Norinco M14 castle nut tread

0.595: nominal diameter of threads
32: threads per inch (this is what the thread gauge from your tap & die set will tell you, but it's not the whole story)
NS: Type of thread ( "UNS" which indicates a "special" thread)
3A: Tolerance class ("3" indicates a tight tolerance, "A" indicates an external thread)

That's for m14/m1a castle nut , should work for m305 too.
 
I thought the castle nuts were somewhat interchangeable , just the gas system/chamber threads were not. I have a usgi castle nut on my m305. It fits , maybe I got lucky.
 
Back
Top Bottom