[The Viking]

I have a friend who had the bottom blow out of a Glock 21. Turns out he seated the bullet too deeply.

 

[roundball]

Seating too deep. I had a narrow escape with a Smith 28-2. I had loaded some rounds for my Smith Model 19. Seated the bullet back enough to crimp about the top band. That was on the Keith SWC. Don't try it! Gun Gods took care of 28 and me. Also, I stopped right then. Maybe OP would have been served better if he stopped shooting the loads that KB'ed his gun three times.

 

[roundball]

I had an event that was new to me loading 40 S&W for my G23.4. I had set up the 550 for 40 caliber. I was using Power Pistol powder and 155gr. Hornady bullets. I prefer to check my loads as I go in the 550. Early on I had an unusually low charge when weighed. Basically, it looked like the powder had bridged or stuck in the base of the Winchester brass. Brass was clean and had been sized and set through the Redding push through die.

Full charge plus: This bridging happened several more times. The charge was not excessive when all the powder was in the case. Was it possible to put case back into the 550. The case would would have the correct charge plus the powder stuck in the bottom. This would not be a happy thing.

In all my loading I'd never seen this thing. I am wondering if this bridging, powder stuck in the bottom of the case, could have to do with the KB's in 9mm and 40S&W.