I've had 870's for quite a while, and my 12-GA goes back together in seconds, slick as glass. I just tore down my new-to-me 870 20-GA to clean and swap stocks, and for the life of me I can't get it back together. If I slide in the forend WITHOUT the slide assembly and breech bolt, it goes together just fine. Once I try to add the slide block in the two action bar cutouts and add the bolt assembly, it jams just as the action bars get to the two shell latches. Sometimes I can get it to go in but the whole action binds up.

Yes, I've read the manual, and yes I'm following the instructions. I've tried it with and without the trigger assembly installed.

Any thoughts or experience with this?

Done. Don't ask me how you can spend the better part of 4-to-5 hours trying to reassemble these, guiding the action bars in or out, dropping the bolt block 8,725 times, using Vulcan chants and Harry Potter curses..... and take it to the LGS and the gunsmith does it in 2 minutes. Sheesh. Did find out that the 20-GA ejection spring is missing. Off to source that part.....

Sorry that I'm late to the party.

My old 16 gauge, which was made my Noble, is a huge pain in the rear. I swore that I would never take it back apart and clean as long as I own it.

Even the trigger pack on it isn't captured. It is just held in place by faith.

John A. wrote:... I swore that I would never take it back apart and clean as long as I own it....

I'm there with this 20-GA. The good news is that 99% of it can be cleaned and lubed without major disassembly and it's easy to access most of the internals with the trigger guard out and barrel off. I will have to (mebbe) take it apart once again to stake in a new ejector spring, but we'll see.