Probably a carbine length handgaurd then. It's standard across the industry, even with Colt having weird pin diameters, lol. Should drop in, no sweat. the MOE handgaurds install just like the standard handgaurds do, so unless you're getting a free float tube, it ought to be cake to put together.

Also, I love my Streamlight TLR-2s, for the record... I like having the option to use the strobe function, as well as the laser/light combo for fast hits. You would not be disappointed if you picked one up, but it does require a pic rail to mount. If you barrel mount, get an interface that goes to a picatinny.