Gunsmithing Pitting on bolt face around firing pin

[Swift]

Looks to be the same diameter as the primer so overpressure? The macro setting made it look a lot larger than it is but the real dark spots are where it's pitting' there's 3 of em. The rest is residue.

Is this an issue? The bolt and action(rem sa) are trued so I'd prefer to avoid replacing the bolt.

 

[buffybuster]

Re: Pitting on bolt face around firing pin

That's likely due to gas cutting from gas leaking past the primer. A small amount of marking/discoloration is not uncommon. Was there a time you were running brass with loose primer pockets or really pushing the loads?

If it's not getting worse, then it's pretty much cosmetic. If it gets worse, first find the cause and consider getting the FP bushed.

 

[Swift]

Re: Pitting on bolt face around firing pin

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: buffybuster</div><div class="ubbcode-body">That's likely due to gas cutting from gas leaking past the primer. A small amount of marking/discoloration is not uncommon. Was there a time you were running brass with loose primer pockets or really pushing the loads?

If it's not getting worse, then it's pretty much cosmetic. If it gets worse, first find the cause and consider getting the FP bushed. </div></div>

Highest charge it saw was 43gr H4130 pushing a 142smk. Switched to Lapua brass and had to back it off after getting some ejector marks with the initial 43gr charge. It's been eating a steady diet of 42.2gr since.

 

[Country]

Re: Pitting on bolt face around firing pin

Try harder primers and uniform the primer pockets to get them seating perfect.

 

[Raven 6]

Re: Pitting on bolt face around firing pin

I had the same problem once using Lapua brass and Winchester primers, they didn't like each other to well. Now use Federal GMM primers in Lapua brass and no problem. I have also used Winchester primers in other brass, no problem, but when I put the two together there wasn't a good fit.

 

[jiqwe]

Re: Pitting on bolt face around firing pin

The best plans do not survive first contact with the enemy.

 

[Agatha254]

Re: Pitting on bolt face around firing pin

Luck favoring the prepared. I'd rather be lucky than good any day.
The best plans do not survive first contact with the enemy.

 

[19Scout77]

Re: Pitting on bolt face around firing pin

What kind of priming tool are you using? I find it is better to use one that has some "feel" to it so you can tell if the primers go in too easy. If the resistance is light, the pocket is loose...so you should throw the brass away.

 

[Swift]

Re: Pitting on bolt face around firing pin

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 19Scout77</div><div class="ubbcode-body">What kind of priming tool are you using? I find it is better to use one that has some "feel" to it so you can tell if the primers go in too easy. If the resistance is light, the pocket is loose...so you should throw the brass away. </div></div>

That sounds like the issue. I use a Lee press to fit primers and noticed the primers sat unusually easy on about 1/3 of the cases. These were brand new Lapua cases. Guess I should give em a call. I've been using CCI 200 primers with all types of brass and all sorts of calibers without issue.

It's almost time to re up on components but now I need to reconsider. I had planned to switch from 4350 to RL17 but with FGMM primers and Lapua brass I'm concerned that's gonna run too hot.

 

[JByrd]

Re: Pitting on bolt face around firing pin

Def loose primerpockets

 

[19Scout77]

Re: Pitting on bolt face around firing pin

In addition to getting a hand held "feel" type priming tool, since the brass is new, before you scrap it, give wolf large rifle magnum primers a try. They are NOT a hot primer, but simply have a brass rather than a copper cup, so they are harder. They also have a slightly larger diameter than most other primers so they usually buy you a couple extra reloads after the pockets loosen up.

 

[Swift]

Re: Pitting on bolt face around firing pin

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 19Scout77</div><div class="ubbcode-body">In addition to getting a hand held "feel" type priming tool, since the brass is new, before you scrap it, give wolf large rifle magnum primers a try. They are NOT a hot primer, but simply have a brass rather than a copper cup, so they are harder. They also have a slightly larger diameter than most other primers so they usually buy you a couple extra reloads after the pockets loosen up. </div></div>

Great tidbit of info. I've yet to hear back from Lapua so that might be the ticket.

I'm kind of disappointed. $110 for 100 cases and 1/3 of em are outta spec. Not a good first experience with Lapua.