Thread: Converting Colt A2 upper to Flat Top

Mill a corresponding step profile along the bottom of the rail to match what's already there on the upper.

If it were me, I'd buy a length of rail off trademe, or use a bit of hand guard rail (you know that tactical shit that people love to hand forward grips, torches, lasers and rocket launchers off). Those rails are normally thicker, longer and dirt cheap to buy.

https://touch.trademe.co.nz/listing/view/1079582946

If not thick enough, make some packers out of aluminum to sit it level.

Use existing taped holes...job done