- Joined
- Jun 9, 2016
my little secret to adding an optic rail to old police shotgun receivers (since the fillister screws really don't have much meat to secure the rail to the top unless there's like 5 or more of them and even then it's not a good way if the shotgun is roughly used regularly) is to machine in four 3/32" holes spaced two closer to each other in the rear and the other two evenly set towards the front of the section, open up the screw holes on the rail section to 1/8" and remove the threads, then epoxy in some 4140 aluminum pins made from round stock. the pin head has a square shoulder and prevents the pin from falling through, it's replaceable/removable, and the epoxy holds them in place very easily. optionally if i know this is permanent i can braze it in place (titanium filler from blue demon works great for small stuff like this) and it isn't going anywhere even with 3.5" 12ga or 10ga magnum loads.I never have faith that factory mounted rails that aren't integral to the receiver (regardless of platform) will stay put, so the first thing I did to my Mk IV was to pull the rail, degrease all the relevant surfaces and use blue LocTite - never had an issue with it for a couple of years. Did the same when I swapped that rail out for a TandemKross RMS-C mount and I'm pretty sure it'll be fine too.
the cheap method is just drill and cut 2 more threaded holes for two additional securing screws (i like using 8-40's since they will usually match the factory screws) or using the Mesa rail mount. i dislike modifying the side of the receiver since on an 870 if that ejector breaks it's annoying to remove, so the "sleeve" style that uses enlongated trigger pins is better imho.
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