I've had two cases split like this recently. They are 45 Colt, Winchester brass.
This brass seems to be thin and the primer pockets seem to be tight as well. The cases have been reloaded for the fourth time and the load is 7.5 grains of Unique and a 250 grain RNFP cast bullet, shot out of a 25-9. The primer set back some too.
I reload on a Dillon SDB and have done so for many years and this is the first time I have had split cases back to back.
This is the first Winchester brass I have ever used so I was wondering if anyone here has had the same or similar results?
