I know what you are thinking, and I don't think that's what happened. I have been reloading for over 10yrs and never had this happen. This is a rifle I built 110 Savage with a McGowen barrel in 270 Win. I have put a little more than 100 rnds down the tube working up loads and shooting deer over the last 4-5 yrs. The round in question was a brand new Nosler brass. I bought them about the time they started selling brass. After inital load development with Berger 150VLD's I bought a new box of bullets and 100 pcs of the Nosler brass. This was the first loading. I got load data from Berger Bullets via email. I need to look in my book but I think its 52.5grs of H4831SC (going from memory and need to check my book). Anyway checking sight in a couple weeks ago I fired one round it was on etc. Dialed scope up 6" just to check its function and fired one more rd. Once again on target. Opened bolt, easy ejection etc. Picked up brass and the primer is gone. Later found the primer in the mag well, it looks fine not blown out or deformed in anyway. I meant to put this up on a forum earlier but just thought about it again. I am going to see how a new primer fits the suspect brass. I guess it was either a faulty primer or a bad primer pocket. It was a winchester primer. Any reports on bad brass from Nosler? That is my prime suspect.

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Seat a new primer into the pocket and see how well it seats.

Federal Brass does that...gets loose after a couple of loadings.


Could be an out of spec piece of brass.

Sounds like out of spec brass or primer. Try measuring the primer if you still have it with a mic and the primer pocket. the idea of testing with another primer is good also.

I agree. No cratering or flattening with the primer blowing out is a sure sign of an enlarged primer pocket.

check primer pocket size.. and mic your primers.. just to check them.. mic that bullet primer pocket with other brass that you have

52.5 grains is right at a minimum load acording to Hodgdon website. I'm showing that load to be 45K psi at normal COAL, which is under the minimum pressure level. So, I think you are running too light of a load and getting pressure spikes from this light load. (If you are certain that you are using this powder and this charge)
I never like minimum loads with slow burning powder. You can easily get pressure spikes. If you want to run a light load, switch to a faster burning powder, and your pressure issue will go away. I'm 99% sure this is your problem.