It makes sense that it was something specific to that rifle. I have a Model 70 in 300 Wby. with a short throat. That rifle will shoot a 200 grain AB at 3050 fps using 79 grains of 7828 in Federal cases. I have some cases that have been fired 5 times with that load before starting to get slightly loose pockets....at which time I throw them away.

The same rifle will take 80 grains of 7828 with a 200 gn. Partition at the same velocity (with Norma brass) with no problems at all.

Chet