6BR load too hot?

[infantrytrophy]

Is this 6BR load too hot? I just fired my first 2 rounds for barrel break-in. It looks like the primers are cratered slightly but the edges of the primer are still rounded. The picture shows 2 fired rounds, 1 unfired round.
Edited to add: The bolt lift is easy.

Load: Bullet SMK 95, 30.0 gr RL-15, new Lapua brass, bullet seated .020 off lands, primer CCI BR4.

Rifle: 6BR tube gun with Eliseo stock kit, Pierce action, 28' barrel.

 

[tiny68]

I see a lot of cratering with BR-4 in my factory rifles. It my guns I have exceed 30 gr of RL-15 with both 105 Berger VLDs and 107 SMK. The primer is not flowing around the edges of the primer pocket. If the bolt lift is fine I would see your good to go a little more powder.

Tiny

 

[jb1000br]

Use cci 450's and I bet the craters go away. Your load should not be too hot given the charge and bullet.

JB

 

[infantrytrophy]

Use cci 450's and I bet the craters go away. Your load should not be too hot given the charge and bullet.

JB

Thanks for the suggestion. I will try this, but it would be nice to understand why. Have you tested the CCI 450's vs. the BR4's with the same load? The primer cup thickness is the same for both primers. Here is a link to an article that documents this:
Primers and Pressure article

Randy Sikes

 

[HPMike800]

I have the same gun with a R700 bushed firring pin action and a Krieger 1:8 twist. I run 95 SMK's with 29.5 of Varget in rapids and 30.5gr Varget for 'full' load,2950fps). It's still not maxed at that. I shot a little RL-15 out of the gun at first and your load should be fine. I don't see any pressure. How was the bolt lift? Have you crono'd the load? From what I see, the firing pin hole is a little big, I heard 6BR likes to crater. I would think a Pierce action would have a tight clearance pin / hole.

I've had RL-15 temp problems in the past and left that powder behind. I don't think that's the current problem, bum a cup of Varget and try my loads above and crono them. Don't let the primers Perice. If the numbers look good and the groups are OK and the only pressure sign is cratering then fix the bolt.,the 29.5gr load is not a great grouper)

Your going to want to shoot 105/107's at 600.

 

[BoydAllen]

What you are seeing is probably caused by excessive clearance around the firing pin tip. Another contributing factor might be a weak firing pin spring. Greg Tannel of GreTan Rifles http://www.gretanrifles.com/
Does and excellent job of bushing firing pin holes, and his price and turn around are the best. I have sent more than one friend to him, an they are all satisfied with his work.

 

[gambleone]

I had same problem, like Boyd said, excessive clearance around firing pin. Sent it to Greg Tannel & problem solved. I then could go up a little more on the load without cratering & no pressure sign. Also I use 450 primers & either RL-15 or Varg.

 

[niceone]

every guns different i know but i shot up to 31.7 rl 15 with cci 450 today no probs with bolt lift but starting to show extractor marks at 31.7.......... 31.5 shot same hole so did 29.5 so i don't know what to do

 

[flatlander]

I've also got a Pierce action in my R5 tubegun in 6BR, and have been seeing cratering with R 7-1/2, F205M, & Wolf SRM primers since I started load development. Bolt lift is fine, and I'm thinking that indeed, the clearance between firing pin & FP hole in boltface is excessive. I don't have a pin gage set to measure the boltface FP hole dia. accurately, but see no other reason for the cratering I've experienced.

I won't build a BR or Dasher on any factory action without bushing the boltface, but didn't expect that a custom action would require it. However, my bolt's going out to Gre Tan to be bushed as soon as possible.

 

[PaperSniper999]

............ The primer is not flowing around the edges of the primer pocket. If the bolt lift is fine I would see your good to go a little more powder.

Tiny

Ditto. I also don't really see much I'd call cratering on his photo, but maybe it's just my old eyes..........<G>