Does the marlin base require drilling and tapping to work on the 870 or will it mount to the current holes ?
If your 870 is drilled and tapped from the factory, the screw holes for the 336 mount will not line up. You will have to drill and tap two addition holes, as the hole pattern is spaced different and the screw sizes are actually different. I had the same problem and I elected to drill and tap two additional holes as the 336 mount sits lower to the receiver and just makes a cleaner look. With that said, I used the Remington base and factory holes on another 870 and went with the Burris picatinny mount. Both of them worked really well.
Thanks for the info......I believe I'm just going to go with the picatinny mount.
Drill and Tap it for the 336 base if you can get the base. I have a problem getting them is only thing I see.