So, I’ve been bouncing around a few M4 pages, and came across an A.R.M.S. page on impactguns.com. While I am very much impressed with the rail setup, one thing did catch my eye: the foregrips in the pictures. They look almost identical to the rear grips next to the trigger. My question is this: is there an adapter (picatinny/weaver) that attaches to a traditional grip?
http://www.impactguns.com/store/ARMS-58M-MOD.html
http://www.impactguns.com/store/arms_sir.html
^^^^^
The links that the pictures are on. Any clue on the optics would be a help as well.