McMillan now makes 4″ and 6″ picatinny rails that can be installed on stocks and used for attaching bipods, monopods, loops, lights, etc. Both the 4″  & 6 ” pic rails have a hole for a quick detach push button sling loop (not included).  Color is Black Anodized.

Picatinny rail sizes:

4″ OAL (over all length), 3″ hole spacing

7″ OAL (over all length),  6″ hole spacing