300 win mag overpressure

[MagnumManiac]

I think the problem lies in the brass, and, or primer.
Federal 300WM is well known to be soft in the head, and the primer pockets loosen on the factory loading!
There has also been defective Winchester primers, both standard and magnum.

Look at the cases and the primers.

Cheers.
MM.

 

[nastynatesfish]

I have never used a magnum primer in 300 or 7rem mag. I've used everything from rl19 to retumbo. I think if you live where it's rediculously cold and are using a very slow powder you'll be fine. I thing using a magnum primer and warmer temps all your going to do is run into pressure signs faster than you would have

 

[Jeff Conover]

A split down the side of a primer cup, or a heavy draw scratch enough to cause the primer cup to split on the side will show as a primer gas leak with a pin hole look defect on the radius of the cup. Yes, it will cut your bolt face if you have these defects in the primer lot in your supply, you can expect 3 or more in 100 primers. Remove the spent primer and look to see if the cup has a split down the side. I know this happens with Winchester and Federal primers and the companies also know it, but they do not put out a customer advisory. If this is the case, contact Winchester and get instructions to return you lot of primers, the defective primer, and they may even replace your bolt.

By looking at primers under magnification and even without, you can see this defect. I have never had this problem personal, but I have seen some of my customers who have had with primer lots made in April 2014 time frame.