Barrel Threads revisited
 

A barrel thread is specified by its "pitch", expressed as the number of threads per unit of linear measure, its "form", or thread profile (square, V-type, etc), the "thread" angle formed by the sides of the thread, and the diameter of the threaded tenon. Over the years gunmakers have combined these parameters in a seemingly endless variety of barrel thread patterns.


The Whitworth thread system, the British standard from the 1860's to after WWII, was a 55deg V-form thread with rounded thread crests & roots. The American National screw-thread system, standardized in 1933, used a 60deg thread angle with small flats at the crests & roots.


Though the Whitworth and American National were both inch-based measuring systems (that is, the pitch was expressed in threads per inch), their different thread angles led to interchangeability problems. In 1949 great Britain, Canada and the US adopted a Unified Thread system that retained the 60deg angle of the American system but permitted both flat and rounded crests. Many older foreign actions like the Luger employ a V-type 55deg Whitworth-type barrel thread. Current American, British, and Canadian actions generally use a Unified barrel thread. Metric barrel threads are also found on a number of foreign actions. Now uncommon, square threads were once popular, and can be found on the '03 Springfield, M1917 Enfield, M1 garand, and others.

Thanks for the refresher History Lesson Hugh...
 

I know I had that information filed away in my head somewhere, but my filing system is beginning to need some work...


regards,


John

Re: Barrel Threads revisited
 

Rick, if they are of recent manuf, I pretty sure they are 60 deg.

Re: degrees
 

Rick,


I just checked the Luger barrel tap and die set that I have and it is marked: N18x1.27, which I assume would mean a National thread, which would be 60 deg.