The importance of bullet-to-barrel alignment and fit: Part 2
by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- An opportunity arises
- Cartridge comparisons
- At the range
- The test
- Final accuracy test
Today is Part 2 of this report that may go one more time if I don’t cover everything today. I think I won’t, because today I am reporting on a big experiment that has taken me months to complete — plus a whole lot of money!
In Part 1 I talked about the importance of the alignment of the bullet to the bore of the gun. I hope you got something from that. Today I will begin discussing the importance of the bullet’s fit. And when I say bullet, I include pellet, though there are some things that are unique to pellets that will have to be discussed later.
An opportunity arises
Several months ago I was in a local pawn shop where I saw a Taurus revolver with two cylinders. One is chambered for .22 long rifle cartridges and the other is chambered for .22 Winchester Magnum Rimfire, or WMR. I thought, “What an ideal platform to test the importance of bullet fit for accuracy, since the .22 long rifle cartridge and the .22 Magnum cartridge do not share the same bore dimensions.” We discussed this in the 4-Part series The development of the .22 rimfire cartridge.
This Taurus .22 revolver has one cylinder for .22 long rifle and another for .22 Magnum.
The .22 long rifle cartridge contains a heeled bullet that’s sized 0.2225-inches in diameter for a bore that is nominally 0.223-inches. The “heel” is a cupped portion of the bullet that sits inside the cartridge case and expands when the cartridge is fired. The heel grabs the lands of the rifling in much the same manner as the skirt of a pellet.
The .22 WMR is a more powerful cartridge that contains a conventional bullet sized 0.224-inches for a bore of the same size. While that is just one thousandth of an inch larger (0.0254 mm) than the long rifle, it is big enough to matter. That is what this report is about.
The .22 long rifle on the left has a smaller diameter bullet than the more powerful .22 Winchester Magnum Rimfire.
With this gun I had the perfect testbed to test the theory that both cartridges can’t be equally accurate, because one of them has to compromise on the bore size. So I bought it and proceeded to take it to the range.
On March 30 of this year I shot both calibers in the gun at my rifle range. But there was a big problem. More than half of the cartridges failed to fire! That was true for both calibers. It’s probably why the gun was in the pawn shop in the first place.
And, here is the big deal. Whenever you experience unreliable ignition in a firearm, you cannot depend on the accuracy you’re getting. When the powder ignites halfheartedly, the pressure curve of the burning gunpowder is thrown off and the results are sporadic. It’s like a precharged air rifle that has a velocity spread of 300+ f.p.s. No one is going to trust what a gun like that does. I had to get the gun fixed before I could conduct the test.
Fortunately I discovered a local gunsmith who is a real gunsmith — not just a parts-swapper for ARs and plastic pistols. This guy actually knows how to fix guns. How important is that? I will tell you. The local gun store allows this guy to pick up guns for repair and bring them back to the store, and they don’t charge anything for the service! You pay the gunsmith, only! But the gun store provides the drop-off and pickup place for him. That’s how important a real gunsmith is.
On top of that, the gunsmith’s services are reasonable. He examined some fired cases I gave him, plus some unfired ones where the primer wasn’t struck hard enough and determined it was either the firing pin or something in the ignition chain. Turned out to be just the pin and I got a working revolver back to test for you.
The .22 Magnum cartridge on the left has been fired 4 times without success. The firing pin marks are very light. The case on the right fired the first time.
At the range
So, last Friday I had this revolver at my rifle range. But I was faced with another problem. Do pellet guns ever shoot better with one pellet than they do with another? Of course they do, and the same holds true for firearms. How would I know if I was testing the gun with the best ammo? The short answer is — I wouldn’t. You can never know what the best ammo is until you try it all, and I had two different calibers to try!
Here is what I did. I have just three different types of .22 Magnum ammo, so I tried all three in the gun. I probably have 20 different .22 long rifle cartridges, but for this test I limited myself to just three. If this business of bullet size is real, something should show up in these few trials.
Three .22 long rifle rounds from my collection.
The only three .22 Magnum rounds I have.
I shot at 15 yards (45 feet) off a bag rest. I was seated and the butt of the revolver was rested on the sandbag. I shot five rounds of each type of ammo at a bullseye target, using a 6 o’clock hold. I used one target for .22 long rifle rounds and another for Magnum rounds. Since there were only 5 shots with each type of ammo, for a total of 15 per ammo type, it was easy to remember where each brand of ammo shot. That enabled me to select the best of the Magnum rounds and the best of the long rifle rounds. Let’s look at what I got.
Three 5-shot groups from each of the three .22 long rifle cartridges. It was for me easy to see that the Eley Tenex rounds were the best. You can’t tell that from this target, but I could as I shot it.
Here is the .22 Magnum test target. Again you can’t see which round was best, but I could. In this case it was the CCI TNT Green.
Let’s talk about the test targets. First, do you notice that the .22 long rifle rounds seem to be clustered a little tighter than the .22 Magnum rounds? There is no reason to measure the “groups” because each target was shot with 5 each of three different rounds, but the closeness of the holes overall suggests that .22 long rifle rounds will be more accurate than .22 Magnum rounds.
Second, I will go on record as being surprised that the .22 long rifle rounds hit very close to where the .22 Magnum rounds hit. There is a little difference, but not as much as I would have expected.
Final accuracy test
Now that we know the two most accurate rounds it’s possible to conduct an accuracy test. Five Eley Tenex .22 long rifle rounds go up against five CCI TNT Green .22 Magnum rounds.
Five Eley Tenex rounds made a 1.521-inch group at 15 yards, with 4 in 0.815-inches. I will address the one “flyer” in the report.
Five CCI TNT Green .22 Magnum rounds made this open 2.217-inch group at 15 yards. There is no semblance of grouping seen here.
First, let’s talk about the one flyer in the .22 long rifle target. It seems obvious to me that the Eley Tenex rounds want to group tight in the Taurus revolver. So, why is that flyer there? It wasn’t a called pull, and I think you can tell from the other 4 shots that I wasn’t making aiming errors that large.
Twenty-two caliber rimfire ammo has a history of problems with priming. It isn’t as consistent as it could be. Sometimes you get a flyer just like this one. That’s why .22 rimfire was dropped from BRV competition (a benchrest competition requiring extreme accuracy) — because air rifles were beating the pants off the rimfires! Admittedly at a closer range, but that was because of the lower ballistic coefficient of the diabolo pellet.
You might also argue that this revolver has just been fixed for faulty ignition, and maybe it’s still bad. After shooting it many times on this test day I think that problem has gone away completely. I think it is now reliable. This is all just my opinion and cannot be proven without a lot more testing, but this is what my gut is telling me.
I know this is just one little test that proves nothing. But it does give us a little insight into what I am trying to show you about the bullet-to-barrel fit. If I wanted to bowl you over I could stretch the distance out to just 25 yards and the difference between the rounds would be more dramatic.
I have a lot more to say about the fit of the bullet to the bore. Today was just the start of that discussion. We had to start somewhere.