SHORT CARTRIDGE CASE QUESTION?????

[bullseye308]

Here’s a thought, if you have a bunch of short cases, just shoot lighter weight bullets in them at the same OAL.

 

[LiveLife]

Let us say the cartridge trim length is .750

Yes, the caliber is always helpful when answering questions.

Based on .750" trim length, I am thinking OP is using 9mm.

When I did myth busting/confirming for 9mm OAL variance based on headstamp, measuring various headstamp "resized" case lengths measured .750" to be average median so I used .750" length cases for the myth busting - https://www.thehighroad.org/index.p...e-consistent-oal-on-progressive-press.921633/

Let us say the cartridge trim length is .750 but the cartridge only measures .746 to .748 and all the oals are the same, what could happen?

No, relax and be happy. It's OAL you need to be careful with.

If the OALs pass the barrel "plunk test", shorter cases will allow the case rim to drop more towards the chamber. And if case is like 9mm that "headspace" off case mouth, shorter cases will move case mouth/neck further away from chamber (Especially when fired) until held back and "headspace" off the extractor when chambered (Essentially dangling freely in the chamber).

With really short cases, you will experience more gas leakage as longer cases that headspace off the case mouth will readily expand case mouth/neck to seal with the chamber to leak less gas. And more leakage translates to lower/inconsistent chamber pressures ... Which could result in more muzzle velocity variance and coupled with bullet drop (If shooting longer distances), vertically elongate bullet holes to produce larger groups.

Of course all these could be overshadowed by shooting variable of shooter input on trigger/grip to move muzzle/POI away from POA.

 

[foxmeadow]

RCBS makes the X-Die, which supposedly eliminates the need to trim to length. The instructions have you trim your brass to .020" short of nominal length to allow the die to work its magic. Short trimming is not really that big of a deal, apparently..