I am working with a customer on what will eventually become the SM-2, a pistol grip 870 that is awesome. Same high quality components, but a Speedfeed pistol grip.
If you are thinking about adding a pistol grip to your shotgun there area a few things to remember. The first is that you must have an barrel length of at least 18″ and the overall length of the gun must be 26″. This last one is a little known fact, but ATF is serious about this one as well. Make sure you don’t overlook this one.
A true pistol grip will only work on the 870, not the 1100 or the 1187. The recoil system on the semi-auto shotguns runs through the stock. The 870 doesn’t have this. Speedfeed offers several pistol grips on full stocks if you need one, but not a true pistol grip.