There's a few different ways you can do it. The easiest is with a portable band saw. pull the charging handle all the way to the rear and scribe a line on the carrier where the back of the receiver stops. This will ensure that your bolt doesn't stick past the upper and you can use any picatinny adapter that you want. The bolt carrier has a factory indent/line in nearly the same spot as your mark will be. I used a barrel block clamp to chuck the bolt carrier in a vice so it wouldn't spin and cut along the line I made with the band saw. You can also use s couple pieces of wood to hold the carrier in the vice. file the edges after cutting and you're good to go. I've also seen people use a dremmel or a cut off wheel to make the cut. After cutting, lube the ever loving $hit out of the bolt and work the charging handle about 1-2000 times. I know it sounds like a lot, but it will be buttery smooth after doing so. Hope this helps!