Where can I find a quick-detach scope mount for my remington 870 express magnum? I want to put a red dot sight on it for turkey season, but I want it gone for pheasant season...

Take a look at the Knight's Armament Co. 870 Rail Adapter System (RAS), p/n: 99143.

Available from Wes and Paul at www.mstn.biz

Enjoy,
havoc

remington offers a cantilever mount for their vent rib barrels. it attaches via a milled slot on the underside that fits over the rib, and a flat retangular plate that secures from the underside of the rib by four screws thru the top, and it also has two small set screws on the side to apply lateral pressure from the mount to the rib. makes for a strong setup. the top will accept standard "weaver" rings. by mounting to the barrel, zero isn't changed from sling or other outside pressures. i think it's around $40.00
i have one on my express magnum with a pro-point, hasn't dissapointed me yet.

why not just tap it?