During a shoot i had a shell 12ga gold medal hull tear and send about half of the hull down the bore. It made a very loud report and recoiled a lot. The gun sucked up most of the recoil. Everyone in my squad said double charge.I knew better but could not change their mind. So i set out to double charge a shell. I was correct the volume of red dot was too much even for the 9000h to mash into the case.The shell was jagged where it separated.Of course the most important thing was i did break the teal target.any ideas i have been reloading multi-projectile encapsulments for 25 years and have never seen this before.
Without seeing your hull, I can only hazard a guess. I imagine that what you got was a “whistler” where the entire front part of the shell case, wad and lead separates and goes down the barrel almost like a slug. It may open a bit and let some of the shot out because the target is often hit. This happens ALL the time with Winchester AA .410 hulls if you load them too many times. I can’t tell you how many times I have pulled the rear half of the .410 AA hull out of my Model 42 because I loaded it “just once more”.
My guess (hazarded) is that your Federal Gold Medal was none too new and finally burned through in mid section before it gave out at the crimp. That will do it. Solution: toss the hull out one reload before they do that! Uh huh.
Shotgun Report’s Technoid
(Often in error, never in doubt.)