New 6.5 Creedmoor build---question about primers

[jonny rotton]

i just built a super light weight 6.5 (creedmore). i am still waiting on my new jp super bolt and light weight carrier. so i put in a temp from a 308 i i test fired three rounds. the indent in the primers stick up just a little bit. whats the issue??? any help would be appreciated. i already had a bussel of grendels. lol

[FLshooter]

[jonny rotton]

no, i was shooting factory ammo. where the firing pin hits the primer there is some primer metal sticking up. i am thinking it may be the headspace but i really dont know. it is not the bolt i will be using. it may be in this week. i hope.

[FLshooter]

[Lemonaid]

Post a pic for better info on the reply. That said, sounds like primer cratering. Could be over pressure, could be under pressure could be firing pin or the firing pin hole in the bolt. Could also look different with a different primer as some are harder/thicker than others.

[jonny rotton]

WIN_20200322_18_14_42_Pro.jpg this is my first attempt at posting a picture

[jonny rotton]

WIN_20200322_18_20_30_Pro.jpg second try

[Lemonaid]

Looks like over pressure. Primer has completely flattened. Just my opinion, others may have more help.

[jonny rotton]

i've never seen this before. the indent is cratered. it is a temp bolt and carrier. my real one hopefully comes in this week

[FLshooter]

[jonny rotton]

thank you for your replies. i hope it goes away when i get my jp bolt and low mass carrier.

[A5BLASTER]

And that is why the 6.5 creedmoor bolt use's a smaller fireing pin hole.

What your seeing is primer flow into the fireing pin hole of the bolt.

[jonny rotton]

wow thank you!!

[Klem]

A5 has hit the nail on the head.

It's primer flow or cratering caused by lack of support around the pin. Basically the firing pin hole is too big for the pin. Flow happen with normal loads as well as hot. The next severe step is that small circle donuts start breaking off the primers and get in everywhere to jam the action.

A thicker, stronger primer will mitigate this. A tighter hole with better tolerances from a quality manufacturer will solve it.

[lazyengineer]

A5 has hit the nail on the head.

It's primer flow or cratering caused by lack of support around the pin. Basically the firing pin hole is too big for the pin. Flow happen with normal loads as well as hot. The next severe step is that small circle donuts start breaking off the primers and get in everywhere to jam the action.

A thicker, stronger primer will mitigate this. A tighter hole with better tolerances from a quality manufacturer will solve it.

This. I have been dogged by this with my 6.5 CM, with a batch of ammo using soft primers, where it would blow a punch of the primer brass back into the firing pin channel, and cause all kinds of problems. FWIW, they were S&B primers, and I no longer use S&B primers for 6.5 CM loads; as they are just too soft for the high pressures of 6.5 CM. And yet, they aren't strong enough for a small-firing pin indentation, and will pierce. Work fine in a lower pressure round with a fat round firing pin tip like an M1 Garand or 1903, but for a modern 6.5 CM, I can't make them work.

Though, I will say, I do have S&B factory ammo, and in my guns that seems to work OK, just the independent S&B primers in reloads are doing it to me.