cgv -
The M1 Tactical has apparently been discontinued and from what I can tell, been replaced by the M2. I can't say what the difference is between the M1 and M2, but both are inertia recoil operated systems. They are NOT gas operated. The M4/M1014 ARE gas operated. If you need a detailed description of this system, look at the Benelli site. The reason the inertia recoil operated system is sensitive to the amount of junk you hang off the gun is because if you hang too much off the gun, it will not recoil enough to cycle the action. To clarify, the gun will not move back under recoil enough to make the system work reliably - the extra mass soaks up the recoil energy and results in less rearward movement of the gun. Same thing for light loads - they may not make the gun recoil enough. This is why - based on what I've read - the M4 was developed. It is a gas acutated system, so it doesn't matter if you hang a kitchen sink off the gun, it will still function.
The M1 does recoil pretty hard, despite being a semi-auto. It recoils more, IMO, than my plain Rem 870 pump. My M1014 is on the way, so I'll evaluate that when I get it. I can't comment on the differences between the M4/M1014.
Rob
