Would MGC cartridges branded for :-

M39, Sig P210, Sig P220 be compatable with each other I've no dimensions to compare directly, but they're all 9mm and their rims and rim grooves look very similar.

Would they be the same overall length I wonder

I do not know about MGC cartridges, but in real life all three guns are standardized on 9x19 Parabellum ammunition.

Length is often overlooked - I still remember trying to load 9x19 Parabellum in 9x18 Makarov gun, because I only checked caliber. Of course it didn't work (impossible to load magazine), and it took me quite some time to figure it out, as I thought 9mm is just 9mm ;-D

In theory the critical firing dimension is from the base of the cartridge to the top of the piston, as far as I know all MGC with the piston system have the same size primer inserts and pistons so they all should work with the same det pin length.

The other issues are overall length, the hole size in the front of the round and the shape of the tip.

One way to try is load up a few rounds with fired caps and see if it feeds/ejects then try it for real

8ace

Thanks for the info' chaps

Overall length can vary quite a bit, the MGC Beretta M92 cartridges are significantly longer than P220s for example.
Attempts at cycling them through certain models has the "bullet" tip hitting the base of the det pin for example.

Does anyone out there have M39, P210 and P220 cartridges they wouldn't mind comparing please