Your M2 will probably work fine with the low recoil slugs, but the only way to know for sure will be to test it. Be advised that if you hang more weight on the gun with things like lights, lasers, etc. you will reduce reliability of the recoil -operated system.
The Marines adopted the Benelli M4, which is a "gas assisted" recoil system in order that they might have a semi-auto shotgun that was ultra reliable with low recoil ammunition such as bean bags, rubber bullets, etc. The Marines like to hang a lot of stuff on their shotguns. They found that as they added weight in the form of lights, lasers, shell carriers, they reduced the recoil velocity of the shotgun and, thus, the reliability of the recoil system that depends on that velocity. The M4 adds a gas assist to the basic recoil system and makes it all completely reliable with virtually anything that will fit in the chamber. Your M2 should be OK with low recoil slugs but other ammunition such as bean bags may not be reliable.
