the mechanical principal on the franchi and the stoger are all inertia driven like the SBEII, just different levels of quality in the parts. a friend's franchi's internals look very similar to my SBEII. even the bolt head is the same shape, just a little different in size.
the bolt has a 'leg' that drives against a spring behind it, housed in the stock. the mechanism uses the entire weight of the gun to work the action. i know it sounds goofy, but the only way the gun won;t work is if you have your shoulder against a tree and fire.
the A5 rattletrap used the weight of the barrel and the bolt only. they are neat guns, but like JLD said, they are pricey IF you can find them.
to me, the 11-87 is HEAVY. though, it makes for good recoil absorbsion. my SBEII will kick shooing 3 1/2's.
like i said, i almost NEVER shoot 3 1/2's any more. mostly 2 3/4's and 3's. if i was buying again, i might go for the M2 for the comfortech or the franchi.
dennis