Cratered primers

[RidgeRebel]

All of the loads that I shoot in my RRA Coyote have cratered primers even factory loads. Cause for concern? Also the brass comes out slightly sooty but I was told that was normal in AR's though. True or false. In an earlier post somebody mentioned that some times the action opens too soon on some AR's and causes the soot. How can I tell if that is the case with mine. The rifle seems to shoot well. Any suggestions would be highly appreciated.

P.S.
Thanks to all of you who share your experience with less experienced shooters like myself. This forum has been a wealth of information to me. Thanks a million.

 

[Jester8]

Re: Cratered primers

Taking a WAG here but maybe the firing pin hole is oversized causing the primer to flow in there and crater. My Win 70 always has cratered primers too, no matter what the load. Rem 700 never has.

 

[DMS]

Re: Cratered primers

Cratered primers is more often a sign of high pressures than a firing pin problem.
Some primers will show pressure more than others. One reason I recommend staying away from Winchester primers in the AR with heavy bullets (75 and up).
Cases being sooty is normal.
Were you shooting factory or reloads?

 

[RidgeRebel]

Re: Cratered primers

I have been shooting both factory ammunition and reloads and both had cratered primers. The reloads are 55 grn Hornaday soft point w/ H4895 and cci 400 primers. The factory rounds are 55 grn fmj PMC. My concern is causing damage to the firing pin?

 

[Winchester 69]

Re: Cratered primers

Cratering is not caused by high pressure or the firing pin. Cratering is caused by excessive space around the firing pin, and it leads to pierced primers which can cause damage . The solution is in bushing the bolt face to reduce the gap. The primer doesn't crater if the brass doesn't have a place to flow.

 

[sailhertoo]

Re: Cratered primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Winchester 69</div><div class="ubbcode-body">Cratering is not caused by high pressure or the firing pin. Cratering is caused by excessive space around the firing pin, and it leads to pierced primers which can cause damage . The solution is in bushing the bolt face to reduce the gap. The primer doesn't crater if the brass doesn't have a place to flow. </div></div>


....

 

[eddief]

Re: Cratered primers

On a bolt gun cratering can be caused by a enlarged firing pin hole which can show on soft loads also.

Plus it can be caused by a high pressure load which will push your firing pin and spring back allowing the flow of the primer. Bushing the bolt face and having the firing pin turned down will help.

Just be careful if you have it bushed and turned down, because if done right you will be hard pressed to see pressure signs from your primer again. So keep an eye out for signs...hard bolt lift, ejector marks and etc.

 

[DMS]

Re: Cratered primers

IMHO, CCI 400 isn't a good primer for .223. I would go to something with a harder/thicker cup. Rem 7 1/2, CCI BR4, or CCI 450. Also, knowing the tolerences AR bolts are held to I doubt that you will find a problem there. Could you post a picture? I am wondering if what you are calling cratering may be normal.

Here is a real good article you should check out:

http://www.radomski.us/njhp/cart_tech.htm

 

[DMS]

Re: Cratered primers

BTW, forgot to add: cratering won't hurt the firing pin, but a primer piercing will. The gas will erode the tip. Can also ruin the bolt if bad enough.

 

[DMS]

Re: Cratered primers

One other note about the article I linked above. That was done some years ago before Winchester changed their small rifle primer. They used to handle case pressure much better. I would not recommend it for most of the loads listed, or for any .23 loads for that matter.

 

[Larry Burchfield]

Re: Cratered primers

How clean is the chamber? Dirty guns will cause pressures to be high in an Auto.
larryj