Headspacing troubles

[Krazong]

Did someone mess with your sizing die? Maybe it was resized too far? Are you full sizing or neck sizing spent cases from YOUR rifle only?

[Ds J]

Is the primer pockets loose in the cases with blown primers?

The primers fall out completely and have much play in the primer pockets. The web and rim of the case is so enlarged that it does not fit the shoe of the reloading press.

I have regularly found a small ring on the primers from this batch of cases. It looks like a little wall around the dent made by the firing pin. Every time I checked speed, everything was on spec so I never bothered with that.

Did you measure the velocity of the shots where the primers were blown?

No. I calculated the average volume of a batch of almost 200  PMP cases, then used QL to calculate a safe load for practice. Then I loaded a batch of cartridges with the safe load.

Who loaded the ammunition?

I did; I started reloading 33 years ago.

Were the cases annealed by you or someone else?

No. Most if then were once fired when I received them. They have not been fired more than five times. Thrice is probably correct.

Have you had any head-case seperations?

No. The two cases I have show lines which might indicate it.

What is the case growth per shot?

I have never measured that in my life.

A carbon ring will give pressure every shot so we can discount that theory.

The rifle stays accurate, but these "blown" cases usually throw the bullet towards the low right side on the target.

Did someone mess with your sizing die? Maybe it was resized too far? Are you full sizing or neck sizing spent cases from YOUR rifle only?

The chances for someone messing with my dies is fairly small, simply because I am the only one handling it.

I tried neck sizing for a while and went back to full length sizing after I couldn't load a cartridge on a hunt.

[JamesNotBond]

No. Most if then were once fired when I received them. They have not been fired more than five times. Thrice is probably correct.
quote.
You speak of these cases as received 1 x shot, are the second hand cases? If so can we then agree that these cases could then be almost any number of times shot.

[Ds J]

No. Most if then were once fired when I received them. They have not been fired more than five times. Thrice is probably correct. 

You speak of these cases as received 1 x shot, are they second hand cases? If so, can we then agree that these cases could then be almost any number of times shot?

I know/knew the original owners of the cases. They bought factory ammo and did not reload. Thus I received (most probably) once fired PMP brass from them. I did not count the amount of times I reloaded them. Given the amount of shots fired, I did not reload them more than three times.

[janfred]

"The primers were indented at times, and sometimes pushed flat, and blew out three or four times."

"The webs of the blown cases were far out of specs."

"The primers fall out completely and have much play in the primer pockets. The web and rim of the case is so enlarged that it does not fit the shoe of the reloading press."

"I have regularly found a small ring on the primers from this batch of cases. It looks like a little wall around the dent made by the firing pin."


The above are all signs of high pressure loads. Enlarged webs can theoretically be caused by excessive headspace. Cratering can also be caused by an overlarge firing pin hole in the bolt.

Enlarged primer pockets can only happen with more pressure than the brass can handle. Couple that with the expanded web, sticky bolt lift, primer cratering and blown primers, then overpressure or soft brass are the only explantions.

So, you may have excessive headspace. That can easily be solved by setting up your sizing die correctly. I do not believe your blown primers are as a result of excessive headspace. I believe that you also have a problem elsewhere with regards to loading.

How do you measure the charge weight; powder measure or scale?
Where did you get the bullets from? Are they all the same brand, model and weight?

The only other way that you can get excessively expanded webs and primer pockets is if the web itself was annealed. Which is difficult as you used these cases before and you didn't anneal the brass..

In your shoes I'd scrap the whole batch and start from new. I'd also check each bullet from this batch for weight and shape. And weigh every charge.