Didn't want to tag onto the already started threads about using a false shoulder when you have some short brass and don't want to overstetch it on firing. But yesterday I formed brass to a 257 Roberts AI from once fired 6MM brass. I just was trying it and didn't think to lube the case........050 difference base to shoulder measurement from the 6mm brass to already formed brass. That's a LOT. Plus it's taking the taper out, so I got a stretch ring little more than 1/3 of the way up the case from the rear part of the case grabbing the chamber and the tapered part being free to stetch forwards from there. It didn't all stretch there or it wouldn't of held, but there was a spot that took the brunt of it.
Tried it again today and lightly lubed the length of the case body up with 5w 30 synthetic. Slippy and light. Just a speck on my finger slicked up the whole case. Worked like a charm. Spread the stretch out over the length of the case. Carefull inspection revealed no visible part that was stressed.
Pic is of the formed case next to a once fired 6mm. The formed case has the same base to shoulder measurement as already formed 257 AI cases, so formed out to the T on the first firing.
Tried it again today and lightly lubed the length of the case body up with 5w 30 synthetic. Slippy and light. Just a speck on my finger slicked up the whole case. Worked like a charm. Spread the stretch out over the length of the case. Carefull inspection revealed no visible part that was stressed.
Pic is of the formed case next to a once fired 6mm. The formed case has the same base to shoulder measurement as already formed 257 AI cases, so formed out to the T on the first firing.
