Blown Primers

[mattd]

so been reading a little on the subject. sounds like if the gas is blowing between the primer and the case then the case is suspect. if there is a hole in the primer then the primer itself could be faulty.

i had 9 out of 49 blow and it was a hole in the primer right at the bend/corner of the cup. the brass has been well used, about 6x fired. mostly med loads of 44mag, maybe 2 firings were hotter loads. this load, with all the failures, was 265g bullet, 9g Unique, Win LP. Otherwise the brass is in good shape. i've used these primers out of the same case for many other rounds with no problems. could it be that the pack of 100 is bad, or could it be the brass?

[john hayslip]

The two reasons primers usually blow is too much pressure or a firing pin that is too sharp - they should end in a hemisphere and fill the hole the firing pin goes through. The case is usually not the problem if the primer is held in place by friction. Another is getting the thinner pistol primer in a rifle cartridge (just ask me how I know about that one - blush)

[country gent]

A light firng pin / hammer spring cncause this also . The firing pin isnt supporting the primer under pressure like it should. In the corner as you describe may be a defect from the forming process as metals tend to thin when formed into bends and radiouses. Make sure your priming punch is flat and square. no sharp edges to cut nick.

[Outpost75]

If the puncture is in the knuckle radius of the primer cup, and not leakage between the primer pocket and the exterior of the primer cup, the primers themselves may be at fault.

I was at Camp Perry in the 1970s and gave Tom Sharpe at Remington a piece of my mind because our military team had experiened a large number of blown primers, as you described. I had so many that they actually cut a ring around the firing pin opening in the boltface. I returned the primers (100,000 of them!) and got four new bolts fitted in team rifles which has been damaged.

Metalurgical examination of mounted, sectioned and etched primer cups, showed under SEM that the sheet stock from which the primer cups were blanked, had been exposed to ammonia fumes. Sure enough,further investigation by the government determined that somewhere between the brass mill and Lake City AAP there had been a train derailment which resulted in release of anhydrous ammonia from a tank car. The government condemned that lot of brass sheeting, but instead of the contractor sending it back for remelt it was tucked away somewhere, and I always knew it would turn up again....

[saint_iverson]

Wonder if CCI or a diff primer in the exact case and same load out will have a similar failure, or different batch of win

[1hole]

"...a hole in the primer right at the bend/corner of the cup."

It's bad primer cups from a bad roll of brass the maker got from the foundry, it happens to all of them occasionally. If you can't swap the rest save them for lower pressure loads and they'll probably be okay.

The burn spots in the breach face are cosmetic, it's harmless, won't harm anything.

[Outpost75]

"...
The burn spots in the breach face are cosmetic, it's harmless, won't harm anything.

That was NOT the case in damaged M40 and 40X rifles I worked on for repair. Repeated pinhole ruptures had actually etched a ring around the firing pin opening of the boltface, which was deep enough that case heads would deform from plastic flow into the bolt face, causing hard opening and rub marks on case heads. Remington replaced four bolts for us.

[DGV]

There has been a ton of discussion on this. Even loads with safe data. The common link has always been Winchester Primers. Some brass has a sharp radius in the primer pocket. Remington in particular. I personally pitted the bolt of my Marlin 1894. I was using 19 grains of AA9, Remington Brass, 260 grain 429421, and a Win large pistol primer. Not a hot load. Do a search. I am convinced Winchester had a bad batch of Pistol primers get through. I am in the process of contacting Winchester.

[mattd]

There has been a ton of discussion on this. Even loads with safe data. The common link has always been Winchester Primers.

i have always thought the Win primers were soft or weak or something. they seem like the flatten easily with moderate loads. not exactly like i can just go buy more primers tho.