I would order a go gage and a no go gage if you are inexperienced. You can get them at midway or brownells or other big dealers. You screw the barrel down to touch the go gage and tighten the nut without moving the barrel.I usually bring it to touch and back off about a 32nd of a turn and then tighten the nut.Now recheck your work with the no go to make sure it doesnt close on the no go. If it does,loosen and try again till you get it right. The problem is if you tighten the barrel nut with the barrel right on the gage it can turn the barrel down tighter due to the nut dragging the barrel slightly tighter then you may need to.