New vs old Blackhawk barrels.

[pony express]

Seems I would like to have a 3 screw Blackhawk in .41 Mag. Of course I could just buy one, but.....I have a pair of .357s, and one is not that great cosmetically, some cleaned rust pits on the barrel. Soooooo would it require any extra machining to fit a .41 barrel from a New Model (assuming I ever found one)?

[Mustang Gregg]

I'm not 100% sure they use the same thread.  But I recollect they do.  

Better ask one of the Ruger 'smiths.  I recommend Run N Iron in Nebraska.  
You can Google search for them.  Lonnie and Blue are top notch!!

Here's their address....www.runniron.com.

Mustang Gregg

[buttebob]

OM barrels have shorter shanks than NM barrels. NM barrels can be fitted to OM frames, but not the reverse. Notice the word "fitted". Machining will need to be done.

[pony express]

Hmmm... sounds like it would just be easier to buy a three screw .41 instead of building it.