I am wondering if it is common for these primers to fall apart after they have been fired I am using 300 gr mz expanders with a 120 gr of shocky loose powder in my black diamond 50 cal

I've fired quite a few of those and I haven't had them "fall apart" on me. Can you post a picture of one after this happened?

No. Sounds like the breech plug needs attention.

I have never had that happen, but have pretty much decided to stick to 777 primers or Federal Fushion primers.

Not at all normal, especally with that type powder. Check the touch or flash hole that sits next to the powder for flame cutting.

I agree , the only time i have had a primer blow apart was when the carbon was built up so bad i was getting a ton of blow back from the primer and it pushed the center out . I have shot 100s of Remington primers and only had it happen one time . If you have a tight fit/seal you may not have any blow back and it blowing your primer apart . Here is what mine did after my breech plug was plugged with carbon .

here the peices of one I recovered

DUDE! That is definitely not right...

I supect he has the old type open breach plug with a spring on it, not recommended for BH209.

lemoyne

You are correct, the Black Diamond is an open breech plunger style ML. Anytime you shoot a reall potent load with either BH or T7 you stand a real good chance of getting primer, battery cup and anvil separation.