean rifle went about three inches apart, with the next three going into two-tenths of an inch. That’s at 100 yards with open target sights and a bubble level. I will be reporting on this process in much greater detail, and I’ll have photos for you to see what’s going on in a future report; but I wanted to satisfy the curious who have been asking me about what I’m doing.
On to today
Well, the stuff you just read had a lot of bearing on today’s test. You may remember that this is a retest of the four pellets at ultra-high velocity — which is as fast as any spring gun can propel them. The objective of this test is to see if lowering velocity has any effect on the accuracy of these four pellets.
I’m doing a retest because I thought that the first time around I detected some evidence of group shifting as the bore got seasoned to each pellet. Two of the pellets seemed to act that way, while the other two didn’t.
But as long as I was doing the test again, I decided to use the scope level that’s mounted on the Whiscombe rifle I’m using. I have learned from shooting my Ballard rifle, which has a bubble level on the front sight, that leveling the rifle for each shot makes a huge difference in accuracy. However, that’s at 100 yards, and I’m shooting the pellet rifle at 25 yards. Could a level help much there? I wondered, so I tried it.
I shot the pellets in the same rotation as in the first test — lightest to heaviest. So first up was the Beeman Devastator.
You may recall that I selected the Devastator because it’s the kind of hyper-fast pellet I figured guys who buy hyper-velocity air rifles might choose. I didn’t expect it to be accurate, but you’ll remember that it was.
The Devastator was also one pellet that showed no need for bore seasoning. In other words, it was ready to go from shot one. I was prepared today to shoot four pellets (three to season the bore and a fourth to check where the group should be) before moving to a fresh target, but the Devastator shot so well that I didn’t do that. Today’s group is the first 10 shots out of the gun.
Incidentally, the shot that strayed from the main group was No. 4. But all the others were even tighter than the group size indicates. I hope you can understand why I did not feel the need to shift this pellet after the first three shots.
Devastators still crack like a .22 rimfire because of the sound barrier thing, so they’re not the pellet to use in the backyard. At least not at this velocity. But they’re accurate. In the first test, the group measures 0.903 inches, so this isn’t really that great a reduction, but I do believe that the small improvement was due to my using the scope level on the rifle for every shot.
Crosman Premier lites
Next to be tested was the Crosman Premier lite pellet. In the first test this pellet was the one that gave a huge difference between where the first couple shots landed and the main group went. So I did season the bore with three test pellets and a fourth check pellet, just to see if the group moved. And it did. It moved about a half-inch upward.
What a difference from the first time! The first group of 10 Crosman Premier lites at 25 yards measured 2.385 inches between centers. This one measures 0.778 inches. Seasoning the bore with four warm-up shots before shooting the group made the largest difference, but the scope level also helped.
Many of you expected Beeman Kodiaks to be the best in this test the first time. They were good, but not quite the best. Well, this time they turned the tables and made the best group. I seasoned the bore as described with four shots before starting this group; and although it was small, I did see some movement from the first shot to the second. It’s difficult to say whether that was due to seasoning the bore or just general dispersion, so I’ll withhold comment.
The last pellet I tried was the 16.1-grain Eun Jin dome. In the first test, this was the most accurate pellet, but this time they slipped to last place. Ten went into a group measuring 0.798 inches. However, that’s very close to their first group of 0.755 inches, so they really didn’t change that much — if any. The others just passed them by.
I now feel confident that I’m getting everything this rifle has to offer from these four pellets at this velocity. Seasoning the bore remains iffy. It seems to help Premiers, but pure lead pellets don’t seem to need it as much — if any. However, adding the scope level made a big difference in group sizes.
Now the bar has been set; and according to my expectations, it’s set high. Every time I run this test, I’ll have to shoot my very best if the results are to mean anything.