stingray656667 Posted December 29, 2018 Report Share Posted December 29, 2018 Hello, I'm a new member to the board and happy to have a wealth of information available through this site. I've been looking at acquiring a Thompson M1 or M1A1 kit as I recently got interested in them. I've come across one that is a Savage produced lower that has a rectangular recess machined into the lower receiver behind the fire control group and above the shoulder stock screws. I haven't seen this before and I was wondering what the purpose of this recess is. Can any of the members shed some light on this machined recess? Thank you very much and may you all have a safe, healthy and Happy New Year! Joe Link to comment Share on other sites More sharing options...
ppgcowboy Posted December 29, 2018 Report Share Posted December 29, 2018 Can you post a picture? Link to comment Share on other sites More sharing options...
gijive Posted December 29, 2018 Report Share Posted December 29, 2018 stingray656667, Not sure what you are referring to? I have posted some pictures to help you describe what you are referring to. 1 Link to comment Share on other sites More sharing options...
stingray656667 Posted December 30, 2018 Author Report Share Posted December 30, 2018 Hello, I've looked at this kit but I didn't have the foresight to take a picture of the machined recess that I'm trying to describe. The recess is on the top side of the lower receiver, not the bottom side where the trigger, guard and the vertical grip are located. The recess is located on the top surface of the lower receiver where the bottom side of the bolt would ride. I vaguely remember coming across a seller who had a parts kit for sale with this recess machined into the lower receiver. I'll try to find their website and post it for the members to see if the kit is still listed. Thank you very much for the replies. Joe Link to comment Share on other sites More sharing options...
Bridgeport28A1 Posted December 30, 2018 Report Share Posted December 30, 2018 Recess may be where the later pinned stock mounting boss was machined. Link to comment Share on other sites More sharing options...
mohawk64 Posted December 30, 2018 Report Share Posted December 30, 2018 I had a very early west Hurley M16. It had a rectangular slot in that are. Best I can remember it was about 2 inches long. Link to comment Share on other sites More sharing options...
mohawk64 Posted December 30, 2018 Report Share Posted December 30, 2018 M1. Not M16 Link to comment Share on other sites More sharing options...
stingray656667 Posted December 30, 2018 Author Report Share Posted December 30, 2018 Hello, I couldn't find the original item I found for sale online but I did find one on Gunbroker that has a photo of the machined recess that I'm referring to. The item number on Gunbroker is 793572809 photo #9. It shows the recess that I'm talking about quite clearly. Thank you very much for the replies received. I hope this helps determine what this rectangular recess is. Happy New Year to all ! Joe Link to comment Share on other sites More sharing options...
Bridgeport28A1 Posted December 30, 2018 Report Share Posted December 30, 2018 (edited) Hello, I couldn't find the original item I found for sale online but I did find one on Gunbroker that has a photo of the machined recess that I'm referring to. The item number on Gunbroker is 793572809 photo #9. It shows the recess that I'm talking about quite clearly. Thank you very much for the replies received. I hope this helps determine what this rectangular recess is. Happy New Year to all ! JoeJoe, In the photo you reference I believe the rectangular recess is where the pinned mounting boss for the long stock mounting screw was machined on the top. Edited December 30, 2018 by Bridgeport28A1 Link to comment Share on other sites More sharing options...
ppgcowboy Posted December 30, 2018 Report Share Posted December 30, 2018 (edited) M1. Not M16You can edit the post using the edit button. Edited December 30, 2018 by ppgcowboy Link to comment Share on other sites More sharing options...
stingray656667 Posted December 30, 2018 Author Report Share Posted December 30, 2018 Hello, By pinned stock, do you mean the circular boss on the underside of the receiver that fits into the large hole in the shoulder stock? The stock is still held in place by two machine screws isn't it? There's a photo posted by gijive that shows the circular mounting boss on the underside of the receiver closest to the trigger and guard. I don't understand why some of the lowers that I've seen do not have this machined area whereas a small amount of them do yet they all have the circular mounting boss on the underside of the receiver for the front attachment point of the shoulder stock. I sincerely appreciate all of the replies posted. Thank you very much. Joe Link to comment Share on other sites More sharing options...
gijive Posted December 30, 2018 Report Share Posted December 30, 2018 (edited) Hello, By pinned stock, do you mean the circular boss on the underside of the receiver that fits into the large hole in the shoulder stock? The stock is still held in place by two machine screws isn't it? There's a photo posted by gijive that shows the circular mounting boss on the underside of the receiver closest to the trigger and guard. I don't understand why some of the lowers that I've seen do not have this machined area whereas a small amount of them do yet they all have the circular mounting boss on the underside of the receiver for the front attachment point of the shoulder stock. I sincerely appreciate all of the replies posted. Thank you very much. JoeJoe, Okay, I understand what you mean now. Originally, all the Thompson Grip Frames were milled out of a solid piece of steel. Later, Savage developed a means of reducing machining steps by making the "boss" (The threaded piece for the shorter buttstock screw) a separate piece and pinning it to the grip frame. The recessed mark you refer to was apparently a final grinding step to ensure the rearward bolt travel would smoothly travel over the pinned boss. This procedure is explained in "American Thunder III" by Frank Iannamico. I suggest you try and obtain a copy. It is an excellent reference on the WWII Thompson guns. Edited January 4, 2019 by gijive 1 Link to comment Share on other sites More sharing options...
stingray656667 Posted December 30, 2018 Author Report Share Posted December 30, 2018 Hello, Thank you very much for enlightening me with regard to this machining and pinning process. I've realize that as the Thompson moved along in the production process modifications and design changes were effected to decrease production time by simplifying the design of the weapon, however, I had not heard of nor had I seen this particular modification before. I will search out the publication you mentioned and obtain a copy for future reference. Thank you gijive and all those who responded to my inquiry. Happy New Year to all! Joe Link to comment Share on other sites More sharing options...
Adg105200 Posted January 1, 2019 Report Share Posted January 1, 2019 It is very interesting to see all the variations during the production of Thompsons. The change in machining vs a separate pinned boss is something I have noticed before and is mentioned in another topic (can't remember which one). I've just never really been able to quite narrow down when exactly the switch was made but I see the serial number on the above mentioned listing is 116,276. For reference here is a picture of S10574 Does anyone know or have pictures of what AOC did? Did they always pin their boss on? Interesting stuff! Andrew Link to comment Share on other sites More sharing options...
stingray656667 Posted January 1, 2019 Author Report Share Posted January 1, 2019 Good Morning and Happy New Year to All! Thank you for the replies and photos from which I now understand what the pinned version of the Savage lower refers to. I have a clear understanding of the cost saving machining process which produced the rectangular recess that I was wondering about. I've yet to come across a AOC lower so I'm not certain if they were doing things the same way as Savage was. I am still looking for an M1 or M1A1 kit since most of the ones I've looked at seem as though they've really been through the ringer. If any of the members have or know of such a kit for sale, please let me know as I am an interested party for the right kit. I've been looking on the usual sources, Gunbroker, Sturmgewehr etc., but the ones that are out there seem quite expensive and they are not in the condition that I'm looking for. Ebay has even sold one or two in the last month or so. Thank you for the education and Happy Holidays! Joe Link to comment Share on other sites More sharing options...
gijive Posted January 1, 2019 Report Share Posted January 1, 2019 Below are some additional reference photos of a different Savage Grip Frame with the milled "boss". This one is a little "worse for wear", but gives you an idea of the difference in the machining process. Link to comment Share on other sites More sharing options...
Adg105200 Posted January 1, 2019 Report Share Posted January 1, 2019 Here are a few more to add to the list. I wonder what the real time and cost difference it was for them to switch to anone piece machined later in production. I would have thought pinning on the boss would have been faster and cheaper, but that's what was done in the early production stage. I have M1 trigger frames 161,349 (pinned) and 203,072 (machined) so the switch must have been made somewhere in between. 203,072(machined): 161,349(pinned): Anyone else have any with numbers in between these so we could maybe narrow the switch down a little more, or have one before that is machined or after that is pinned?Of course there could also be later production blank(no serial #) trigger frames that were numbered later in the war or during a rebuild and paired with a early # receiver. Andrew Link to comment Share on other sites More sharing options...
full auto 45 Posted January 1, 2019 Report Share Posted January 1, 2019 I have some M1/A1 lowers. None have the mark like yours does. I have another somewhere , when I find it I'll post it.Sorry the pics are sideways, they came off the phone. Gun #511626 "Band of Brothers" signed lower Turkish Lower Rough Lower Link to comment Share on other sites More sharing options...
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