Is setback a potential issue with 5.56

[Significent]

I've just purchased a stripped AR15 lower and ordered a rifle kit. I'm gearing up to reload for it and wondering if a cannelure is necessary. For obvious reasons, I've only had to use taper crimps with my .223 bolt gun. However, given the force with which the AR15 round is slammed into the chamber, will setback be an issue if I were to use a taper crimp?

If setback is a potential issue, what's a good powder that would completely fill the case, mitigate the setback issue and result in accurate, standard-velocity rounds.

Thanks for your help!

[IllinoisCoyoteHunter]

Use a crimp and you won't have to worry about setback at all. Use a bullet with a cannelure to achive the best crimp. As far as powder, I have had excellent results with Varget. Others will show up here and say you don't need to crimp....but I do for piece of mind.

[kraigwy]

I've loaded un-told thousands of rounds for the AR since I got my first one in the late 70s. Most of compitition shooting. I have never had to crimp any of them.

The exception is, in the late 70s-early 80s I was selling remanufactored ammo to differant PDs and Gun Shops. Dies do wear out. I eleiminated this problem by getting a carbide die from HOLLYWOOD. I'm still using that die and still dont crimp bullets.

If you have a good sizing die, you want have to worry about bullets moving during recoil.

[amamnn]

I've had the same experience as Kraig. Any standard FL sizing die should do the job for you.

[Significent]

I appreciate everyone's input. I'll measure, chamber, and eject a few to make sure my dies are doing the job.

[markr]

That's a good idea. You can use the Lee Factory Crimp Die on bullets with without a canelure.

[totalloser]

Page 56 Lee Modern Reloading states crimp "required" for autoloaders, tube fed, and hunting ammunition.

Page 79 Speer no13 manual says the same, but says "recommended".

I crimp all my rifle rounds, and found small improvements in accuracy in my semiautos.

[James R. Burke]

I probably would crimp for the AR, or load a mag up umcrimped and take some measurements from the last few. I dont crimp any of my loads even the ones for hunting. But I do not use any autoloaders, and been lucky I guess with the magizine fit. I have a few Ruger No 1's being they are single shot hand fed you would be wasting your time crimping them.

[cornbush]

+1 on the factory crimp die, never had a setback, but I like the consistency it give on the pressures, they all start out with the same amount of neck tension.

[wncchester]

"Page 56 Lee Modern Reloading states crimp "required" for autoloaders, tube fed, and hunting ammunition.

Page 79 Speer no13 manual says the same, but says "recommended"."

Both of those are "rule of thumb" observations, no .223 peep-squeek recoil will set any bullets back so the "rule" won't apply.

[RoyalsSpeedShop]

I have not been crimping for my AR15 reloads and have had great results. The expander ball on my RCBS dies opens the mouth to .221 and the bullet is
.224. That creates a pretty tight fit without a crimp. I also found that the fine line between crimping and case shoulder crushing was ridiculously close. If I could find a Lee collet crimping die in stock I would buy one though.

[steve4102]

If you have a good sizing die, you want have to worry about bullets moving during recoil.

Recoil is not the issue. The cycling of the action, bullet slamming into the chamber with an abrupt stop is.

From Sierra Exterior Ballistics.

There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well.

To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension.

[wncchester]

??

[totalloser]

Plenty of folks do and don't crimp, I was just noting what the books say. Recommendations from the loading books tends to lean me towards crimping not so much for the risk of the bullet moving forward, but from it hitting the feed ramp funny and setting BACK creating an overpressure condition. Or from dropping one at the range, or in the dark (hunting/sd).

Personally, I really like the Lee Factory Crimp die. The crimp feature in the seating die is really reliant on the trim length, so if your brass varies, it fouls things up. The Lee FCD is nearly immune from length issues as it is a collet operated device.

I've read many accounts of how/why the crimp aids accuracy in certain instances (such as mine), and I *think* it basically is a benefit in conditions where inconsistency in case size/charge weight cost accuracy. The crimp holds the projectile back just a little while pressure builds, and keeps a little excess tension on it to guide it squarely onto the rifling. My suspicion (and many others with more experience) is that in instances where these inconsistencies are not an issue, the crimp is marginalized, and perhaps even detrimental to accuracy.

As to using a slower burning powder to support the bullet, I don't know. But I know bl-c(2) and win748 come close, but don't compress my 62 and 55 grain loads. www.pat'sreloading.com has wc846 (similar to bl-c(2)) for sooper dooper cheap ($95 per 8 pounder) and it meters really well and has made me happy accuracy wise. But I'm not as picky as some.

The idea of counting on the powder to support the projectile kind of worries me, as a compressed load from a bullet setback can bump pressures up alarmingly. However, there are a handful of loads in my Lee data that have the little "c" denoting a compressed load, so obviously in some instances it is OK.

[bullspotter]

I use 4895 powders, IMR and Hodg..... They are definatly compressed. I crimp all my AR 223 ammo and dont crimp my bolt gun ammo. I wouldnt look for a powder full case to keep a bullet from setting back, The bolt on an AR comes forward with pretty good force, and im thinking it would still set back compressing powder eevn more. To find out how hard the bolt slams closed, lock the bolt back, stick your pinky in the chamber and hit the bolt release.....LOL

[Powderman]

YES!!!!!

I have had significant problems with setback in the .223/5.56 cartridge, as fired from AR series rifles.

Most of those problems are experienced with 62 grain or heavier/longer bullets. If I do not crimp, the bullet is set back into the case. The result upon firing is that the bolt locks up and has to be pounded open. On the occasions that it has happened to me, I have seen blown primers, elongated primer pockets, ironed out headstamps, ejector marks, and when I do get the case out, it looks like a belted magnum case. Tain't pretty.

The solution? Crimp all cartridges intended for the AR series--or any semiauto--with the Lee Factory Crimp Die. You don't have to squeeze it like a lemon--just a medium crimp where you can see a light impression of the collet is good.

With this crimp method, I have used the 62 grain milsurp bullets with great success. Accuracy is MOA or better at 100 yards, both with my Armalite full sized and my Colt 6920.

[Alleykat]

The OP definitely didn't need to be crimping his .223 reloads for his bolt gun! I stopped crimping for my ARs some time ago. So far, so good.

[30Cal]

If you find your bullets moving more than about 0.005" when chambering, then you need to get your resizing die fixed (oversized expander ball). You should have more than adequate neck tension without crimping.

[steve4102]

You should have more than adequate neck tension without crimping

How much neck tension would that be? I have run several tests with auto loaders and I can tell you for a fact that neck tension as much as .006 will not hold the bullet in place during the cycling of the action. I have tested this with a Ruger Mini-30, Browning BAR and Colt AR-15.

If you want the bullet to stay put use the Lee Factory Crimp Die. Neck tension alone will NOT do the job.