870 magnum breech bolt & slide block

[pele]

Aloha! Im a new member from Hawaii & I need some knowledge from y'all. I have a 870 magnum & removed the breech bolt & slide block to disable the 870 for safety. However, these parts were lost. I want to know if my 870 magnum parts I ordered are the right ones. the parts I ordered were Rem slide block for a 870 marine in 12ga. & the Rem breech bolt assembly for a 870 12ga. police in matte color. The parts do actually install but the breech bolt is not locking up & will not cycle. can you send a little knowledge & suggestions my way brother? Thanks in advance!

[Synchronizor]

Any 2.75" or 3" 12ga 870 should be able to accept a modern 12ga magnum slide assembly & breech bolt assembly. Those parts have been updated since the gun's introduction, but the new versions are backwards-compatible for older shotguns. Your gun is a standard 12ga, correct? Not a 12ga Super Magnum or a 16 or 20 gauge model?