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Top of Receiver Nose Pin Punch Mark on M1 and M1928A1 TSMG's


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Is the punch mark that is seen in both the photos below something that was done as part of an arsenal rework? I noticed it on am M1A1, and an M1928A1 Thompson. I just don't recall anything being discussed or written about such a marking. please correct me if it's mentioned in a book.

 

Here is is (kind of blurry) on an M1A1 Thompson. The barrel has also been punched in the same manner, inside of the "P."

 

IMG_2381.jpg

 

Here's one from an M1928A1 Thompson.

 

Screen Shot 2019-01-12 at 2.28.12 PM.png

 

Any information you can provide is appreciated. Thanks!

 

David Albert

dalbert@sturmgewehr.com

 

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David, I take a look in my books for any reference on the receiver punch mark. I will say that based on the left of center location for the receiver punch mark I feel pretty confident saying both of the receivers pictured were manufactured at the AOC Bridgeport plant. Savage manufactured receivers have the punch mark centered on top of the receiver nose.

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I may have misunderstood the question, but that mark is the indentation caused when a Rockwell hardness test is performed on a metal (typically to verify that heat treatment brought the steel to the desired hardness), and can be seen on many small arms of the era. The test is still used in industry today.

Edited by NavyEngineer
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I have never read anything specific about these marks pertaining to Thompsons. However,

during the time that the Thompsons were made and serviced it was a standard procedure to put

a prick punch mark on a receiver whenever the receiver was rebarrelled. It is NOT a mark caused

by a hardness tester. A Rockwell tester leaves a tiny mark as seen on the photo of the bolt above,

not a deep recess as seen on the receivers and barrels. The Rockwell B scale uses a 1/16" ball

penetrator. The C scale uses a pointed diamond penetrator. So the punch mark is too deep and

not rounded to be the B scale, and far too deep (again, see tiny marks on bolt) to be the C scale.

All spare Thompson barrels were proof fired and marked with a P at top dead center. I assume

that when a gun was rebarrelled it was proof fired and center punched in the middle of the P and

also the top front of the receiver right behind the P.

How long this procedure was followed I do not know. I think it got its start with the M1903

Springfiled rifles which were in service for over 20 years, many of which had several barrels

fitted over time as evidenced by multiple punch marks on the right side of the front receiver

ring below the serial number.

 

Bob

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IMG_3448.thumb.JPG.9413733e4d6863f15f6984b943d10fb8.jpgIMG_1797.jpg

 

I certainly don't know the origin of the punch marks, but in addition to the AOC Bridgeport M1, I also have a Savage 1928A1 that some have thought might have the original barrel. That gun also has British marks on it possibly indicating Lend Lease/ British service. And, it too has the punch mark on the receive and barrel. FWIW.

Edited by av8tr
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David,

 

What do the rivetson the rear sight look like? Are they flat or do they have a dimple?

 

Just testing a theory.

 

Dan

Bright. Domed on the top; flat on the bottom.

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David,

 

What do the rivetson the rear sight look like? Are they flat or do they have a dimple?

 

Just testing a theory.

 

Dan

Bright. Domed on the top; flat on the bottom.

Please post a picture of that. What manufacturer?

 

I was actually asking David about his AOC guns.

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I have never read anything specific about these marks pertaining to Thompsons. However,

during the time that the Thompsons were made and serviced it was a standard procedure to put

a prick punch mark on a receiver whenever the receiver was rebarrelled. It is NOT a mark caused

by a hardness tester. A Rockwell tester leaves a tiny mark as seen on the photo of the bolt above,

not a deep recess as seen on the receivers and barrels. The Rockwell B scale uses a 1/16" ball

penetrator. The C scale uses a pointed diamond penetrator. So the punch mark is too deep and

not rounded to be the B scale, and far too deep (again, see tiny marks on bolt) to be the C scale.

All spare Thompson barrels were proof fired and marked with a P at top dead center. I assume

that when a gun was rebarrelled it was proof fired and center punched in the middle of the P and

also the top front of the receiver right behind the P.

How long this procedure was followed I do not know. I think it got its start with the M1903

Springfiled rifles which were in service for over 20 years, many of which had several barrels

fitted over time as evidenced by multiple punch marks on the right side of the front receiver

ring below the serial number.

 

Bob

Bob,

 

I was hoping you would see this, and provide your insight. It makes complete sense. Thank you for your post.

 

David Albert

dalbert@sturmgewehr.com

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I have never read anything specific about these marks pertaining to Thompsons. However,

during the time that the Thompsons were made and serviced it was a standard procedure to put

a prick punch mark on a receiver whenever the receiver was rebarrelled. It is NOT a mark caused

by a hardness tester. A Rockwell tester leaves a tiny mark as seen on the photo of the bolt above,

not a deep recess as seen on the receivers and barrels. The Rockwell B scale uses a 1/16" ball

penetrator. The C scale uses a pointed diamond penetrator. So the punch mark is too deep and

not rounded to be the B scale, and far too deep (again, see tiny marks on bolt) to be the C scale.

All spare Thompson barrels were proof fired and marked with a P at top dead center. I assume

that when a gun was rebarrelled it was proof fired and center punched in the middle of the P and

also the top front of the receiver right behind the P.

How long this procedure was followed I do not know. I think it got its start with the M1903

Springfiled rifles which were in service for over 20 years, many of which had several barrels

fitted over time as evidenced by multiple punch marks on the right side of the front receiver

ring below the serial number.

 

Bob

Bob, I am subject to being corrected as my sample size isn't large, but I believe that he prick marks on the receiver were placed there at the time of the original manufacture. Savages are pricked in the center and AOC on the left side. Why would there be a difference if it was done at the time of rebarrel. Also, the P with the punch in the middle is typical of original barrels on military guns (I have more experience with Garands). In the case of Thompsons, it appears that the AOC factory used a serif P and the Savage factory used a sans serif P. With respect to the replacement barrels being proofed with a P, you would know better than I; but on the few I have seen , the P was upside down. In other words, the P is readable from the rear of the gun on original barrels and from the muzzle (at least sometimes) on replacement barrels.

 

Has anyone else noticed anything like this?

 

Dan

Edited by DZelenka
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Were the "replacement barrels" screwed into a receiver or fixture, torqued, fired a .45-round down them, then removed? Were they finished after testing?

 

I have seen WW2 TSMG replacement barrels that don't look to have been shot or ever screwed into anything.....Phil

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You raise an interesting point. I thought that when a firearm was manufactured, it was assembled.

then proof fired, then test fired, and marked with a proof mark. I don't remember individual parts such

as bolts and barrels, being proof fired at the time of manufacture and then again when assembled into

a complete firearm.

I do not believe that proof cartridges were available at field service facilities where much rebuilding

and servicing of guns took place so it would make sense for already proofed bolts and barrels to be

available.

I never paid much attention to the punch marks on the receivers even though I have had hundreds

of them pass thru my hands in the course of my work. I don;t know what percentage had the marks.

 

Bob

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My cash-and-carry British Model of 1928 does not have a punch mark on top of the receiver nose,

nor is there a punch mark in the loop of the P mark on the barrel. The only mark on the receiver

nose is the British crown, which also appears on the right side of the receiver in the three o’clock

position and on top of the actuator. The P mark on the barrel collar is upright when viewed from

the buttstock end of the gun. The gun does, however, have ton markings on the barrel out past

the end of the fins, which, as I understand it, were applied when the barrel was proof-tested when

the gun left British service...

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