Mac/M11/9mm people, maybe you can figure this one out:

[lurkersince03]

See that little rail past the trigger guard on the bottom of the reciever (toward the barrel)? The second picture has a foregrip attached to it. I have an original Cobrary M11 9mm carbine that I'd like to attach a foregrip on like that, but I can't find any information on that rail-piece. stonycreek has a tri-rail set up which would probably be better, however installing it would require a pistol-barrel set up, putting me in NFA territory. Does anyone know anything about the rail-piece in question?

 

[Flame Red]

I have never seen a rail like that, so I assume this is someone's own customization. Probably found a short generic rail and either rivited or screwed it on.

Personally, I would just go with this handle setup:

http://www.stonycreekarmory.com/store/catalog/product_info.php/cPath/23/products_id/36