NOS stands for New Old Stock. Numrich Gun Parts had new 336A barrels about 10 years ago. I have a thing about buying extra barrels for the guns I like, so I bought two. The barrel comes with 2 dovetails cuts in the under side, one for the magazine stud and one for the forend tenon. The rear dovetail I filled with a sight blank and turned it down in the lathe. I then filed a notch for the band screw. I robbed a magazine stud from another rifle, thinking I could order another. Wrong, they are no longer in stock so I ordered one for a 1895 and will have to remachine it to fit the smaller diameter tube. I cut the original magazine tube down to match that of the A. I wanted it to look like an older rifle so I reshaped the lever. The headspace was under standard with the new barrel, but after smoothing the bolt face in the lathe it ended up standard minus .004 inch. The rim of most brass is undersize, so the action just closes. I have not shot any groups on paper yet to know about the accuracy.