At the range this last weekend I fired off 40 rounds of Q3131 Lot PL21 and had two rounds where the primer blew completely out of the case.   Thought this wasn't supposed to happen so easily with crimped primers?   Has anybody else been seeing this?

One of the primers blew while I was shooting over a chronograph, and there wasn't any abnormally high or low readings from it.  I probably never would have noticed the blown primer if I didn't happen to see a lone spent primer sitting on my bench.  They didn't create any feed problems.

Quoted: At the range this last weekend I fired off 40 rounds of Q3131 Lot PL21 and had two rounds where the primer blew completely out of the case.   Thought this wasn't supposed to happen so easily with crimped primers?   Has anybody else been seeing this?

Let me guess the box is 1999 production?

This was not uncommon with the 1999 production of Q3131 (USA produced ammo) - I've chronoed that ammo as being VERY VERY hot (as high as 100fps faster than the Military Specification).  Note Lot PL 31 is noted for running hot in the MD-AR15 Ammo FAQ and I'll bet the Ammo Oracle covers this issue as well.

They didn't create any feed problems.

Consider yourself lucky they can do all kinds of nasty things - from makeing the trigger feel bad, prevent the trigger from working at all, and worse case is locking up the rifle tighter than Ft Knox (I've had all 3 happen).

Quoted: Consider yourself lucky they can do all kinds of nasty things - from makeing the trigger feel bad, prevent the trigger from working at all, and worse case is locking up the rifle tighter than Ft Knox (I've had all 3 happen).

Yep.  Nothing ruins your day at the range faster than a primer jammed in between the bolt carrier and the inside of the upper receiver, especially when the bolt carrier is just far enough back that you can't get the upper off the lower.

A ittly bitty crimp ain't going to hold that primer in if the pressure gets too high.

Usually a bunch of gas and crap spews into the rifle, so cleaning it right away might be a good idea.  Some people put a bunch of grease in the lower to try and catch a primer before it locks up the trigger or something else.

To minimize risk of over pressure with ammo on the edge:

Don't get ammo hot by letting it sit in the sun.

Don't let a round sit in the chamber warming it up.

Do make sure you don't have a off center or out of spec chamber causing excessive pressure.

Do make sure there isn't any crap built up or foriegn material in the chamber, throat or riflings.

Sometimes not just the ammo puts you over the pressure edge, but a culmination of many things.

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