Pondering fast twist AR's

[Wayne S]

I'm just pondering and looking for thoughts on if you think a longer .225 bullet would help negate the effect of the fast twist. The point of the gas check being below the case neck come into play for some and if it effects accuracy. Just as BR shooters use the slowest twist that will stabilize their bullet to reduce any flaws in their bullets, could, longer bullets be used to reduce the effects of the flaws in cast bullets.

[Larry Gibson]

Wayne S

I prefer heavier cast bullets (60 - 70 gr) in 7 - 9" twist ARs simply because they build sufficient psi for reliable functioning at lower velocity than do lighter weight cast bullets. I am one who prefers to keep the GC (or at least the top of the GC) inside the case neck. Too long of a cast bullet in a fast twist can have negative impact on accuracy; the CM in the 65. Swede is an excellent example.

Larry Gibson

[freebullet]

Wayne
I don't yet know the answer. I will be testing those boolits you sent me in a 1/7 ar along with a couple other boolit designs. I will be sharing the results here when I finally get them loaded. Walleye's got in the way of my testing because they are biting and delicious.

[Screwbolts]

I tend to gravitate towards "heavy for caliber" cast boolits from previous experience. I'm not saying that accurate loads can't be found with "light for caliber" boolits, but it seems easier to find consistent accuracy with the heavies. In the case of the AR, you have the "gas operated" complication as well. Too light of charge, too fast burning powder, and no action function. Too slow powder and you have unburned powder in the chamber and action.

I purposely chose the NOE 225-70 over the longer, heavier ACE because of a maximum loaded round length and where it would put the GC, and the GC is still sightly below the neck with the NOE at 2.260" OAL (maximum that will fit in my magazines). If it were not for my fear of "riveting" from a more deeply seated boolit, I might try the ACE.


As you know I have the ACE Nato, yes I have to seat the check and first band below the neck. I have shot them with dacron and without, Gator checks and Aluminum check. I have also pushed them to 2450 from 20" 1x9 barrels. using Surplus RE15. I thinks with the slower powders there is less of a chance of riveting, I have not had any problems with them seated in the case.
I have also settled on 19 gr of RE15 as the great load for them, for my shooting. My Crony indicates 1920 FPS from 16" tubes and 2035 FPS from 20" tubes using my surplus RE15 @19gr. and readings at 15'. The Aluminum checks also are hitting the gongs at 100 yards. spattered flat checks lay on the earth under my gongs.

Your mileage may very, but as I have said this load works all my gas guns regardless of barrel length and carrier weight. and is a real pleasure to shoot.

Ken

[popper]

Fast twist is to stabilize heavier (thus longer or AP) boolits. It does put more stress on the boolits when engaging the rifling. Try an experiment - load as long as the chamber will allow, drop into the chamber (no mag) and try accuracy. Do the same with mag loaded rounds. Also try annealing the GCs. I'm finding (300BO - 165 RNFP WD seated in the neck sans check - ~1600 fps) the noses bend when loaded from the mag. You may have to adjust your load to slow the bolt down a tad.