Chamfered firing pin hole mimic primer cratering?

[hunter24605]

I thought I was seeing signs of high pressure at the range because the primers looked to be cratered..Closer inspection at home, the primers still have nice rounded edges and not flat..Seems to me in an over pressure situation, the would flatten first then crater..But looking at my bolt there is a pronounced chamfer around the firing pin hole..I may be off base, but I think this chamfer may be the culprit for the "crater"..The "cratering" does go away when I reduce the charge a good bit, approaching the minimum..This is a new model 70 CRF bolt... These are CCI primers

 

[truck driver]

I have two push feed models that do the same thing and makes me think it is a Win thing.

 

[hunter24605]

My dads old (pre-64) 264 WM doesn't do it unless it is an over pressure situation, but this one is a new (made in SC) CRF. I guess everything, no matter how good, has its little idiosyncrasies you just have to get used to......

 

[truck driver]

I have a batch of Rem 35 Whelen brass that the primer pocket has a wide chamfer in the primer pocket mouth and the primer comes out looking like a rim fire when discharged. Drove me nuts for a while since the loads were under max and shouldn't have showed signs of pressure.

 

[PJGunner]

That is a noticable crater but the firing pin hole does not look that bad. I'm thinking that the very slight chamfer plus a slightly oversize hole for the pin is the cause. I have several Winchesters that do that even with underloaded cartridges like the 7x57. What's even worse is a Remington M700 that shows a deliberate chamfering of the firing pin hole. As I bought it NIB at retail store, it definitely had to come from the factory that way. Even light cast bullet plinking loads show a pronounced crater. Still, I have a stiff 180 gr. load that clocks 2800 FPS with the Hornady bullet and no apparent pressure problems. Two other Remington M700s do not have that chamfer. Wonder what some idiot at the factory was thinking?
Based on that Remington and what my several M70's do, I wouldn't worry overmuch about those craters. The ones from my Remmy look about the same as yours BTW.
Paul B.

 

[hunter24605]

Supposedly the chamfer is to prevent the firing pin hole from becoming a "cookie cutter".

 

[jimbires]

I'd say you're fine . it looks like the firing pin hole needs a bushing so it fits the pin better . I have a rifle that does this too . I thought about sending my bolt out to get it bushed , but I haven't . I've never blanked a primer so I guess my bolt is acceptable . " gre-tan rifles " is who I was going to use for this .