Another twist on rifling
by Tom Gaylord, a.k.a. B.B. Pelletier
I thought I’d provide some thoughts on how this blog has helped me become a better shooter. We just finished the Twist-rate test last week, and I wanted to share with you some things from that test that have impacted my shooting.
I’ve been using the output of the test to guide my own shooting with both firearms and airguns. I did test the swaged bullets in my muzzleloader already, but I discovered that there’s a lot more to learn. I can’t get the bullets I’ve swaged to group at 50 yards to save my life! I get maybe 1 out of 3 shots to land on paper. I think the problem is that I’m driving them too fast. I’ve been using the same load of black powder that I use for a patched ball, which seems like double the amount needed to get good results. When these bullets are fired in airguns, they’re shot at between 400 and 650 f.p.s., and I’ve been launching them at 1,000 to 1,200 f.p.s. I think I’m blowing them apart!
I plan to load less than half the amount of black powder to see if I can get the velocity down around 650-800 f.p.s. The twist-rate test told me these short bullets don’t need to be spun up as fast as I’m shooting them. At least, I think that’s the case. More later when I actually have something to show you.
A friend talked me into buying some Accurate Arms 2230 powder for my AR-15, but when I tried it with the 69-grain and 77-grain bullets I normally shoot, it was lousy. The burn rate of this new powder is way faster than the Varget and Reloader 15 powders I’ve been using, and both given such good results. I figured the problem was that I was trying to push a bullet that was too heavy with a powder that was too fast.
I still can’t get over how accurate my AR-15 is with the right loads.
Ten shots into 0.54 inches at 100 yards is pretty good for an AR-15.
I loaded some lighter 55-grain bullets with the lowest charge of 2230 the book recommends. But the results were poor, again. Oh, they were twice as tight as before, when I shot the 77-grain bullets; but with 10 shots going into 1.808 inches, they still aren’t worth the trouble. It may be that my 1:8″ twist is just too fast for lightweight bullets, but I still need to experiment some more.
Ten rounds into 1.808 inches at 100 yards is terrible for a rifle that can do so much better.
I updated you on the Ballard situation a few weeks ago. I told you that I discovered the Ballard’s rifling has a twist rate of 1:20″, while Winchester rifles of the same caliber (.38/55) have twist rates of 1:18″. Given the slow speeds I shoot, the difference is significant. Bullet molds and cast bullets that are available today are all made for the Winchester, which is far more common than a vintage 1886 Ballard.
My vintage Ballard turns out to have a twist rate that’s on the slow side for the bullets that are available.
What this means is that I’ve been trying to shoot with bullets that are too long and heavy for the twist rate of my rifle! It took the results of the twist-rate test to drive this fact home. The solution is not as straightforward as it sounds, however. You might think I could just have a custom mold made for a shorter bullet. That’s possible, but I first need to think some things through. For example, would the rifle do better with a full charge of black powder and the bullets that I already have?
I got very discouraged when I learned that my rifle had a slow twist rate. I even considered selling it and buying a rifle that was more suited to what I want to do — which is shoot 10 shots into less than one inch at 100 yards with non-optical sights. But when I tried to list the rifle for sale, I found I could not let it go!
No matter what I do, I just cannot seem to get the Ballard to group much better than this at 100 yards. Ten went into 2.654 inches.
So it’s back to the beginning with the Ballard. I have to figure out how to make this old beauty shoot in its current form because it is too valuable to modify. And everything I do from this point forward will be driven by the slow twist rate!
The next twist-rate test
We’ve finished the initial twist-rate test, but we aren’t finished with the special barrels. Several of you have asked me to test the 1:12″ barrel with heavy pellets that are longer. I’ve decided to test it at 50 yards with the heaviest, longest pellets I can find. But besides that, I’ll also test the JSB Exact Jumbo RS pellet in the 1:22″ barrel at 50 yards. The RS is 0.002″ longer but nearly a full grain lighter than the Premiers that were used in the first test, so we may see an accuracy improvement over the 2+ inch groups the Premiers gave. Being lighter, the RS will travel a little faster, which means it will also spin faster, and that may help the accuracy. We won’t know until we try it.
This is good
I told you when I started the twist-rate test that we might find specific things to test in the future. These are those things, plus a few more. What a ripple effect this has had on all of my shooting!