I wish I knew, but I don't pretend to understand the M21 market-just glad I have one- thanks mucho, Dad. I went to my 1938 Winchester Sales manual page 40- shows the cross-sectioned details of the adjusting screw and locking bolt, but no details on the inset spring in the barrel lug-- The third graph left column- halfway down- "It is particularly desirable for women shooters who have difficulty exerting strength enough to break (open-my add) the ordinary double gun. This ease in operation should be capitalized and is an excellent selling argument"!~ Perhaps this is why the late Ernest Hemingway bought 2 used 20 gauge M21's- one for third wife Martha Gellhorn Hemingway, and after the divorce and she left the gun with Ernest, he had acquired another one with 2 barrel sets from A&F, and his last wife, Mary Welsh Hemingway used that-- Personally, I believe the Ithaca NID model is the easiest boxlock double to open, recock and close--
To respond to the comment made by my "Parkerista Amigo"-- Sr. Murphy- yes- true, but perhaps this was addressed by the final sentence in the afore-mentioned paragraph circa 1938-- "The hinge on the double gun is extremely strong and cannot be ripped open by slamming the barrels open (I assume, with the forearm in place)-a thing that is not permissible in competitive double guns.
As my Dad's M21 (sn 15992) was made before WRA made it a special order item sometime in the 1960's (at a $1000 list price) and I am NOT familiar with those later production M21's- they modified the spring assist-barrel stop mechanism in the barrel lug- Never having seen one, I cannot say. M21- AISI 4140 alloyed steel heat treated and single fitted after that process, had to be an expensive fitting operation- not that the "double fitted" with case hardened AISI 1020 forged receivers and components as employed by A.H. Fox, Parker Bros., Hunter Arms and Ithaca was not--
I am loath to advise other gents here how to spend their gun $- but I would prefer to find a comparably equipped Ithaca NID and buy and use that- If you bought a decent field grade M21 for, say, $6K, and the "wolf came to your doorstep", would you be able to liquidate that very same M21 for what you paid for it??
