870 older 20 gauge to 12 gauge conversion/parts interchange

[AJAX22]

I picked up an old 870 20 gauge receiver assembly for cheap and would like to build it up.

I heard a rumor that the early 870 20 gauges were all actually 12 gauge receivers and could be built up as either 12,16, or 20.

What other parts are interchangeable?

Are the Mag Tube's all 12 gauge as well on those older 870's?

Are the bolts/triggerassemblies/stocks/barrels interchangeable?

I don't mind building it up as a 20 gauge, but since it is missing a number of pieces If I can build it up as a 12 gauge it is more practical for me.

And yes I know that it will probably be more expensive than just getting a new one... but in my state we can only get tax stamps for C&R SBS guns.

Thanks

 

[mnrivrat]

As your gun is pictured it can be set up to shoot 12ga. by changing the shell stops and the bolt assy. If my recall is correct that is about it. If you don't have the 20ga. barrel for this receiver they can get hard to find for the standard model, and you may be better off converting to 12ga. in order to find parts.

PS: Yes the stocks and trigger housing would be the same for either the 12 or 20 with the possibility the forearm wood for the 20ga. might have a smaller channel for the barrel, but I'm not sure it did.

 

[AJAX22]

What differences are there in the bolt assembly on a 12 gauge and a 20 gauge? Does the whole assembly need to be replaced or just part of it?

will current production 870 shell stops work?

Thanks for the info

 

[mnrivrat]

I think the only difference in the bolt assy may be the bolt body itself. The face of which is a different size of course. Extractors, firing pin, etc may be the same.

Shell stops should be the same as present production.

One thing I did think of is the ejector may be different - not sure, but possible and it should be looked up - I haven't the time at the moment. This part is rivoted onto the inner side of the receiver and may protrude in farther on the 20ga. ?

Used parts can be looked for on Gunbroker and Auction Arms - ebay used to list bolts on a regular basis but I think they are banned now.

 

[AJAX22]

Very cool,

I think I've found/ordered most of the parts I need to complete this project (I still need to get the tax stamp and won't be doing the machinework untill that is done)

But I'm really looking forward to seeing if this works as easily and straight forward as I think it will.

Thanks for the help.

 

[Pinion327]

Any progress on this? I'm in the same situation...

 

[mgkdrgn]

I'm curious ... I would think it would be cheaper to just -buy- a 12 gauge 870 than to build one from parts.