Primer Pictures -- Pressure Opinions?

[Josh Smith]

Hi Folks,

I went from 0.318" bullets to 0.323" bullets in my Gew88/05 Commission rifle. The 0.318" bullets were just causing problems.

Here are some pictures of primers. The brass is 7.92x57mmJS (8mm Mauser) formed from Winchester .30-06 brass. Bullets are 150 grain Hornady. Powder charge is 43.5 grains of Varget, and primers are Federal Large Rifle. Published velocity for this load is 2400fps, which is just fine. Figure it might be a bit more with the tight bore.


Two different exposures with their inverted images on the right side


Macro uncut

The primers look like they're fine to me. Do you agree?

Data is from Hornady and the 43.5 grains Varget is their starting load. Hodgdon's starting load is 45.5 grains. Figure I'm safe using 43.5 grains as a start and 46 grains as max -- do you agree?

Also, this is effectively a squeeze bore. The initial slugging of the bore resulted in a groove measurement of a little over 0.318", but subsequent cleaning and shooting have been peeling off grime to reveal something a bit bigger. I still need to slug it again, but it may end up being 0.321" as they were playing with sizes of 0.318" to 0.321" while developing the rifle, and I have an original 1892 barrel. For now I'm assuming a groove diameter of 0.318" to be safe.

Would you have an estimate to what kind of velocity the barrel adds if it's 0.321"? I'm not trying to push the rifle's limits at all; just curious. I know there were squeeze bore barrels made for the .22LR before the advent of the rimfire .17 calibers, and they boosted by a few hundred feet per second.

Subjectively, recoil is about like a .30-30 with 150 grain load, maybe a bit less. Feels good to shoot and if I can find an accuracy node someplace under 46 grains Varget, I'll be a very happy camper.

Thanks!

Josh

[Burrhead]

Josh just to look at the pictures they look ok from here in Michigan. Have you mic'd the diameter just before the extractor slot against an unfired case? this is also a good indicator of high pressure. But the primers look good to me.

[tjtM38]

I don't see any smoky primers, cratered primers or any unusual bolt marks on the back end of the cases. I would say you are fine.

I don't know much about the mausers; have only owned a Yugo M48 in the past. It was .323 diameter (8 x 57JS), but I understand bore diameter can be a real issue on the older rifles. That is probably why most commercial mauser loadings are very conservative and lower velocity.

I would love to own one of those old 88s.

[Sgt. Rob]

The primers look fine to me, but that is not always indicative of high pressure in every circumstance. And being that you are using an 1888 comission rifle I would not tempt the max load. The starting load should be fine. Roughly speaking, every inch of barrel beyond the test load theoretically increases velocity I believe from 20 to 75 FPS depending on the caliber. Really not enough to sweat about in rifle shooting and barrel lengths.

Semper Fi, Rob

[Dragunov sniper 777]

federal primers are softer than most other primers , they will ripple and flatten or flow out of the primer pocket easier than others , that and them being more sensitive is why a lot of people use them , without pressure test equipment we really don't know how much in the red zone we really are , but , there are ways to tell without the other , like measuring the case heads and OAL before and after firing , a sure sign you are in the danger zone is sticking cases {difficult extraction } and a hard to unlock bolt .