Bob Leiendecker has been good enough to send me a batch of material for my work on automatic cannon and ammunition, one item being a curiosity. It is a note from Aberdeen Proving Ground, dated March 1957, concerning a 30 mm dummy round from Argentina which they had been sent to examine.
The round is 280 mm long overall, with a case length of 185 mm. These measurements are effectively the same as the 30 x 184B for the Rheinmetall MK 103, but the case is not belted, has a rebated rim, and is wider overall (rim diameter 42.5 mm, body diameter above extractor groove 44.3 mm).
Aberdeen noted that this dummy was not the same shape as the “regular rounds used in the 30 mm aircraft cannon Model 6RA-30”. The implication seems to be that Argentina possessed a 30 mm cannon designated 6RA-30 which was chambered in 30 x 184B - possibly they had got hold of some MK 103 and were interested in adopting it?
If this is so, then perhaps they were interested in boosting the performance compared with the 30 x 184B by using a wider case?
Lots of questions here: Fede, are you out there?