Was decapping about 1,300 pieces of once fired 7.62x51 last night when I came across this one.
I can't imagine it being intentional, but it sure is interesting.
Headstamp on the 7.62 is FC (I think), but I can't make out a date. Headstamp on the interloper is MIY 99 (or 66). It's very hard to see, but when I look down inside the case mouth, it appears that the inner case is there, and has expanded to the inside diameter of the 7.62 case.
Did I see something else like this on here recently?