I want to swap out the A2 flash hiders on a couple of my AR-15s. I originally bought an upper receiver block for this purpose, but before using it I did some more research and found that holding onto the receiver is not recommended for changing muzzle devices, in part because some builders torque a flash hider to the same level as the barrel itself. So, I believe the best way to proceed is to clamp the barrel itself near the muzzle. I've looked into commercial barrel vises and don't like most of them. My concerns are (1) cost, as I'll only be using this a few times, and (2) commercial ones are often metal and I don't want to mar or crush the barrel. So, I'm thinking about making some vise blocks out of wood to hold the barrel in place inside a conventional vise, without marring it and hopefully without crushing it. Barrel OD will be .75" typically, and I was thinking of taking two flat blocks of 1" wood, drilling a hole where they meet (while clamped together) so that each one has a channel that can fit around the barrel, finishing that surface with varnish to make it stickier, and using that. Here are my questions: 1) Any reason this wouldn't work? 2) Should I use hardwood or softwood? This ties in with... 3) If I make wooden vise blocks like described, is there any chance I would still crush the barrel? I definitely do not want to harm accuracy of the rifles, and I've read that using aluminum blocks can potentially change the bore shape where the barrel has been clamped, which is bad. 4) Will I be better off with the channel as a semicircle or a right-angle "V"?