Late, but will tell a story on myself.
Back in the 1970's, there was no 7.62X25 to buy and I had a Tok. to feed. SO I converted both .223 and .222 cases. the .222's didn't need neck reaming (today we'd tend to neck turn them, but back then reaming wasn't looked on as a "sin") but the military .223's did. Reamed them and all was well. These thicker cases take less powder to reach fucntioning, and less poweder to reach a guestimate of "max".
Twenth years pass (I still have that Tok.) and a CZ comes my way. Being in a hurry, I grab up some of those Tok. reloads and head to the range. About the fourth or fith shot, notice an ejected case looks just like a 9mm case.
What had happened was that while those cases fit the old Tok's. chamber just fine and allowed a clean bullet release, this CZ had a tighter chamber neck. When fired, there was no room for the case neck to expand, so the bullet took the jammed case neck along with it...both bullet and case neck exit the barrel, and the straight body part ejected.
Haven't a clue to how high that drove pressure...but the lessons are: (1) check EACH gun's dimentions, don't trust that if it works in one it will work in the other. (2) Home made cases usually do not have the same internal volume, and loading data has to be adjusted. (3) If brass is available for a reasonable $, better to buy it than make it.
