I use one of those gun vises that I picked up from Wal-Mart. Stick the gun in the vise, aim dead center, fire one shot, reaim dead center, then adjust your crosshairs to where the bullet went in. Then shoot for groups and adjust as needed.
Do not use any kind of gun vice with a rifle with heavy recoil,because if you prevent the gun from recoiling,you place a great deal of strain on the stock,and/or the action screws.I have seen stocks cracked because of this,and action screws bent if the recoil lug was not fully bedded.
As well,guns often don't shoot to the same point of aim out of a gun vice.