More pictures to inspect……. Notice, that there is a proofmark on receiver, just very light. Also, no caliber marking on bottom side of barrel and no rework numbers visible. I have requested that the owner look closely for any other markings on barrel such as a m/o proof or possibly some more numbers farther forward on bottom side of barrel.

Steve

Maybe I missed it, but do we know, based on the receiver serial number, what year the rifle was made?

Interesting!!!  A few observations/comparisons:

According to figures quoted in David Bichrest’s book, a total of 50,145 M54s were assembled 1925-1936, with the last remaining inventory sold by 1941.  So this rifle would have been assembled using one of the last couple thousand receivers made, PR date probably 1936, by which time M70s were being assembled ahead of their January 1, 1937 release date.  Perhaps the receiver was a leftover that had never been made into a gun before 1939.

In my experience, and claimed in Rule’s book, pre-war H&H barrels were rarely caliber stamped.  Later ones, seems to me, are often marked “300M”, but pre-war ones tend to be unmarked, as on 1938 this 300 MAGNUM standard barrel:

The ’39 barrel date with its separate “54” stamp is coincidentally (???) similar to Tedk’s 30 GOV’T’06 M70/54 mail order proof barrel that I posted a pic of yesterday.  His hand stamped “54” barrel is also a ’39 M70 part.  This is underneath Tedk’s barrel:

The subject rifle inletting does appear to me to accommodate the long 300 MAGNUM magazine box (second pic from left above).  For comparison, this is the inletting of two 1938 M70 standard rifles, one in 300 MAGNUM and one in 30 GOV’T’06:

All in all, I’m inclined to think this M54 “bull gun” was assembled within the factory in 1939.  Since the M70 bull gun had been in production for 3 years before this 28″ EH 300 MAGNUM bull barrel was made/marked “54”, the rifle wasn’t a M70 prototype.  Either a M54 Sniper’s Match owner wanted his rifle converted to the new/hotter 300 MAGNUM, or someone within the factory (employee?) put it together from spare parts as Steve suggested earlier. 

Much of my speculation that it was factory work is based on the barrel being marked M54 and the presumption that the barrel was factory marked.  Would Winchester create a part for a gun that didn’t exist, i.e. M54 in H&H chambering, and send the part out to be installed on an action that couldn’t handle it?  I suppose, maybe, if it was being sent to some renowned gunsmith with factory connections (???).  But if the “Average Joe” gunsmith was going to do this conversion at home, wouldn’t he have needed to use a mail order M70 bull gun barrel that was marked M70? And why, in that case, change the model designation to “54” from “70”?  It wouldn’t make it shoot any better…  That the barrel is marked M54 makes me think that the factory would have wanted to oversee the action/stock modifications necessary to make the rifle functional.

Just my ignorant take…  And thanks to the OP and Steve for this interesting puzzle…

Lou

That the barrel is marked Model 54 leaves me wondering.  I suppose if the barrel was ordered from Winchester for a M54, they simply marked it that way?  Could be that simple?  Also, isn’t it possible the rifle was sent to Winchester for rebarreling – and the customer specified rebarreling only with no changes to the action? The fact that cartridges won’t fit in the magazine does not surprise me.  As the rifle sits, it’s a target rifle.  And like many target rifles, it is fired in single-loading fashion.  Why would a target shooter pay to have the action reworked to make it a repeater?

It’s been an interesting mental exercise and I’ve enjoyed all of he opinions and comments.