Recoil of Benelli M4 vs 870 with Knoxx Stock

[MannytheGreek]

So I've been thinking about a Benelli M4,

I really like my 870 with a Knoxx Stock- the recoil impulse is significantly dampened. I was thinking about purchasing a Benelli M4 for a semiauto and was wondering what the recoil characteristics were like compared to my 870. If you get the collapsible stock does this improve things?

Thanks!