dalbert Posted January 12, 2019 Report Share Posted January 12, 2019 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." Here's one from an M1928A1 Thompson. Any information you can provide is appreciated. Thanks! David Albertdalbert@sturmgewehr.com Link to comment Share on other sites More sharing options...
bob241 Posted January 12, 2019 Report Share Posted January 12, 2019 I think these markings are stamped on the gun when it was proofed . see below form. http://www.machinegunboards.com/forums/index.php?showtopic=13868 Link to comment Share on other sites More sharing options...
Bridgeport28A1 Posted January 12, 2019 Report Share Posted January 12, 2019 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. Link to comment Share on other sites More sharing options...
av8tr Posted January 12, 2019 Report Share Posted January 12, 2019 I agree with both responses above. My AOC M1 is marked/punched exactly like the M1A1 pictured above, to include the AOC mark on the barrel. Link to comment Share on other sites More sharing options...
dalbert Posted January 13, 2019 Author Report Share Posted January 13, 2019 Both of these are AOC Bridgeport. David Link to comment Share on other sites More sharing options...
NavyEngineer Posted January 13, 2019 Report Share Posted January 13, 2019 (edited) 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 January 13, 2019 by NavyEngineer Link to comment Share on other sites More sharing options...
giantpanda4 Posted January 13, 2019 Report Share Posted January 13, 2019 I also would say Rockwell B hardness test mark. Link to comment Share on other sites More sharing options...
NavyEngineer Posted January 13, 2019 Report Share Posted January 13, 2019 I also would say Rockwell B hardness test mark.Exactly! Link to comment Share on other sites More sharing options...
Adg105200 Posted January 14, 2019 Report Share Posted January 14, 2019 Very interesting! I learned something new today Andrew Link to comment Share on other sites More sharing options...
TSMGguy Posted January 15, 2019 Report Share Posted January 15, 2019 My M1928A1 has this mark. The gun is in original 99% of new condition, matching, never refinshed and never diassassembled past field strip. Link to comment Share on other sites More sharing options...
Bridgeport28A1 Posted January 15, 2019 Report Share Posted January 15, 2019 Not one, not two, but three Rockwell B Hardness Tests the underside of this 1928 AOC bolt. Link to comment Share on other sites More sharing options...
DZelenka Posted January 16, 2019 Report Share Posted January 16, 2019 David, What do the rivetson the rear sight look like? Are they flat or do they have a dimple? Just testing a theory. Dan Link to comment Share on other sites More sharing options...
john Posted January 17, 2019 Report Share Posted January 17, 2019 US 1928 A1, S-541xxx, possibly original barrel? (My new '28 Savage) Link to comment Share on other sites More sharing options...
reconbob Posted January 17, 2019 Report Share Posted January 17, 2019 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 puta prick punch mark on a receiver whenever the receiver was rebarrelled. It is NOT a mark causedby 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" ballpenetrator. The C scale uses a pointed diamond penetrator. So the punch mark is too deep andnot 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 assumethat when a gun was rebarrelled it was proof fired and center punched in the middle of the P andalso 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 barrelsfitted over time as evidenced by multiple punch marks on the right side of the front receiverring below the serial number. Bob 1 Link to comment Share on other sites More sharing options...
av8tr Posted January 17, 2019 Report Share Posted January 17, 2019 (edited) 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 January 17, 2019 by av8tr 1 Link to comment Share on other sites More sharing options...
TSMGguy Posted January 17, 2019 Report Share Posted January 17, 2019 David, What do the rivetson the rear sight look like? Are they flat or do they have a dimple? Just testing a theory. DanBright. Domed on the top; flat on the bottom. Link to comment Share on other sites More sharing options...
DZelenka Posted January 17, 2019 Report Share Posted January 17, 2019 David, What do the rivetson the rear sight look like? Are they flat or do they have a dimple? Just testing a theory. DanBright. 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. Link to comment Share on other sites More sharing options...
dalbert Posted January 17, 2019 Author Report Share Posted January 17, 2019 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 puta prick punch mark on a receiver whenever the receiver was rebarrelled. It is NOT a mark causedby 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" ballpenetrator. The C scale uses a pointed diamond penetrator. So the punch mark is too deep andnot 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 assumethat when a gun was rebarrelled it was proof fired and center punched in the middle of the P andalso 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 barrelsfitted over time as evidenced by multiple punch marks on the right side of the front receiverring below the serial number. BobBob, I was hoping you would see this, and provide your insight. It makes complete sense. Thank you for your post. David Albertdalbert@sturmgewehr.com Link to comment Share on other sites More sharing options...
DZelenka Posted January 17, 2019 Report Share Posted January 17, 2019 (edited) 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 puta prick punch mark on a receiver whenever the receiver was rebarrelled. It is NOT a mark causedby 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" ballpenetrator. The C scale uses a pointed diamond penetrator. So the punch mark is too deep andnot 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 assumethat when a gun was rebarrelled it was proof fired and center punched in the middle of the P andalso 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 barrelsfitted over time as evidenced by multiple punch marks on the right side of the front receiverring below the serial number. BobBob, 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 January 17, 2019 by DZelenka Link to comment Share on other sites More sharing options...
anjong-ni Posted January 18, 2019 Report Share Posted January 18, 2019 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 Link to comment Share on other sites More sharing options...
reconbob Posted January 18, 2019 Report Share Posted January 18, 2019 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 suchas bolts and barrels, being proof fired at the time of manufacture and then again when assembled intoa complete firearm. I do not believe that proof cartridges were available at field service facilities where much rebuildingand servicing of guns took place so it would make sense for already proofed bolts and barrels to beavailable. I never paid much attention to the punch marks on the receivers even though I have had hundredsof them pass thru my hands in the course of my work. I don;t know what percentage had the marks. Bob 1 Link to comment Share on other sites More sharing options...
Speeddemon02 Posted January 18, 2019 Report Share Posted January 18, 2019 Are there guns that do not have these marks that were not refinished that might cover them up? Link to comment Share on other sites More sharing options...
DZelenka Posted January 18, 2019 Report Share Posted January 18, 2019 Are there guns that do not have these marks that were not refinished that might cover them up?Does anyone have a military Thompson without the punch mark on the top of the receiver nose? Link to comment Share on other sites More sharing options...
Jack Wright Posted January 18, 2019 Report Share Posted January 18, 2019 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 receivernose is the British crown, which also appears on the right side of the receiver in the three o’clockposition 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 pastthe end of the fins, which, as I understand it, were applied when the barrel was proof-tested whenthe gun left British service... Link to comment Share on other sites More sharing options...
anjong-ni Posted January 19, 2019 Report Share Posted January 19, 2019 There's probably a "Thompson" in there somewhere.....Phil Link to comment Share on other sites More sharing options...
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