WWII M1911A1 Barrel

[Mikecp@2022]

My M1911A1 mfg by Colt left the factory by February 17, 1943 to Springfield Armory.
This gun has a Springfield blue barrel marked on left lug S P and a heat lot number AG1.
Now could you explain what I read about it; Also found in some new 1943 contract guns.
Is that possible this gun left the factory with a field replacement barrel? Or this has been changed at a later period. I must add the gun does not wear any arsenal mark as AA, RIA, SA, RA...

Information

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[Johnny Peppers]

Colt made their own barrels, and did not use barrels made by anyone else. The barrel could have been replaced at any time in the past almost 70 years. The other 1911A1 manufacturers depended on contractor supplied barrels, and while High Standard was not up to full production some field replacement barrels were used.

Remington Rand even used some Colt supplied barrels in the late 1942, early 1943 time period.

[Mikecp@2022]

Thanks for reply, that's what I though but wasn't sure, the only phrase intrigued me found on the book of M. Clawson was: Also found in some new 1943 contract guns
I try to get a proper COLT AUTO 45 with small or large G but impossible here, because its the only part missing to have a perfect pistol, well! Wait and See...
All the best.

[Johnny Peppers]

The key to the information found in the Clawson book is "Also found in some new 1943 contract guns", but not in all guns.

[Mikecp@2022]

You're right, I was wrong, but my language is french, so I'm not sometimes as accurate with English as I should be...

[Promo]

IMHO that would be ACP for Automatic Colt Pistol, there should be a .45 somewhere aswell

[Mikecp@2022]

Well, from the Joe Poyer book these are 'Heat lot numbers' as:
AG1, AG-1, BF1, BH1, PX-1, PX-8, REP1, REP2.
I do not know exactly what means those, maybe a proofing barrel test.

[Johnny Peppers]

IMHO that would be ACP for Automatic Colt Pistol, there should be a .45 somewhere aswell

The AG1 identifies the heat lot number of the barrel. Doesn't have anything to do with caliber. Only Colt stamped their WWII barrels with the caliber, COLT .45 AUTO.

[Promo]

Usually guns in EU need to be fire proofed, this includes markings of the caliber aswell. I've attached a picture showing such markings:

[Johnny Peppers]

The 1911A1 pistols Lend-Leased to England had to be proofed before they could be sold commercially after WWII, but the sale of these pistol did not start until the 1950's. The British Proof Act of 1955 required the caliber marking.

No caliber marking was required at the time the pistols were manufactured.