Primer Cratering?

[powerspc]

There's 4 (four) hi-res pictures attached. The first two show Case #1 in which there appears to be some cratering but the primer itself feels flat/smooth to the touch. The next two pics show Case #2 which definitely looks like cratering and there is a distinct edge that you can feel. I'm trying to figure out if Case #1 is considered cratering or just a heavy firing pin strike?

 

[Supersubes]

Yes, that would be considered cratering. Don’t worry about it. Worry about the case head separation case #1 will have the next time you fire it.

May just be your bolt face finish, but to you always get ejector marks, regardless of pressure?

 

[Supersubes]

It could just be the lighting, but that looks like a case that’s about to go.

 

[FishDr]

I saw the same thing as suoersubes. Are these once fired? There appears to be two ejector marks on this particular case … one just left of the Lapua trademark, and one somewhat centered over the “3”. Although they look different size. Did you perhaps buy once fired brass from another rifle or fire it in different rifles?

 

[Supersubes]

I saw the same thing as suoersubes. Are these once fired? There appears to be two ejector marks on this particular case … one just left of the Lapua trademark, and one somewhat centered over the “3”. Although they look different size. Did you perhaps buy once fired brass from another rifle or fire it in different rifles?

The other mark you see is the cutout in the bolt face for the extractor. The shape looks very AXMC to me. But wait, he’s a lefty....

 

[powerspc]

It's brand new brass, never fired. The part circled above is a variation in the color of the brass from shiny to somewhat dull, it is uniform on every case. Yes, I looked at some other brass fired yesterday at lower charges and I can see the ejector mark on pretty much every case.

 

[powerspc]

Correction; that was a line, but it appeared to be just a scratch on the surface. I was able to wipe it smooth with just finger pressure.

 

[spife7980]

I bet its that its new brass that isnt tight in the chamber so when it gets fired it has a bit of a running start to slam back into the bolt face which is causing the ejector and extractor marks. How far forward did the shoulders blow from virgin brass?
That said.. they are still pretty hot loads to leave the marks.
If you are getting marks you are over pressure even if you arent catastrophically so yet.

 

[powerspc]

The shoulders measured virgin at 2.2695" and fired at 2.2735" (+.004"). I tend to be ultra conservative, if that's cratering (I think the consensus is definitely "yes") then I will be backing way down and crawling back up very slowly.

 

[spife7980]

Thats not much a an increase in shoulder position, Id back down. https://www.primalrights.com/library/articles/understanding-pressure

338 lapua, what bullet and powder? How far from the lands are you seated and whats your CBTO for touching the lands vs where they are seated?
Backing down 10% and working back up would be the safest method to find you max.

 

[powerspc]

Retumbo
Fed 215M Primers
27" Bartlein Barrel/1-9.5" Twist
Lapua 250 gr. FMJBT-Lock Base
CBTO: 2.9570" (I measured the lands at 2.9690", so I should be .012 off)
COL: 3.625"

I was working off the Hodgdon load data on their website, so I started at 90.0 grains and worked up from there. I didn't see any signs of over pressure until today at 95.0 grains (Hodgdon lists starting load at 90.0/max at 98.0) which was my Case #1, I shot 1 round at 95.5 grains which was my Case #2. It looked like there was a node (a flat spot) between 91.0 and 92.0 but I wanted to see if there was anything else of interest. at 91.0 I was averaging 2818 fps, at 92.0 2855 which now I'm thinking is probably pretty good.

 

[spife7980]

Hodgdon uses norma brass, youre using lapua. They are also seating a different bullet .075 deeper than you are.
I cant tell you the specific hardness and volume differences between the two.
But I can see that with the norma case hodgdon was getting 2853 at 98 grains. Youre getting those velocities with a much lower charge weight of 92gr in your lapua case.
Sounds to me like you found your max for a lapua case, maybe seating them a bit deeper will help a tad but if its shooting good at 91.5 then I would just call it good in the search for additional velocity via powder.

 

[powerspc]

Yup agree, I also appreciate the link from Primal Rights; I actually had it and it was one of the reasons I asked the question as they seem to draw a distinction between "cratering that is smooth to the touch" versus "cratering that has jagged edges". In any case, I think 91.5 is going to be the ticket (not a statistically significant sample size but I had an ES of 10 an SD of 3.91 at that charge). Thanks as always for all the input!

 

[Huskydriver]

That line around the case head is more than likely from sticking the case back into your ammo box primer side up. It taps back and forth in the square and puts a ring around the case. I get a ring like that around my larger brass if I leave it in my ammo box for awhile. I about freaked out thinking a ton of lapua brass was about to fall on the 3rd firing but as you saw it wipes off.

Your def on the upper end with retumbo and a 250 honestly. That's a tad above my Max with lapua brass as well.