My new AR has a varmint upper from White Oak.  It has a nice FF aluminum forend, but is not drilled for any add-ons.

I want to add a small rail for lights.

I know I’ll have to drill and tap.

Who sells such rails and screws?  Any idea of  hole and tap size needed?

Ahh, a varmint entry tactical....hrough
We sell 2" ($15) and 4" ($25) Picatinny rails with appropriate holes and (inner) back-up alu plates with threaded holes, but they are "flat" dimensions in the 1/2 x 2" contact area. Your FF HG is obviously a curved surface.

There'd be too much wobble potential and possibility of tearing loose for drilling and tapping the tiny diameter screws that would be appropriately sized.

I would through bolt, using washer and NyLock nut. I would take up the 'slack' from the curvature issue with thin neoprene, maybe even self adhesive strips laid along the two edges. Any way you do it, you're going to need to fill that gap to avoid loosening and wobble/stress. A machinist could make you the appropriate filler, I have made many a botched attempt at doing such things for my personal use, that's why I am not a machinist.hatand it is designed to fit the curve.  $65

Doc @ M&A  Parts   847 550-8246 9-5 cst m-fri