Home Forums Hunting & Shooting AR and Tactical Rifles Crimp or not?

Picking up my first AR tomorrow. Got 500 new LC cases coming too.

Seems to be some difference of opinion on how necessary it is to crimp ammunition.

What say ye?

Thanks.

Never have and see no reason to start now.

I have no idea how many handloaded rounds I've put through AR's.

Ed

With sufficient neck tension, I've had no issues with uncrimped rounds.

I have far too much brass to keep it all separated closely by lot except for some small lots used in my more precision guns, therefore, there is always more variance in the neck springback / tension for all the rounds to have the same neck tension when the bullets are seated.

So, yes, I use a Lee Collet crimp die & very, very lightly squeeze the neck to, hopefully, a level that tends to somewhat uniform the grip on the bullet.

Hard & heavy crimps can cause other issues if overdone.

Ejecting a few unfired rounds occasionally & examining them for bullet setback from hitting the feedramps as the round is chambered might give a clue as to whether a crimp is needed or not.

MM

What Montana said. I put a very light taper crimp just to uniform neck tension and prevent any setback. Only takes a quick second to do and I don't have to worry about a loose one moving on me.

I read many articles and reviews before putting the Lee collet crimp behind the bullet seater on my press. The way the LCC works doesn't deform case necks unless you try very hard to. It may not be necessary but never found a test where it hurt either. It's one extra pull per cartridge is all.

It did nothing to hold in the Winchester 64 gr. PP's that I bought though. I kinda wanted those to work too.

I set all of my seating dies for a slight crimp, the AR is no different. This has been known to also help improve run-out and minimize TIR as well. Kind of like killing 2 or 3 birds with one stone, so to speak...

I never crimp rifle rounds, except for lever actions. I have the Lee FC die, so I guess I'll test my loads for good neck tension and crimp if needed.

One of the bullets I'm gonna try is one of the Barnes frangibles. I'm thinking too much crimp might not be a good thing with those.

Thanks, all.

not

Someday I'll work up the motivation to test a couple different loads crimped and uncrimped.....

I have and there did not appear to be a difference in groups.

I have with carefully prepared brass, same headstamp, same number of firings, trimmed and freshly annealed.
The uncrimped was more accurate, but not by a lot.

Ya gotta run the test at least 10 times, with 10 rounds/per, in order to be meaningful as one test don't mean jack schitt.................just sayin'

Seriously, I think it matters a lot as to how hard they are (over) crimped.............but if you are going to crimp, it does have to be enough to get uniformity.

MM

My main interest in this is whoopsie avoidance. Not expecting accuracy miracles from a 16" carbine, just good function.

have one AR rifle........Aero Precision 300 BLK.........

yes I crimp..........what does it hurt ?

Lee FCD..........nuf said......

The 5th station of both of my progressives sport a Lee crimp die.

Why not crimp if its a free motion as it is in a progressive

I'll bet I've shot 75+ K rounds in competition that I loaded, out of a match AR in 223 and never crimped the first one. Never had my gun have a FTF or failure to fire due to a round that tied the gun up due to bullet creep... Waste of time in my opinion...

There is a whole lot of ink on the affects on accuracy using the Lee FCD. Hard to find much negative.


http://www.accuratereloading.com/crimping.html

IF, there's any pushing the bullet deeper into the case as the round is pushed into the chamber, there will be more negative effect on accuracy than the potential loss of accuracy due to using a light crimp.

And unless you eject enough live rounds that have been chambered from the mag to know, then you really just don't know.

JMHO, YMMV

MM

+1 for the Lee crimp die. Run it on all ammo I build up that will be cycled in my ARs.

Crimp with the Lee crimp die...

A 16" AR carbine can be a lot more accurate than you might think. Obviously it depends a lot on the barrel and ammo, but below 1/2 moa is a reasonable expectation with the right load. At that level, crimping may or may not affect accuracy, you'll have to try it, although it's telling that most precision shooters do not crimp.

As to whether you need it or not - it's belt and suspenders, up to you to make that call. Neck tension alone should be plenty to resist bullet setback, and always has been for me, but if you've got something not right in the load process, like an expander ball that's too large, crimping might save you. Personally I don't bother, other than to just remove the flare when loading cast bullets.

Yes, crimp with the Lee Factory Crimp die.

I know when I tried to load the Winchester 64 PP and saw how easily they were moving I adjusted the Lee FCD to a pretty darn heavy squeeze and got them to hold. I was still scared of pushing a bullet in and creating a big pressure spike cause I always seat a mag and release the bolt to load. I checked the first 2 rounds I put into battery and found they were pushed back.

I'm not saying that happens to properly sized bullets that are being held by properly sized case necks, I can't, but I do think there are forces that could affect seating depth when the bolt moves forward into battery. Like MM said , you would have to eject and caliper a bunch of them to find out.

I think I could do that with ammo made up with no primer or powder. Without the minuscule chance of a slam fire I could test this at home. That would tell me about my sizing mandrel.. and the bullets I use.. in that one gun..you'all are on your own.

You can also measure the ID of the case necks & the OD of the bullets being used to see how much interference fit you are getting.................nominally, .002-.003" is typical & works fine, depending of course, on the hardness of the particular brass.

MM

There ya go... we loaded up to 20K a year for Carolyn and I and a couple of juniors here and there... from about 89 till 2004.... thats a few rounds.

I don't even know if I have a crimp die for a 223.... full case of powder, control neck tension with a collet the right size.

The only case that I ever needed to crimp was lead bullets in my .454 Casull. Walking bullets will lock up a cylinder in a hurry. There was a newspaper guy here who had that happened when he was trying to fire the second shot at the bear.

Jeff, It's Whiskey Tango Foxtrot, over..

edit on the way. LOL

They get pissed around here on the fire radio if you talk about over or roger... or God forbid Niner....

I use a Lee FC die.

What the foxtrot? I learned all my radio protocol in the Artillery, over.

You might know what "Fire for effect" means, then. (grin)

This ^^
If I buy ammo that is not crimped and it's destined for a semi auto, I crimp it.

kwg

yep, sure thats why all the winning AR shooters in highpower/service rifle crimp all their ammo all the time, it helps groups and reliability.... LOL Then again the way most shoot an AR it sure won't hurt the accuracy....

Never mind the fact that I know more than a few with at least half a million uncrimped rounds in the AR with never a crimp related issue... but then we do tend to use 100 percent fill and control neck tension the better way, via bushing rather than crimp.

I don't trim AR brass so this method won't do me much good