I've read all kinds of threads, some say absolutely, some say absolutely not necessary. I've reloaded for my bolt action rifles for years without crimping but this is the first time I'll try reloading for my AR. Do I need to worry about the bullets getting set back when they are chambering? I purchased the RCBS small base die set, not the one specific to ARs.
Thanks,
Shay

I crimp mine, but not very heavily.

Are you loading bullets with a cannelure? Mine don't have cannelures. I've got some 50gr vmax and 60 gr partitions.

Not necessary. I tried the Lee FCD to see if it did anything to enhance accuracy and I saw no effect whatsoever, good or bad.

Never!

I started to. Google AR-15 Kaboom.

If you think about how a semi auto works, it pulls back the bolt for you, then slams it forward under spring tension picking up a round from the mag to ram them into the feed ramps then into the chamber.

You don't get to "feel" what happens like you would in a bolt action weapon. When you work a bolt, it doesn't really ram the round into the feed ramps. It just guides things in so you can have a pretty loose bullet and not get set back.

When reloading mass amounts of ammo there is always a chance that 1 of your 1000 may have weak neck tension. During the firing process, when that weak neck tension round is thrown into the "guides or feed ramps" whether they be M4 cut or Rifle cut it will push the bullet back into the case if there is not enough neck tension.

This bullet setback will develop an extremely high pressure situation. I've warned people of it before and I go mostly unheard or ignored.

I can almost promise you most AR-15 Kabooms are caused by bullet set back. It's damn hard to do a double charge a .223...it may be done with some powders but not your common ones like H335 and TAC.

Now most AR-15 rounds have a cannelure, and you can crimp those. Many match rounds and high dollar rounds do not have a cannelure and should not be crimped because you will ruin the BC of those. You should check the neck tension on them before running them through a semi auto weapon.


Pick up some XM193 or some M885 ball ammo. Those are all crimped. The military specs say crimp the rounds. I load my rounds to 5.56 pressures, so if I got a Kaboom it would be a good one. It is of my opinion that I crimp my rounds because I do not want a bullet setback situation. Even though I have reloaded and fired 1000's of rounds of hand loaded .223 and my neck tension has always been enough, It only takes one bad round so this is a recent event for me because there have been a large number of Kabooms lately and I do not want to join them.

One should always check neck tension by trying to push the bullet back into the case on any new loads anyhow.

In the end....It's up to you. The cost of a Lee Factory crimp die is much cheaper than a new AR and any wounds you may sustain.

I say crimp them.

To answer your question, "is it necessary?"...

The answer is, no, it is not necessary.

As long as you have adequate neck tension, you shouldn't need to crimp them. I like .004"-.005" or more.

Neck tension and selecting a powder that results in a light compressed load is what I do. That is part of the reason i use varget for those loads.

I never have.

I have started to use a light crimp on my loads. I use to have rounds that the bullets keep getting pushed back into the casing when loading them into a magazine. Spills the powder everywhere of course. My COL is right as my books say to, I guess my resizer is not sizing right

every round I reload I crimp with a LEE FCD. real light crimp but I have no issues with bullets moving anymore. If you can get neck tensions right you shouldn't have to I guess but I'm not that smart. Excellent results so it can't be hurting me.

I realize this is not the same but I reload for my mini. I use varget, it is a compressed load. I do not crimp.

One thing to be aware of when counting on a compressed load to keep your bullet from seating back. When using an AR you can also have the bullet pull out when it chambers. This can be very important when using light (short) bullets and long throats (5.56 chamber) Just like an inertial(sp) bullet puller.

good tips

My necks are tight using RCBS .223 dies (if it's not a boat tail bullet, I need to expand the tips, then light taper), I also used Varget which ends up with a compressed load. So no crimp for me.

I do not

The AR-series die set is just a RCBS marketing ploy for their small base die, but adds a taper crimp seater (which is more applicable to many bullets). The SB die is rarely (never?) necessary, unless you have a really bad batch of once-fired brass of unknown origin. Just works the brass a bit more.

I have never crimped a single round loaded for my AR's, which includes mucho used in Highpower competition. Nor do I know of anyone else that does. But can't deny bullet setback is a very remote possibility. I'd rather smooth the feed ramps, to ensure easy feeding.

That's something to think about. I think I'll run a little experiment to see if this happens on my AR loads and if it is, I will go ahead and use my FCD.

Yes on 5.56, 300 Blackout and 7.62x39 in AR platform.

If you have shot one of the 30 cal ARs, you know how they jam the ammo into the breech without mercy.

Thanks for all the inputs guys. I wound up buying the RCBS set with the taper crimp die. I wasn't terribly clear in my first post - I'm loading for a 223/556 AR (Rock River). None of the bullets I'm planning to load have a cannelure. I plan to use a light taper crimp and make sure the bullets stay in place when feeding.

Now I've got a different issue. Where to find brass for a decent price. Seems everyone is sold out. I've got a bunch of Lake City brass but don't want to deal with the crimped primers.

Anyway - thanks again for the suggestions.
Shay

Scharch/Top Brass is usually a good source and price.

http://www.topbrass-inc.com/reloading-supplies/

Yes I crimp

Last time I checked, Berry's had new unfired LC brass.

I use the collet crimp from Lee. Just a light squeeze on the neck and the bullets dont move. I had an issue with a rifle without M4 feed ramps on Win soft points and this solved it.
Recently I bought some Lake City new brass and DID NOT have to resize it. Fit the guage and chambered perfectly. Set the press up and noticed the crimp die was not doing anything. Bullets were firmly held. Makes we wonder if the expander die is expanding the necks a little more than necessary.

BTW, Dillon primer pocket swage. Awesome investment. I did 2000 pieces in front of the TV over 2 short evenings.

Never.