Thank you very much for that JFL; so “MAT” = Manufacture d’Armes de Tulle. So, the link that I have (in the right side of my pics) is for a French 20M621 in 20x102?

I wonder what the “7-80” white ink stamp is…lot number perhaps?


For WMR,

the 24K is the link for the French anti-aircraft 20M693 in caliber 20x139.

the 23TE is the link for the French 20M621 in caliber 20x102.

Both links are derived from US M12 and are very similar besides the fact they accommodate cases slightly different in diameter. Although the 12,7x110 is a modified 20M621 weapon, the link which was used is that for the 20M693 (24K) … presumably because the case diameter of the 12,7x110 is closer to that of 20x139.



Many thanks JFL; I appreciate the clarification!


Aberdeen Proving Grounds report EFFECT OF VARIOUS DRIVING BANDS ON THE AERODYNAMIC PERFORMANCE OF PROJECTILES AT HIGH VELOCITIES, 1946: dtic.mil/dtic/tr/fulltext/u2/492607.pdf

Pre-engraved .50 steel projectiles fired from a gun with a “20mm breech”.

0.50 Pre-engraved projectiles WW2 a1_zps4lt0xafd

0.50 Pre-engraved projectiles WW2 a2_zpshv3xjfo5

0.50 Pre-engraved projectiles WW2 a_zpsctlsftniFigure 1

0.50 Pre-engraved projectiles WW2 b_zpsvglmughj

0.50 Pre-engraved projectiles WW2 c_zps4ng3cnl1 Figure 3


Brian, thanks a lot for this great report!

Thanks for the info!


Can these images be fixed as well?