I got a 2NL on the internet. The cap fit funny and then did not fit at all. I looked at the threads. The male threads on the barrel were relatively course and the female threads on the cap were fine??? So I looked at pics on the internet and for 2NLs I see both fine and course threads on the barrels? So I got stuck with a mismatched cap but does anyone know the history of why two different threads on the same model?