2 packages of Bell .25-20 SS basic brass came my way a couple of years ago. This was the stuff made in the late 1980s. Out of 40 cases, 36 survived their first full length resizing. The other 4 split during the initial sizing. I loaded up the rest with 5.0 grains Unique and breech-seated an 85 grain bullet. After the first few split, I tried one with no bullet, just like shooting a blank. It split also. then I dumped the powder out of another 2 and fired them with only primers. They both split.
I salvaged the powder & wads and took the remaining cases over to my friend's shop. He heated each one with a gas torch and dumped them into water. I reloaded them with the same 5 grains of Unique load. (I shoot a Stevens 44 action stamped 47 EX on the front of the action). This time they worked OK, groups about 1.5 inches at 100 yds, but I noticed that a primer looked loose. Then I took the next fired case, put it into my mouth and blew hard. (OK, that makes me a blowhard.

) But I was able to blow the primer out of the case. So the heat treating process softened up the heads or somehow increased the primer pocket size.
I have one of those old hand reamers that was intended to cut the crimp out of GI primer pockets. So I used that to enlarge the primer pockets of the surviving cases (still have 15 or 20) and use large pistol primers. Seems to work OK, but what a lot of work. I have about 20 old REM-UMC cases that seem to just keep going.
I also have 40 Bertram .28-30 cases that I have never used. Do these cases have the same propensity to split?