I’ll add to the warning.

300 MP is a slow burning powder from what I am told. If your hull batch is slightly different from someone else’s, you could experience different results. For example, some hull-wad-powder combos don’t always shoot the same as your buddy’s batch he bought a year ago. If you are shooting a gas operated semi auto, you may experience your hull coming back in the chamber prior to full ignition. This will cause the sides of the hull to blow out instead of forcing the shot down the barrel. This is because the explosion from the powder forces the hull in the direction of least resistance.

I’ve experienced a batch of hulls in the past that would not allow the wad to seal and the powder charge leaked around them. This creates a dangerous situation because the wad would stick in the choke. If you fire a shot with a wad stuck in a choke, the back pressure created is going to blow the barrel up in your hand, or cause other components of the gun to fail.

These cases are few, but do occur. It’s not just with 300 MP. Be careful and heed warnings from those who have experience. If something isn’t right when you shoot, don’t just keep going and always make sure there are no obstructions left in your barre after a dud if you experience one.