On most rifles, cases showing a cratered primer pattern indicate that the chamber pressure is getting high, perhaps dangerously high. However, in my case, I was using relatively mild hand loaded ammunition. In fact, when my gunsmith assembled the rifle and test fired with factory ammunition, he reported the same cratering.
I did some initial internet research, and found this is an increasingly common "problem" with Remmington bolts. Apparently, Remmington is making the firing pin holes larger than they used to, and what happens is that pressure from the fired round causes the metal case of the primer to "flow" inside the firing pin hole a bit. This is what happens with an over-pressured round in a "normal" rifle, but apparently it happens with Remmingtons with standard, safe pressure loadings. Most owners reported this as an annoyance, but nobody reported any problems caused by it. Rumor is that Remmington argues this makes primers less likely to pierce...I'm skeptical (both that they make this argument, and that it is correct). Looks can be deceiving, but it seems to me the primers on the left are more likely to pierce than the ones on the right where the primer cup is more intact. If a primer pierces you get hot gas directed in the wrong direction!
The problem I see is twofold besides potential for piercing. For one, now there is one less indicator that indeed a hand load round is over pressure limits...the cratering is a false positive. Second, which is not really a "problem", but anybody who picks up your brass at a match will think your rounds are too hot. This happened to me, and the shooters next to me were concerned, and rightfully so...if my rifle blows up they are in the shrapnel zone! I convinced everyone my loads were light, but the cratering still bothered me.
So I ended up sending my bolt to Greg at Gretan Rifles. Greg does some kind bushing to the firing pin hole and turns the firing pin, basically making hole smaller. He had my bolt back to me in under a week and everything worked great, as you can see the primer strikes on the right from the exact same load. He even has a web page to explain the process, although he was more than happy to explain it over the phone. It was $82, arguably unnecessary, but to me it is worth the piece of mind, and I'm very happy with the result.
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I agree with everything you wrote and your action in having the bolt modified. Remington's justification is lame.
ReplyDeleteJeff Chosid
That stuff about primers less likely to pierce is hogwash. More flow of metal = thinner section and more deformation + less ductility at area affected by the deformation = primer pierce.
ReplyDeleteMike-
ReplyDelete1. Keep in mind what I read about Remington's response to a concerned customer was all (Internet) hearsay, I don't know that Remington has an "official" position on the situation one way or the other...other than that I read several places on the Internet that they don't consider cratering to be a warranty defect...but again all hearsay and I could be wrong. I don't think Gretan would be in business if it were a warranty defect one could just send the bolt in to Remington for repair. So maybe Remington's position is that it's neither a "feature" or a "defect" and not a safety issue?
2. I suspect you are right...but I don't know enough about piercings to really agree or disagree. When a primer pierces due to over pressure, where exactly does it tend to pierce? The tip of the firing pin, or somewhere along the base of the protruding firing pin? Maybe it is counter-intuitive that somehow a larger firing pin hole (within limits) is actually safer?
3. Pragmatically, if it really were a safety benefit, then all the other manufacturers would be moving towards bigger firing pin holes as well.
4. The thing that irks me is that even if one takes the position that Remington is cutting corners lately...how hard or expensive is it in this day and age to make a (fairly) precise pin/hole match?
In any case, getting it "fixed" was definitely worth the piece of mind, even if it was only cosmetic.
Are you using soft primers? IIRC, some brands use softer metal than others. I think bushing the firing pin hole was a good choice.
ReplyDeleteThe primers on my loads are Wolf, which are known to be on hard side. The gunsmith who test fired the rifle used Hornady factory ammo with similar results, but I don't know what brand of primer Hornady uses.
ReplyDeleteI used the exact same primer (and nearly identical load) in my Mauser and never had cratering.