Case head concentricity?

[osok-1k]

We all obsess over everything in a build and our loads be to the 'nth degree. True actions, bolt face being square to the bore, case neck runout and everything else associated with accurate shooting. I was loading some 270 Win. yesterday when I felt where the head stamp had peened proud of the surface. I took some fine diamond paper and a flat glass that I use for checking surfaces for flatness and the case head was anything but flat. It was cupped, the peening came off pretty quick but was it true to the centerline and body of the case? I've not read anyone ever talk about it, if that is the surface of a round from which establish datum points, headspace, OAL and other measurements we deem critical, why do we not ensure that this most fundamental baseline of all else be true and flat?

I pondered this for a while and thought that if one had a tool like the Wilson case trimmer that uses a case holder to align the case mouth with the cutting tool, why not turn it around and see if the case head is true to the body. A very light skim cut should tell the story. I though of setting one up in a lathe with the case head facing out but too many of us don't have a lathe and the Wilson tool seemed reasonable as I'm sure there are lots of loaders with one.

I don't have one but I've been thinking about buying one for reaming necks and cutting case length.

If I'm the only one who thinks this could be meaningful (I'm pretty sure I'm not) then feel free to disregard.

 

[AZShooter]

A guy at the range skim trimmed the bases of his cases on a Wilson trimmer. He swore by it. He was the only person I knew that did this. I knew two 1000 BR guys one who has a world record who never bothered.

The only time I found an issue was when a rifle I was asked to work up a load for had great accuracy with virgin but not once fired brass. I tried quite a few things, but the groups remained quite large. It was found that the gunsmith had opened up a non magnum bolt face to magnum dimensions for this build. He didn't open the face up enough! The case head was wedged into the bolt face. When firing the body conformed to the chamber but the case head became drastically out of true. Bolt face was opened up a bit more and issue was gone. The damaged cases were recycled.

 

[osok-1k]

Interesting, sounds like the person who modified the bolt face should have checked his work or at least corrected the problem.

It just seemed to be a plausible think to verify, for me I think I will incorporate it and see if it matters. Sometimes minutia is just that and has no real value.

 

[RichCoyle]

I did some testing with squared heads using the Wilson case trimmer and random cases. I proved conclusively, for myself, that in this particular 223 varmint savage rifle, the squared heads were definitely better with two different loads.

 

[osok-1k]

Excellent, thanks for the experience