I've been using Mag Tech large rifle primers in my 500 magnum. The cylinder started locking up after every shot and I found the firing pin was stuck and would not return. I put a new pin and spring in, but after 8 shots today it's doing it again. Some of the primers are blown all the way through and others are kind of mushroomed back. I'm thinking that the primers are too soft for this gun and when they blow a hole in them the pin is getting fouled and burned until it finally locks. I'm using a very mild load with Titegroup and I have no problem even with strong factory loads. Any ideas for a harder primer would be appreciated. Thanks
Something is very wrong if you are blowing rifle primers. Some rifle calibers will develop upwards of 60,000 psi and won't blow a primer.
You said you are using a very light load of Titegroup so it's unlikely the pressure is excessive unless you are getting detonation. Even though it's very rare it could happen. I would have suggested your firing pin was damaged but you said you already changed it.
It's possible you have a batch of defective primers. MagTech primers aren't made here, they are made in South America. Before you fire any more ammo I would use a different primer company. I have always used either CCI or Winchester rifle primers with no issues. (mostly CCI) My first move would be buying some CCI, Winchester, Remington or Federal LR primers and give them a try and see if the problem goes away.
Please keep us updated, good luck...