I , recently almost bought a Colt New Service in 44-40 to compliment my 1894 Marlin (early one , 3 digit serial #) in 44-40 . My Marlin as what I would call the perfect barrel . The groove diameter is .426 . I cast / size my 200 RNFP bullets .427 . The case necks only expand about 1/2 thousandths when fired . The throat is that snug .
Now , back to the Colt I almost bought . I had been wanting a New Service for quite some time . I was excited to find one in nice condition at my local gun shop . I felt I should have the cylinder throats and groove diameter of the barrel measured before committing . The owner has a local gun smith so we had him measure them . The owner of the shop called me back yesterday to tell me it had came back and it is " serviceable " . I thought , what does that mean ?
It turns out the cylinder throats are .427 and the groove diameter of the barrel is " .433 " , really ! I am not sure you could get a cast bullet that size in the case w/o crushing it . Needless to say , I'm glad I did a little research before buying it , I passed on it . Regards Paul