Question about mounting FF on 870 20 gauge?

[dms2511]

Im looking to build an 870 (20 gauge) for my next project, and i assusme they dont come tapped on the reciever for a scope mount. I anticipate purchasing a burris FF2 to mount. What is the recomended method, and do i need to utilize services of a gunsmith?  Any help is greatly appreciated.

[Chuck1443]

Yes, needs to be tapped for a 336 mount