Crimping ?

do I need to crimp when reloading for my AR in 5.56?

Elkeater said:

do I need to crimp when reloading for my AR in 5.56?

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Maybe, what are you looking to accomplish? High volume plinking or low volume predator hunting. Most guys I know just run .003-.005 neck tension and that is more than enough. I actually crimp all of my AR stuff from 55 fmj to 77 RDFs but it is a very very light crimp. I found with 8208 and a little crimp I get really good ES and accuracy.

Maybe crimp just enough to roll the lip over for better feeding and holding the bullets in place during recoil. That's what I do for my .357 Mags and .44 Mags.

The main reason to crimp is to eliminate bullet setback. Setback can cause an increase in pressure to the point of being dangerous. Scott is correct in the fact that with good neck tension on the bullet you don't need to crimp. Myself, I only crimp bullets with a cannelure, using the Lee Factory Crimp die(the ammunition companies crimp with a collet just like the Lee die). The cannalured bullets I use are the 55 & 62gr fmjbt, and I use those mostly for plinking. When loading for CMP or competition I use the Redding full length Type S bushing die and I use the bushing that gives me proper neck tension to securely hold the bullet. I use match bullets without a cannelure and apply a light taper crimp. Between the neck tension and light taper crimp, I eliminate bullet setback without the possibility of deforming the match bullets and this ensures match grade accuracy. I only recommend using the Lee factory crimp die on cannalured bullets as it squeezes the neck into the bullet, and if set wrong ir can actually deform a bullet.

Satterlee Scott said:

Maybe, what are you looking to accomplish? High volume plinking or low volume predator hunting. Most guys I know just run .003-.005 neck tension and that is more than enough. I actually crimp all of my AR stuff from 55 fmj to 77 RDFs but it is a very very light crimp. I found with 8208 and a little crimp I get really good ES and accuracy.

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I'm a low volume predator shooter or slow fire precision shots at the range. Rarely do I shoot more than a 5 round mag and when I do high volume shooting I just buy bulk ammo since with my single stage press reloading more than 50 rounds becomes a chore.

Looks like I'll start with a light crimp just for feeding reliability.

Elkeater said:

I'm a low volume predator shooter or slow fire precision shots at the range. Rarely do I shoot more than a 5 round mag and when I do high volume shooting I just buy bulk ammo since with my single stage press reloading more than 50 rounds becomes a chore.

Looks like I'll start with a light crimp just for feeding reliability.

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I use the same crimp die Toddxusmc lee collet.

I use the Lee Factory Crimp Die on all my AR ammo. I use what I call a medium crimp. I set the die up until when I raise the ram the crimping fingers only go about half way between fully closed and wide open without a round in the die. I have experimented and I get better accuracy doing this plus makes me feel better about not having a bullet being driven back into the case during feeding. I use the crimp on all bullets and most don't have a cannalure.

Lee factory crimp die. If you set it up right you won't have any problems crimping any bullet. Even use it on some of my bolt guns.

I had thought about crimping when I made my 35 Whelen AI, but decided it was too much of a hassle. If the case lengths are not the same, then you will have uneven crimping pressure from case to case. Thus your chamber pressure will also change. If you crimp with a seating die, then the crimping process starts before the bullet is completely seated and you're damaging the bullet. So then you have to get a seating die and add one more step to your loading routine. I have never had a problem with the Whelen, nor my 375 H&H.

Since you are shooting an AR, the greater problem is the bullet moving forward as it is slammed into the chamber. Again, I have not had any problems with my ARs, including my Grendel and 7mm Valkyrie where I turn the necks lighlty to remove any high spots.

It's not an issue if you trim the brass

Only problem you may have crimping with Lee Factory Crimp Die is if you trim your cases too short or even trimming them to the suggested trim length can cause you to only get about half of the case with the crimp. I trim my cases 5 thousands longer than the trim to length and this give plenty enough case to get a good crimp on.

Not as critical with the lee factory crimp die.

I don't crimp for my purposes it's just and additional step I'm not in need of maybe if I was hunting dangerous game or something mission critical but I'm just s plinker.

I load 77 grain TMKs. I put a slight crimp on them, just enough to keep them from moving when the bolt slams them in the chamber. What I did was make a dummy round, put a slight crimp in it, put it in the magazine, then release the bolt catch so it chambers under the full force of the buffer spring, and eject the round. If my measurements show any change in COAL then I increase the crimp. Once the crimp is good then I leave the die set. So far I have an ES of 10 FPS with 24.8 grains of Ramshot TAC.