APS shell ejecting 870 Mk1 or mk2

Quite a performance difference between mk1’s & mk2’s mate

mk1 is compatible with mk3 shells and are “gas in shell” type

mk2 is a gas bolt, which unless you want to hpa it, is a bit naff

just a bit of info for you in case you didn’t know ? 

enzo47 52

Posted March 31, 2023

 I was told the dimensions on mk1 on mk2 are same . I have a spare mk1 bolt I wanted use to switch to mk1. sold my 870 serbu shorty which I regret. was hoping get hand on another or something similar in size. I've got sia 870 with about 100 mk1 shells. hpa did cross my mind but is it possible ?