Picking a new M4 barrel...

[onearmedswordsman]

I can't speak about the tracers. Your experience differs from mine and from "conventional wisdom."

Exactly, which leads me to conclude that somehow my M4 bbl has a lot to do with it. Hence, the search for a replacement.

If I could have just one AR it would have a 1:9 twist and it isn't any surprise that it's the most common now in off the shelf guns.

What do you have now (bbl profile, lenz, twist)? No need to list all your 20-plus uppers/rifles , only a representative sample. Why? You've made me think hard about 55gr. I have only one AR platform rifle and I am not happy with it. If more are to come, I'd like to get on the right path now.

I started LR shooting with a 308Win bolt. Although 168SMK and 180gr Noslers do fine, I obtained best performance from 155gr silver scenars on a 1/11 24" bull bbl pushed at just under 2800 fps. There is something about driving that bullet as fast as possible to its target that seems to work wonders. I know this is different from the fast 55gr premise on the AR platform, but, this now is about external ballistics, not terminal ballistics.

The .224 bullet in 5.56 is known to have some unique tumbling and breaking characteristics upon impact which causes wound channels beyond what common wisdom would expect. Those events don't happen without speed and they happen more or better with the shorter bullets as in 55 and 62gr, which is what the military happens to use.

Stoner had it right the first time. When going fast, the bullets blow to smiterines. If too slow fragment, then, it'd tumble. IIRC when the military moved to from 1/12 to 1/9, 55gr ball lost most of latter wounding capability (55gr ball is not particularly unstable IMH, like when compared to 5.45x39 7N6). Terminal ballistics relied mostly on fragmentation, which diminishes after just over 100 yd. But, that's from the top of my head... memory could be failing me...

My best and favorite load out to 500 yds is a 55gr boat tail at 3150 fps, or about XM193.

What's your favorite 55gr HPBT bullet, that you handload for? Why?

 

[Gunner3456]

Exactly, which leads me to conclude that somehow my M4 bbl has a lot to do with it. Hence, the search for a replacement.

I wouldn't toss an otherwise good barrel. I'd also suspect the tracers.

What do you have now (bbl profile, lenz, twist)? No need to list all your 20-plus uppers/rifles , only a representative sample.

My most accurate AR 15 is, believe it or not, a Del-Ton with a 20 inch barrel and 1:9 twist. I don't know how many lands!

I can say that I "know" that the chrome moly barrels are quite a bit more accurate than the chrome lined ones. (mine.) I've also read that this is true.

Why? You've made me think hard about 55gr. I have only one AR platform rifle and I am not happy with it. If more are to come, I'd like to get on the right path now.

A shorter (and therefore lighter) bullet in any given caliber has two advantages.

First, it has a shorter lever arm for the back end to push against the front end. The front is experiencing atmospheric drag so the back is pushing, and wants to come around and pass the front! (Arrows have feathers to counter this but that's more complicated than that.)

Second, even though it's shot in a lower twist rate barrel, it is faster so it spins faster. It also contains less weight (inertia) to get spinning. A faster spin rate gives it greater gyroscopic inertia. Longer bullets are simply harder to stabilize, while our instincts would say the opposite is true.

I started LR shooting with a 308Win bolt. Although 168SMK and 180gr Noslers do fine, I obtained best performance from 155gr silver scenars on a 1/11 24" bull bbl pushed at just under 2800 fps. There is something about driving that bullet as fast as possible to its target that seems to work wonders.

See above.

I know this is different from the fast 55gr premise on the AR platform, but, this now is about external ballistics, not terminal ballistics.

Exactly.

Stoner had it right the first time. When going fast, the bullets blow to smiterines. If too slow fragment, then, it'd tumble. IIRC when the military moved to from 1/12 to 1/9, 55gr ball lost most of latter wounding capability (55gr ball is not particularly unstable IMH, like when compared to 5.45x39 7N6). Terminal ballistics relied mostly on fragmentation, which diminishes after just over 100 yd. But, that's from the top of my head... memory could be failing me...

Terminal ballistics aren't really the main issue with 55gr. Tumbling and breaking upon impact are. That causes the wound channel damage which exceeds anything you'd come up with on paper. The tumbling causes the bullet to change course in an animal body and also of course makes the bullet effectively larger than its actual diameter. It also causes it to rip and tear. If the bullet breaks there are also multiple wound channels and more chances of a vital hit.

What's your favorite 55gr HPBT bullet, that you handload for? Why?

I don't use the HP's. I use FMJ. I don't find increased accuracy (for my guns) with the HP although I know that "match" ammo is HP for accuracy, not damage.) The reports of wounding capability of the FMJ from breaking and tumbling upon impact are horrendous. I use any good name brand which is a better price at the time.

Disclaimer. All of what I'm posting is based on what I've read and what I've experienced with my guns in several calibers. YMMV and I may have inaccuracies in my recollections.