Quote Originally Posted by jtwalker View Post
Sounds like you have an 878 barrel (which was a semi-auto) on an 870. My quick google search shows that an 870 barrel can be used on an 878 (but no gas ports means it will not cycle), so maybe an 878 barrel can be used on an 870 (and blow gas where it shouldn't). That's my guess.
Did some follow up on what you said. There was a Rem 878 Auomaster semi-auto shotgun produced back in 1959-?. The markings on the 878 barrel match my barrel. The 878 barrel has "MOD" and well as AFCO" marke din similar areas and in the same style. Thanks!