Pierced Primers ???

[LitLBoy]

.20 Practical - Fed 205M - 26 gr. 8208 - 39 gr. SBK - LC 2011 brass. Some of the primers pierce, some don't, No pressure signs at all, all primers are from same lot, might pierce 4-5 in a row and then go 20 rds. no problem. Primers that pierce, a small disk size of firing pin hole is removed from the primer and found in the action. Brass is all match prep. I've loaded for 40 yrs. but have no experience with pierced primers. Any help really appreciated.

 

[Joe O]

I would switch to a harder primer cup,like Rem 71/2s.

 

[243winxb]

I just cut and pasted the whole thing-some may not appy to your firearm.

Pierced or Blanked Primers.

--------------------------------------------------------------------------------

1. Check the firing pin, it should have no gas cutting or deformities. 2. Firing pin protrusion should be checked. Internet search shows .055" to be about right for an AR15. Check with a gun smith as each firearm IS different. 3.The firing pin must stay in contact with the primer on firing. A weak hammer spring on an AR or a weak firing pin spring like on a Rem 700 bolt action will let the firing pin rebound on primer piercing when the hot gas pushes the pin backwards. 4.If the hole the pin sits in is to larger in diameter, the primer flowes back into this hole till the center of the primer separates and fall into the action or travels into the firing pin area. Bushing the firing pin hole will fix this. Or you may want to try a magnum primer with a thicker cup. Military ammo may have a crimp that needs to be removed before seating a new primer. The crimp is removed by reaming or swaging the primer pocket. Swaging may be needed here so the prime can be seated lower in the pocket. High primer = misfires & pierced primers. There is also a high pressure sign visible. The reloader was using a "starting" load and CCI 400 primers. The CCI 400 is thin & soft, change to a mag. or Rem. 7 1/2 primers. The pressure sign may have formed on firing the factory ammo. I just shot some XM193F factory, the web area expanded .0015" on firing. This is a sigh of a "hot" load.

 

[bigedp51]

The red highlighted area was done for the benefit of long headspaced milsurp rifles and may not apply here. Is your brass brand new? You may have too much head clearance.

 

[LitLBoy]

Thanks for the input guys!!