I have a rifle I bought at a gun show...
338-06 on a Belgian Mauser with a bolt stamped 1920...
The barrell has "Shaw" stamped on the bottom...
The wood stock was burned "tiger striped" with sand glued in the handhold spots...
The bore is beutiful!
The (Timney) trigger is excellent!

This rifle was quite obviously re-barrelled before the cartridge was standardized, so I'm clearly in the wildcat zone here.

The problem I have is with reading the fired cases.
The first loads I made were with the bullet around .005" (yes, .005) off the lands and all of the loads had cratered primers.
The second batch were with the bullets around .030" off the lands and the cratering went away and some of the primers were backed out a bit.
The third batch were with the bullets .090" off the lands, and some of the loads have primers significantly backed out of the pockets.

So my question is: Is the primer backing out an indication of too low pressure? I suspect it is, but I would like a sanity check.

thanks

Backed out is normally too low, yes.

It wouldn't hurt to dig for some factory .338-06 ammo, just for comparison.

Cratering is more of an indication of the fit of the firing pin to the hole in the bolt face, than anything else. Don't ignore it, but don't read too much into it, either.

Sounds like quite a rifle. Got velocities of those test rounds? That would be useful information.

Might want to have a gunsmith run some go-nogo and field gauges in the chamber. E.R. Shaw is a known barrel maker, but no telling who cut the chamber and how well they did it. Backed out primers are sometimes associated with incorrect headspacing.

The rifle sounds like a pretty nice used one.

Fellas, this is interesting. Can you educate me on why a low pressure load or incorrect headspacing can produce a backed-out primer? Does the brass "grab" the chamber first before it backs into the bolt? Thx.

You got it. The firing pin drives the case forward, the case grabs the chamber wall, and there isn't enough pressure to stretch the case or, if the chamber is slick enough, let the case slide back to the bolt face. The primer is in it's own little world, and backs up. The Hornady #4 manual illustrates this nicely.

Bye
Jack

Thx Jack. I should read the front of the manuals someday!

Shawn/All...

Give the front of the manual... IF you post/read on here, you're enough of a gun nut to enjoy most of the information provided...

Nate

If your chamber is oversize you might still be able to fire form cases for it to make it usable. You will have to reload for it. I would suggest makeing a chamber cast. Once that is done RCBS can make you a set of dies for it.