A bit off a silly question and slightly off thread, but here goes
Would u be able to fit an extra shorter shell in the mag as surely the mag is only an 2" or so longer than the normal mag, so even if u went down to 65mm/2 1/2" game shells i'd imagine very tight to ger an extra 1 in.
3.5" x2=7" mag 3 x 2.5" = 7.5"
Not very familar wi semi's so could be well known that u can fit an extra 1 in, and do they cycle the shorter rounds ok