Well mine ran great until I ran slugs through it. The bolt carrier failed sending the bolt to the back of the receiver. The trigger group was affected as was barrel at back of the chamber.
I replaced the bolt carrier and the trigger group, both with 870 parts. Then I found a burr at the back of the barrel and I fixed that. The gun still isn't working right. It won't extract the empty shells now after firing. I cleaned it and polished the chamber and will try it again tomorrow. This gun is soon going to be a target for me to shoot at with my CZ 858.