Random pressure signs

[ZSteinle]

I have a 7 max built on a defiance anti, proof carbon that will show random pressure signs (heavy bolt lift and ejector mark). I will shoot a couple and they show no pressure at all then shoot another that is the same exact load that shows pressure. It will go back and forth from pressure to no pressure signs. Shots that show pressure are no faster than those that don't show pressure. ES is around 15 fps. About 80 rounds down the tube. About the only thing I can think might be happening is my fire form loads weren't hot enough to fully form brass and some got fully formed and some didn't. My fire form load was shooting 160 grain bullets at 2350 fps. Gun shoots 1/2" with a combination of rounds that show pressure and ones that don't. My load is adg brass, 162 eldx, 63 grain of h4831sc with a speed of 2930 fps. Any ideas?

 

[GLTaylor]

Probably a good assumption. ADG brass is tough. It may take 2 firings to get consistent brass.
Easy test is drop back 1/2 to 1 grain and fire. If intermittent pressure signs go away, there is your answer

 

[QuietTexan]

Max is an improved SAUM case right? I agree with 2x firings to fill out, especially on cases that are improved - one to blow out the case and suck the neck back, second to really fill out the chamber.

Sometimes it can take 3-5 firings before the shoulders really grow and bump consistently - the loads will shoot really well during this time but fired cases rechamber easily still. It's how you get good brass life - don't beat on the cases and don't oversize.

 

[RegionRat]

Can you spot the case dimension causing the issues?
Is there a case volume difference between those two steps?

If the problems don't go away soon, I would suggest a chamber casting to see if your sizing die, chamber, and brass are coordinated.

 

[tim_w]

Are you sure you got any and all case lube off all the cases?

That can cause ejector marks.

What primers are you using and how do they look on the case's with heavy bolt lift.

Check the h2o volume between them.

What is the jump for this load?

Maybe check BTO is consistent.

When you worked up the load how close were you to the load that showed pressure?

 

[djacobs629]

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