I didn't have any 9x21 brass in my misc. box. So, I trimmed a 38 super comp. brass to .833 length. And it seemed to fit fine. FWIW , a 38 super brass ( .900 ) sized in a 9mm die was to long.

I'll have to see if I can find some real 9x21's to try.

I've been using 147 gr cast and FMJ in my 9x19 brass and I'm quite satisfied with the accruacy of my 929. And since I have a 5 gallon bucket of 9x19 brass I probably won't be switching to 9x21 brass any time soon.

But it is,, verry interesting.