Hi quack1-

That’s potentially tragic… 

The M70 standard grade rifle, when introduced in 1937, came standard with a 24″ barrel.  However, an option was the “standard grade with short (20″) barrel”.  These are commonly called “carbines” by collectors, although Winchester never used the term “carbine” with any M70 variant.  According to the figures in Roger Rule’s book, there were a total of 7,197 M70 carbines produced.  I think Roger’s figures are based on “yearly net orders received” documents rather than actual production figures, b/c some of the former records exist while most of the latter have either been destroyed or are not publicly known to exist…  Anybody got info on the location of surviving documents recording actual production figures??? 

As for barrel date…  You are right…  The earliest M70 “carbine” barrels I’ve run across were dated ’32 (made during the first year of Winchester Proof Steel (CMS) barrels and well before even the M54 “NRA short rifle” was catalogued).  No doubt that some unmarked 20″ CMS (not Nickel Steel) barrel blanks made for M54 production were used on early M70s (the famous collector’s adage that the Winchester factory NEVER threw away anything being true in this case…).  Given that the M70 was first advertised in 1936 as “Available after January 1st, 1937”, one might assume that the barrel on your subject rifle could just as easily been intended for a M70 (since a couple thousand M70s were assembled in ’36 so that the factory had inventory available to ship on 1/1/1937.

As for the swivels…  Factory SG swivels on a standard stock are not at all common, but are plausible.  There are ways to tell the difference between a (rare) factory special order and a (more common) aftermarket upgrade…  Inside and outside…  Basically, the center of the SG swivel base put the detachable swivel in the same location as the fixed bow.  So if an aftermarket modification, the hole for the fixed bow would be still be there, in the middle between the two holes for the SG base.  On both front and rear swivels…  Easy to tell if you pull the bases off.  Also, the inletting inside the barrel channel is very different between the standard swivel that had a routed out opening for the backing nut and the SG swivel that used two knurled nuts.  It’s not hard to tell if the action is out of the stock…

Hope this helps…

Lou