AR 15 Crimp Or Not?

newmexkid

New member
Getting closer on starting to load up some .223 brass. So, I come across some old posts on the Internet. Back then some guys were crimping others weren't. So now it's 2018 what are you guys doing, crimping or not? I will be using standard FL die.
 
you'll have to test and see which your rifle likes better honestly.


i do crimp, but only lightly - usually 1/4 turn or so from contact on the case mouth with Lee FCD's.

the one caliber i do have a very specific crimp for is my 450 bushmaster - i set my die to give me 0.475 at the case mouth help make for good consistent ignition as well as mitigating any potential bullet movement with those big fat projo's.

YMMV
 
I crimp all of my AR-15 ammo, except for P-Dog ammo. I have had bullet set back happen, especially on the 6.8s, used for deer hunting. And the 458 SOCOM, scares me at the thought of bullet set back. So I crimp.

The only ARs I don't crimp for are a 223 Wylde chamber, a 6mm WOA, and a 204 Ruger, that are used almost exclusively for P-dog shooting. There I can keep an eye on cartridges, and bucket anything that gets set back.

My accuracy tests of crimped versus not crimped shows no measurable difference. Well actually in the tests groups, for my LR308, the crimped rounds shot measurably tighter groups. That rifle has always been a bit different.
rolleyes.gif


Squeeze
 
Well, I see that the comments that have been shared read mostly the same as posts from years back. So, I think I will see how much pressure I feel during the bullet seating and go from there. Thanks guys.
 
If you are going to crimp, the Lee crimp die is very popular, easy to use and affordable.

If you are going to hike a bunch with bullets in the mag rattling around for hours and days you may consider putting a nice little light crimp on bullets with a cannelure. If your rifles cyclic rate is abnormally high it could help too.

Various makers of expander balls dimensions "could" vary a bit. If the ball was on the bigger side you may have a tiny bit less bullet tension. I suppose with an out of spec product you could get bullet set while the round is chambering.

I take my expander balls down a touch with a smooth stone and oil, then polish them with emery cloth. This takes a teeny, tiny bit of material away. If you push reasonably hard against your gun bench with a loaded round it should not move the bullet. It never hurts to measure a round and then chamber it to see if it sets back.

For the most part i don't crimp.

Some bench rester types i have met crimp. They have the mindset that the max pressure is right around the time the bullet releases into the lands. Some believe that a crimp really helps the uniformity of the process and therefor can bring your velocity spreads down a tad.

For me i do the velocity spread mitigations testing powder case fill, bullet seat depth, primer & powder combos.

Trimming the last few feet of extreme spread after that is outside of the scope of this married man with kids. I don't shoot long range and don't have so much time for the extreme details. Though i do know what they are.

Some very good shooters put a very light crimp on even match bullets. These very good shooters have great success. Over crimping will deform the bullet and be counter productive though.

Its a solitary sport that requires a lot of testing. These are very easy experiments.
 
Quote: If you push reasonably hard against your gun bench with a loaded round it should not move the bullet. It never hurts to measure a round and then chamber it to see if it sets back.

I shot a lot of 30-06 loaded for competition with the Garand for years and never crimped. Same for predator hunting with the AR until I wound up with an action full of powder one day due to a bullet pushed back into the case loading the rifle. This results from repeated loading and unloading the rifle stand after stand. I now crimp predator hunting ammo.

Regards,
hm
 
Originally Posted By: BrownieStill no crimp here. Thousands of rounds and no issues yet.

Yeah. Never a crimp. Never even tried a crimp to see what might happen.
 
I use the Lee factory crimp die for my 6.8 SPC for hunting, it just barely moves so I don't think it's really doing much. I've had to pull a couple bullets and it took a lot of hammering to get them out.
 
I have my expander ground down a bit and on some dies I don't even use it at all. I'll see how much force it takes to push a bullet into the case and I'll go from there.
 
Update. Today I loaded some rounds and my boy had turned my seating plug In the last time we reloaded. Luckily I checked the forst 2 rounds and caught it. Popped the rounds in my RCBS bullet pulling hammer and after 10 hard whacks with the hammer there was no movement of the bullet in the case. Tried the other round and same result. Nada zip zilch bullet didn't budge with no crimp.
 
Originally Posted By: SqueezeI crimp all of my AR-15 ammo, except for P-Dog ammo. I have had bullet set back happen, especially on the 6.8s, used for deer hunting. And the 458 SOCOM, scares me at the thought of bullet set back. So I crimp.

The only ARs I don't crimp for are a 223 Wylde chamber, a 6mm WOA, and a 204 Ruger, that are used almost exclusively for P-dog shooting. There I can keep an eye on cartridges, and bucket anything that gets set back.

My accuracy tests of crimped versus not crimped shows no measurable difference. Well actually in the tests groups, for my LR308, the crimped rounds shot measurably tighter groups. That rifle has always been a bit different.
rolleyes.gif


Squeeze



Squeese how do you keep an eye out for bullet set back with the
Ar loads that you don't crimp?


Do you drop the mag each time and look at the next round, or open
the bolt and look at the round that just chambered to see if the
feed ramp pushed the bullet back?

The AR cycles so fast it would be hard to check any other way, wouldn't it?
 
I am with the crimp squad. I also have had the action full of powder with a bullet pushed in the case, also after 7 or 10 blank stands.

I saw on another forum about an ar-15 blew up. The info fit my theory perfectly, if every thing went just wrong.

The bullet set back in the case upon loading, then it cocked slightly so when fired it jammed in the case neck which raised pressures to blowup levels.

I don't want to prove this at my house so I crimp.
 
Originally Posted By: who me
Squeese how do you keep an eye out for bullet set back with the
Ar loads that you don't crimp?


The short answer is I only find it, if I have to extract a live round. If I get set back on a round getting fired as soon as it is loaded, I have no way of knowing. I might suspect, if I find signs of pressure on a known load that typically isn't showing pressure, but it could be something other than set back, causing pressure spikes, too.

As others have mentioned, making sure one has good neck tension, is most important, if one doesn't crimp. For the rifles I mentioned, sub-MOA loads are required, so I do all of the obsessed with accuracy steps I can think of, including polishing neck sizing balls, for a bit more, and consistent, neck tensions. All of my periodic inspections of chambered, but unfired rounds, for these rifles show no set back. Occasionally, typically magazine related, I have a horrible miss feed, and in clearing the rifle, I find a round tip mutilated, and the bullet set back. This goes in bucket, for possible salvage or scrap.

Squeeze
 
Last edited:
Squeeze, Thanks for the response.

I don't crimp for bolt or AR. I
do try to pay attention when seating
bullets. If one seats to easy, I push
the tip against the bench to see if I
can push the bullet into the case.

I have missed finding a split neck, which
shows up when seating bullets.

One of these days, I might take the time to
chamber the same round a bunch of times to
see if I get any set back, or see if the bullet
slips out of the case any.

Thanks
 
No doubt the AR is a different bird compared to a bolt gun when reloading. The 17,20,22's have low mass projectiles, if you run .002-.004 neck tension and no lube bullet seating you shouldn't have any problems.
 
Crimping is one of "those" debatable issues that probably will never be put to rest. Without solid data, it more or less comes down to opinion, and most of us do not have the ability to get the kinds of data that would definitively prove or disprove the crimp debate. For everyone that crimps there is another guy that does not. We all have our reasons for and against. Try it with and without and see what the results are. You might see a change, you might not. This will tell you if you need to crimp or not.
 
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