Measuring Internal Threads

[4GSR]

do you have the old barrel just measure that. if not look up the specs of the thread in the machinery handbook and make a plug gauge to match the specs test fit it if too loose make another on slightly larger do this until it fits like you want it then thread your barrel bill

Or you can use my thread program to make a gage to.

http://www.hobby-machinist.com/resources/thread-program.2496/

Ken