I made a set of these out of Oak and thought I saved the day then saw JP Rifles makes them. They sell a set for $95 (on sale at Midway for $75) and these guys have the same thing. Mine cost .50 cents. No matter what upper you have that is full picatinny, no handle, it works great. http://www.squirreldaddy.com/AR15-Pro-Al...20-124.htm
I just took the oak board and mittered a 1/2" slot down the center of a 6" long piece of scrap oak so it goes from the front pivot pin to the rear take down pin. Then took another piece and cut a 7/8" grove for the picatinny top. I have held many of uppers in the vise to install barrels with barrel nuts and no movement or marring. I guess the one Klem posted is to hold the barrel but I haven't needed that. This block holds it rigid enough for installing the gas blocks and my comps. I never torque it so much it will twist the barrel as I've read people saying you might. So go ahead and ding me for saying that now and explain why what Klem posted is needed... I just haven't seen the need.
I just took the oak board and mittered a 1/2" slot down the center of a 6" long piece of scrap oak so it goes from the front pivot pin to the rear take down pin. Then took another piece and cut a 7/8" grove for the picatinny top. I have held many of uppers in the vise to install barrels with barrel nuts and no movement or marring. I guess the one Klem posted is to hold the barrel but I haven't needed that. This block holds it rigid enough for installing the gas blocks and my comps. I never torque it so much it will twist the barrel as I've read people saying you might. So go ahead and ding me for saying that now and explain why what Klem posted is needed... I just haven't seen the need.