I'm fairly new to the 9mm. I've had one for a number of years but haven't loaded much for it.
A while back I got a deal on 1000 once fired 9mm cases. Most of them are military and still have the original primers. I haven't used them but got them out this morning to load up a few. I miked a few and found them to be between .735 and .745. The specs call for a trim to .751. Just how short can they be anyway? What happens if I shoot a .735?

I have never measured or trimmed 9mm brass, and I have never had a problem. (I do gauge loaded rounds.) If the military cases are crimped around the primer pocket, you will have to swage them.

As long as the firing pin can reach the primer and hit it hard enough, it goes bang. Is that length after sizing? Because they will shorten up on firing and grow after sizing. They probably shade the short side so the pistols will run better dirty, but they obviously worked the first time. Might depend on your gun.

I resized a few and found that they grow about .007. The one's that measure .735 are now .742, very close to the minimum .744. I guess I'll load up a bunch and see what happens.
Thanks for the info.

Saami luger diagram is .754

For reference 9x18 makarov is .713

I have never trimmed a straight wall brass.