Barrel length is usually measured with a cleaning rod inserted into the barrel until it touches the front of the bolt or in this case, with a tape measure from tip to tip. I would make sure that it is slightly over 18" so that you don't end up with a length slightly less than 18".
People cutting barrels like this usually cut down to 18.5" or 18.25" to be safe.
Duke1
PS. This probably has been mentioned before but just in case, report the change in length of barrel to CFC to update your registration information.
People cutting barrels like this usually cut down to 18.5" or 18.25" to be safe.
Duke1
PS. This probably has been mentioned before but just in case, report the change in length of barrel to CFC to update your registration information.