Pellet velocity versus accuracy test: Part 3
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.