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Gunsmithing #3B contour length and 5/8-24 threads

BoilerUP

Old Salt
Full Member
Minuteman
Jan 16, 2011
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Floyd Co, IN
I see on LRI's website that they recommend cutting a #3 contour barrel no shorter than 18" in order to have at least .725" for 5/8-24 muzzle threads and a .050" shoulder.

Can anybody with experience tell me if a #3B would have .725" @ 20 inches?
 
Do you mean no longer than 18” for a #3? Go to the contour page and get the taper per inch for that portion the barrel(takes a bit of easy math) . Then subtract from the finish length that amount for every inch you shorten the barrel. 5/8-24 threads are .625 in major diameter.
 
I see on LRI's website that they recommend cutting a #3 contour barrel no shorter than 18" in order to have at least .725" for 5/8-24 muzzle threads and a .050" shoulder.

Can anybody with experience tell me if a #3B would have .725" @ 20 inches?

A Bartlein 3B contour will have a muzzle diameter of .725" at a length of 23.5". The diameter at 20" will be .760".

They are .700" at 26 inches and get .010" bigger for each inch shorter.