As Issued 1944 IBM M1 Carbine

[USGI]

To change the subject away from the rear sight for a minute, is that cut across the barrel just behind the front sight a bit unusual for an IBM barrel? Also, I can't help but wonder, with the many thousands of parts that were integrated to IBM from several of the prime contractors, wouldn't it be a bit unusual for an IBM carbine to have all IBM marked parts? Isn't that sear a bit early for that serial number? Maybe it turned up at the bottom of a bin just as this one was being assembled? I only have one IBM, and it's got and NPM trigger housing, Inland bolt, and a Niedner front sight, but it could have been built that way. - Bob

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[BrianQ]

To change the subject away from the rear sight for a minute, is that cut across the barrel just behind the front sight a bit unusual for an IBM barrel? Also, I can't help but wonder, with the many thousands of parts that were integrated to IBM from several of the prime contractors, wouldn't it be a bit unusual for an IBM carbine to have all IBM marked parts? Isn't that sear a bit early for that serial number? Maybe it turned up at the bottom of a bin just as this one was being assembled? I only have one IBM, and it's got and NPM trigger housing, Inland bolt, and a Niedner front sight, but it could have been built that way. - Bob

The " cut across the barrel just behind the front sight" is found on all IBM made barrels.

Published integration records show roughly 465K parts were integrated to IBM. IBM delivered 346,500 carbines. If you take that info at face value one could claim there was no such thing as an all IBM carbine. However, when you start looking at the parts that were integrated roughly 200K of the 465K were parts you could not identify as being made by or for a specific manufacturer, parts like springs, pins, screws, etc. Discounting the non-identifiable parts the percentage of integrated parts to carbines delivered gets smaller. Period records also indicate a lot of integrated parts were used to fulfill the spare parts requirements of contracts in addition to being used to assemble carbines.

[USGI]

The " cut across the barrel just behind the front sight" is found on all IBM made barrels.

I only have the one, but it doesn't have the cut like the OP's IBM. - Bob

[DaveHH]

RPW: Timelines: most carbine makers were done, gone, finished by April 1944. That is the fourth month. Type 2 and 3 rear sights were just getting rolling about Feb-March of that year. Do you think that any of the other makers would be sending scarce adjustable sights to companies that were done a month later? NPM who never put anything but flip sights on their carbines sent IBM 20K assemblies in Feb 44. I have two carbines that came from the factory with type 2-3 rear sights, neither has any stake marks beyond the two used to secure the adjustable base, dead center in the dovetail. My NPM has a type 2 added in a rebuild it has both the punch marks and a very subdued chisel mark from the flip that used to be there.

[BrianQ]

I only have the one, but it doesn't have the cut like the OP's IBM. - Bob

Sorry, thought you were referring to the "I" cut under the front sight, which all IBM barrels have and is visible on some even though the front sight is installed properly. Some IBM barrels have an additional cut aft the "I" cut.

[majspud]

Sorry, thought you were referring to the "I" cut under the front sight, which all IBM barrels have and is visible on some even though the front sight is installed properly. Some IBM barrels have an additional cut aft the "I" cut.

https://www.milsurps.com/images/impo...Barrels1-1.jpg

Curious about the plain versus grooved barrel. As mine is very late production, is it a deleted milling process, early vs. late? Or are the little 'ribs' to aid in heat transfer to cool the barrel more quickly?

T