I bought a Mueller for my 870 20ga. It does not have mounting hole. I checked local gunsmiths and they wanted $25 per hole to drill and tap, so I tried a B-square from BP that was on sale for $25. Sat way too high. Had to take cheek completely off stock. Talked to Remington, they said a scope mount for a Remington 7400, or 7600 would fit the contour of the 870 20ga. Warne part # A995M fits perfect. Ordered a drill and tap set from MidwayUSA, $5.99. Screws are 8-40. With the Mueller down on the receiver, cheek weld is fine. Waiting on drill and tap set, will post pic when complete. Hope this is helpful.
Randy