What is it and why??

[Riflemeister]

What is it and why?

well I looked this case over quite well and besides the obvious, the base of the case was flatten out from the case being slammed against the bolt face. I can hardly think of any circumstances were this would be a reasonable course of action!

Therein lies the big problem with headspacing on the belt. The magnum headspace dimension on the reamer prints is .220". Most mag brass you check with calipers will be somewhat short of that. I just checked some Win 338 mag at .215". Now add the factory headspace tolerances that could add another .003" to .004" and now you are approaching .010" of free movement in the chamber on firing. There is the reason most knowledgeable reloaders treat their belted magnums as rimless cases after the initial firing. The fact that all that occurred when the 300 Win Mag was fired in a 300 Weatherby chamber was a little flattening of the case head speaks volumes about the safety margin built into modern rifles.

 

[papapaul]

That headspace lash you mention exists in most belted mags. Knowledgeable reloaders headspace on the shoulder because they can. They can control that headspace. there isn't much they can do about belt headspace without gunsmithing.

 

[Paul H]

That headspace lash you mention exists in most belted mags. Knowledgeable reloaders headspace on the shoulder because they can. They can control that headspace. there isn't much they can do about belt headspace without gunsmithing.

Kinda tough on my 458 lott

 

[papapaul]

Yes, you are correct. My .458 headspaces closely on the belt because I set it myself. I was just addressing the comment about "speaking volumes" about extra strength. A flattened primer on a belted magnum will have a cause, but not because it isn't headspacing on a shoulder.