I have already disassembled and cleaned everything. Reallly well too. I threw all of my cleaning supplies at it in stages switching when I got bored. MP7, CLP, Kroil, JB bore cleaner, Otis, dewy rod with brush, boresnake. So it is really clean.
Only part I havn't taken off is the magazine tube / recoil spring on the M3. It seems to be on the receiver very tightly and the manual doesn't show how to remove it so I didn't mess with it.
As I recall without getting up or referring back to my original post The Federal Game load I had was 3-1/4 but only 1 oz so maybe that will make the difference.
I wouldn't think that failure to cycle and hold the bolt back on the last shot wouldn't have anything to do with a worn out recoil spring. Would it? This is a pretty clean gun but it is approx 12 years old.
I'll try to find some more powerful shells.
Until then, any other ideas?