Adding a sight rail to a Springer M3 shotgun?

[Mr. G36!]

Hey hey! Been thinking of throwing a reflex sight on top o' the ol' M3, but all of the rails I've found for such a purpose are for real steel, and attach via body pins...body pins that are purely cosmetic etchings in the body of the springer shotguns.

Ideally, I just want a nice, clean rail up top, so I'm just brainstorming some ideas. I guess I could just drill & screw a short rail into the top, but I don't wanna damage it. Then there are some cage-style pistol rails that I might be able attach with some modifications, or maybe even something designed for an MP5 or G3? Kinda fugly, but if it works, it works. And last but not least...maybe there is an actual sight rail for a springer shotgun that I just plain never heard about.

Anyone got any other suggestions, dos, or don'ts that might help me out?

Thanks!

[Styrak]

Hot glue. And/or epoxy.

[Jimski]

you can't really use something that goes around the body because of the shell ejector and the trigger guard...

if you pierce make sure you don't go through the piston/cylinders...
I've put a rail on mine, but it's for a flashlight, so I screwed it on the side using very short and wide pointy screws; even then I put the rail on top of two rubber blocks to avoid the screws damaging the 'mechbox'.
seriously for airsoft application I'd just glue the rail on top of the body with epoxy.

Styrak beats me to it!