You can use a pipe cutter without damaging the barrel. I've done it on plenty of plain brass barrels. As long as you keep the pressure low, you can do it safely. Granted, you should still clean up the edges once it's cut, either with a dremel tool to grind out the inner edge, or if you have a lathe, turn it clean. Even better, if you put a crater cut back in the tip if you have access to a lathe.
Hopefully there's just one kind of pipe cutter out there and I'm not feeding incorrect information that will cause some one to mess up their nice barrel. lol.
I don't think a Dremel tool would be a good idea. The heat it generates can cause some minor warping to the metal.