Whenever someone asks Doug a Thompson question that generates an answer that would probably be of interest to others, the question (perhaps edited) and the answer will be posted here.

 

                                                          Lefty M1/M1A1 Bolt Handle

QUESTION : I am left handed and wish the M1/M1A1 bolt handle had been located on the left side of the gun. Would that have been difficult to do?

ANSWER: I am right handed and I wish the M1/M1A1 bolt handle had been located on the left side of the gun. It seems that only the U.S. Army likes bolt handles on the right side of guns. Most everyone else prefers the bolt handle to be on the left side or on top. In the case of the Thompson, a bolt handle on the right side means the shooter has to release his hold on the pistol grip (for us righties) in order to cock the gun - a real time waster! Since the 1921/8 bolt handle is on top, this problem does not exist on those guns. And, there is no reason the M1/M1A1 bolt handle can not be on the left side of the gun. If there were a bolt handle slot on the left side of the receiver, the bolt handle could be installed out the left side with no other changes. As a matter of fact, at least one M1/M1A1 gun was manufactured with bolt handle slots on both sides of the receiver. I assume it was made to demonstrate the possibilities. In any case, the decision was made to locate the handle on the right side. I have addressed this problem by offering my M1/M1A1/M2 style Display (TM) receivers with the bolt handle slot(s) anywhere the buyer wants it (them).
 

 

                                                                       Bent Actuators

QUESTION : I have seen actuators which are bent in the lock slot area. Is there any way to prevent that from happening?

ANSWER: This problem is usually caused by a worn lock which enables the actuator to go too far forward in the bolt so as to be stopped by the hammer. The actuator then rides up on the hammer causing it to bend. The solution is to check the bottom front edge of the actuator for a wear spot in the center. If the bluing is worn, it is a sure sign that the lock is worn and actuator damage is coming.
 

 

 

                                                              TSMG Barrel On N/K Gun

QUESTION : What is involved in changing the standard 16" barrel to a TSMG barrel on a Numrich/Kahr gun, assuming that the proper paperwork and tax payment has been completed?

ANSWER: The N/K gun differs from the TSMG in several areas that involve the barrel. The N/K barrel has a smaller diameter and a different profile than the TSMG barrel. The undersized diameter causes problems when using my barrel wrenches and so it must be either removed by holding it in a vise between wood blocks or wrapped with card stock to increase the diameter. The different profile and N/K 3/4" wide grip mount means that the grip mount and forearm/grip must be replaced with Thompson parts. Since the compensator is fixed to the barrel with adhesive and not pinned, it may be necessary to heat the compensator to break the adhesive. If a ring sight is fitted, it may have to be replaced with a TSMG sight as it may not fit properly on the TSMG barrel. Otherwise, standard Thompson barreling procedures should be followed.
 

 

                                  Interchanging Thompson Rear Sights

QUESTION : Can one style of Thompson rear sight be interchanged with another.

ANSWER: Yes. All Thompson rear sights are interchangeable. They are all located in the same place on all models of Thompson guns, have exactly the same hole pattern and use the same special Thompson rear sight rivets. The rear sight rivets are installed up through the receiver and then through the sight. Although, the M1/M1A1 receiver is the same width as the Lyman adjustable rear sight, if that sight is installed on an M1/M1A1 receiver, it will appear to overhang on the sides because of the top edge radii of the receiver.
 

 

                                            Make A Machine Gun

QUESTION : I bought a Thompson parts kit and now I want to buy a semi-finished machine gun receiver and have my local machine shop finish the receiver. Where do I go with this?

ANSWER: Probably to jail along with the machinist. Only a holder of a Class 2 manufacturing license can legally make a new machine gun. I am not an authority on the paper work required. The Small Arms Review magazine deals with the whole area of machine gun manufacturing and sales so that might be a good place to get information.

                                                            Gun Info

QUESTION : I bought a 1928 Thompson parts kit with serial number XXXXXX. Can you tell me who made the gun and when?

ANSWER: If it is a 1928, it was probably made in 1941. If it is a 1928A1, it was probably made in 1942 or 1943. If the barrel is not finned, it would be one of the last ones made. Both Savage and Auto-Ordnance made the guns with Savage prefixing their serial numbers with ”S” and Auto-Ordnance prefixing with “A.O.”. I know of no records being available which would provide more information.

 

                                                   RECEIVER STEEL

QUESTION : Unfinished receivers are being offered in many kinds of steel. What type is best?

ANSWER: Occasionally I get a call asking what type of steel I use to make my receivers. I get interested because I think we are about to have a discussion about metallurgy so I will usually ask what type of steel the caller would prefer. The response I usually get is that the caller knows nothing about steel types. That makes me wonder why the question was asked and the question is answered in my catalog anyway.

But the question asked here is different. When an engineer selects a steel alloy to use to make a product, there are several things to consider including strength, machinability, availability and cost. Strength is determined by the steel’s ability to be hardened. The ability to be hardened and the characteristics of the hardened steel are determined by the alloying elements added to the iron to make the steel. Steel can be machined in its annealed (soft) state and heat treated later or machined in it’s hardened state to begin with. The trade off is that heat treating steel to harden it shocks the steel and always ends up with some distortion. Thompson receivers were originally made from several types of steels which became obsolete over the years. The last Thompson receivers were made from type1141 and then heat treated. Any steel that meets the Thompson specifications for strength can be used but keep in mind that strength is not the only factor. Will the receiver twist during subsequent machining operations? Will it be a problem to machine additional features? Has it been stress relived or is it like a coiled spring ready to move when surrounding metal is removed? So, “best” can be argued. I believe that they selected the best steel alloy and strength originally and that millions of guns used in WW2 proved it. The only change I make is to machine the receivers from the steel in it’s hardened but stress relieved state so there is no subsequent heat treating to cause it to twist during heat treating or during subsequent machining.

 

                                                                   Firing Pin Springs

QUESTION : Are the firing pin springs identical for all models of TSMGs?

ANSWER: Models 1921, 1928 and M1 TSMGs all have separate firing pins using a firing pin spring. The Model M1A1 does not have a separate firing pin and so does not use a firing pin spring. TSMG firing pin springs are identical except that the 1921 spring is 2 coils longer than the 1928/M1 spring. However, a 1928/M1 spring will work and fit in a 1921 gun.
 

                                              1921 Serial #1

QUESTION : Does any one know where 1921 Colt Thompson serial #1 is?

ANSWER: There never was a serial #1 or for that matter serial #2 through 40. Colt never contracted with the Auto-Ordnance Corp. to manufacture 15,000 Model 1921 Thompson guns. Colt did contract to make 15,000 Model 1919 Thompson guns starting with serial number 41 to pick up where Auto-Ordnance left off with their own production. Colt serial #41 was, in fact, a Model1919, but that gun was immediately modified and reconfigured to such an extent that the model name was changed to 1921. So the first Model 1921 gun was serial number 41. The mystery is why Colt didn’t mark the next 40 guns #1 through 40 so that the serial number range would have started at #1.

                                           Interchanging Barrels

QUESTION : I tried to install a used barrel with front sight on a new receiver and the sight did not end up in the vertical position. What is wrong?

ANSWER: Nothing is wrong. Thompsons do not have a qualified thread (also called ordnance thread) which is typical of most guns. The front sight is installed after the barrel has been installed. There is no reason to assume that another receiver will have exactly the same thread position because there is no specification for it. This is probably the biggest problem encountered by persons trying to use a parts kit with a new receiver. Unfortunately, because of the coarse pitch of the barrel thread, it is not possible to further turn the barrel once it is tight. The sight must be moved.
 

                                               Thread Sizes

QUESTION : What is the correct thread size for all the threaded Thompson parts which appear to be about 1/4" in diameter?

ANSWER: #14-24. #14 is .242" diameter. The Thompson uses the same size thread for everything except the compensator, barrel, buttplate door, buttstock reinforcement, 1927 & 1928 (Colt) sling swivels and adjustable rear sight. This is a thread size that is seldom used today. 1/4" (.250") has become the standard but back in 1920 that was not the case. This does not create any particular problem except when someone assumes the thread is 1/4" and so ruins a part by retapping it oversize. Of course, finding taps and dies in #14 size is difficult.
 

                                                             Sling With Vertical Foregrip

QUESTION : What is the best way to fit a sling to a Thompson with a vertical foregrip?

ANSWER: All Model of 1921 and all Model of 1928 (Savage) guns were made with vertical foregrips. Colt guns had no provision for a sling at all whereas the Savage guns did have a sling swivel on the buttstock. During WW2, the British Commonwealth Countries added a sling swivel to the side of the foregrip in order to fit a sling but this was never a factory fitment. In 1922, Auto-Ordnance introduced the Model of 1922 which had a Springfield style swivel retrofitted to a standard 1921 buttstock. A horizontal forearm was introduced with the 1922 which incorporated the second swivel. The swivel equipped buttstocks must have inspired A-O to come up with a way to fit a second swivel on standard 1921 guns so a sling could be used. In 1922, A-O offered 1921 guns fitted with slings as an option. They offered a barrel band which fitted around the barrel just ahead of the foregrip. Unfortunately, this option must not have been popular because no example (or even a photo) of a factory fitted sling on a 1921 gun is known to exist today. In my catalog, I offer an entire sling system for all Thompson guns that includes sling barrel bands and special sling pilots. How close I came to the 1922 barrel band design is only a guess.
 

 

                                                          1921 v. 1928 Bolts

QUESTION : What is the difference between a 1921 bolt and a 1928 bolt or is there any?

ANSWER: Yes, there is a difference. All 1921 bolts are nickle plated. But so are some 1928 bolts. 1928 WW2 bolts are marked with the manufacturers symbol whereas Colt bolts (1921) are unmarked. The real difference is in the way the inside “U”-shaped edge on the back end of the bolts are radiused. 1921 bolts have a circular countersunk depression that bevels the centers of the three sides of the “U”. That pattern matches the round collar on the metal portion of the 1921 Buffer. 1928 bolts have the entire edge of the “U” radiused just to eliminate sharp edges which has no relationship to the larger and flat collar of the 1928 pilot. 
 

                                                                   Gripmount Styles

QUESTION : How many styles of gripmounts were made and how do they differ?

ANSWER: There are three different styles of gripmounts that were fitted to Thompson guns. The first style was fitted to Models 1919, 1921, 1922, 1923, 1927, 1928 and Colt 1928A1 guns. It is a 1-piece gripmount in that it was machined entirely out of one piece of steel. This gripmount is bent up slightly such that the barrel pushes it downward with considerable force. The reason for stressing it was to create a very rigid mount for the vertical front grip that was originally fitted to all 1919 and Colt guns. When the WW2 production switched from the Savage 1928s made for Great Britain, which had vertical front grips, to the U.S. 1928A1s which were fitted with horizontal forearms, there was no longer a need for the rigidity. That lead to the elimination of the bend and the introduction of the second style of gripmont. In my opinion, the projection at the front end of the gripmount which bears against the barrel should have been eliminated completely. This is because it is the forearm which bears against the barrel as the forearm screw is tightened. As the screw is tightened, it is actually pulling the gripmount away from the barrel such that, in most cases, the gripmount no longer contacts the barrel at all. The third style is referred to as the 3-piece gripmount and fitted to M1A1 guns,. This gripmount consists of a flat bar fitted with a front barrel stud and a rear securing stud. Both studs are actually rivets so the 3-piece gripmount can not be disassembled. This gripmount was a complete disaster. It was supposed to save money but, in fact, it is so weak because of the rear stud hole reducing its strength, that it failed in service. By pulling downward on the sling, it is possible to bend the gripmount. To solve this problem, a strap was designed to go around the barrel and forearm and retro-fitted to many of the guns. Later Army drawings show a fourth style that is similar to the U.S.1928A1 style in that it is a 1-piece design but differs in that the front projection is replaced by simply bending the front end upward. There is no evidence that any of the fourth style were made.

 

                                                             M1: Improvement ??

QUESTION : The M1 Thompson was cheaper and simpler compared to previous models, but was there anything about the gun that was an improvement?

ANSWER: Cheaper and simpler pretty much sums it up. But, yes. There is one improvement that was incorporated in the M1 gun. It is an additional sear slot near the back of the bolt that enables the safety to work when the bolt is closed. On previous models, the safety will only work if the bolt is cocked open. Soldiers during WW2 tended to keep the bolt closed to prevent dirt from entering the breech. If the bolt were closed and the gun were dropped on its butt, it would be possible for the bolt to cycle and fire a cartridge. So, the addition of the closed-bolt-safety-slot was definitely an improvement. Earlier bolts can be modified to incorporate this safety feature. If the guns had been made today, they would probably all be recalled to add it.
 

 

                                           Kinked 1928 Recoil Spring

QUESTION: What is the cause and cure for the kinking of a1928 recoil spring?

ANSWER: I have often said that there is no engineering justification for the existence of the 1928 Thompson gun and that every change made to the 1921 Thompson design in order to create the 1928 degraded the performance and characteristics of the 1921. The major case in point being the 1928 recoil spring and pilot design. The only purpose of the pilot is to hold the spring in place in the space between the rear end of the receiver and the back end of the bolt/actuator. Without the pilot there would be nothing to prevent the spring from looping out at its side and kinking. But the pilot is not long enough to fully guide the spring over the entire space. This is because the pilot can not be made long enough to completely guide the spring and still be able to be installed from the bottom of the receiver. On the 1921 gun, the non-piloted gap was not a problem because the diameter of the recoil spring is greater than the length of the gap and so there are not enough unguided coils to loop out. The 1928 gun design reduced the diameter of the spring and increased its stiffness to the point where it is always on the verge of looping out and kinking and will do so if there is any additional aggravating factor. Assuming that the gun is an original 1928 Thompson, which would eliminate such contributing factors as an oversized pilot hole in the receiver, an undersized diameter and/or length pilot or a buffer that is too thin, then it is only necessary to check that there is a breech oiler and buffer in place. If either of those are missing, the gap is increased. Given that the gun is in specification configuration, the cause of spring kinking is the result of operator error in installing the spring. With the spring and pilot out of the gun, as much of the spring as possible must be forced onto the pilot and then secured in place by a pin pushed between the spring coils and through the hole in the front end of the pilot from the bottom side. A 1928 Recoil Spring Stripping Tool, pin punch or even a nail can be used for this purpose. This will allow the end of the recoil spring to be easily fed into the actuator hole and the pilot (with buffer in place) fitted through the oiler and receiver holes with no possibility of looping and kinking. Once the spring/pilot assembly is in place in the receiver, remove the tool. If this procedure was not previously followed and the spring kinked during installation (or because of any other problem), it should be replaced.

 

                                                        Barrel Removal

QUESTION : How does one remove a Thompson barrel, particularly from a parts kit receiver nose section?

ANSWER: Actually, removing a Thompson barrel is quite easy as long as the barrel is to be scrapped. If the barrel is to be saved, which is invariably the case today, there is just no easy way. The two worst aspects of the Thompson design are the 1 in 10 pitch square barrel threads and the grip mount not being removable without first removing the barrel. There is no excuse for the barrel thread design. It is difficult to manufacture and gage and requires tremendous force to tighten or, especially, loosen the barrel. Although Auto-Ordnance came up with several alternative grip mount designs that enabled the grip mount to be removed without removing the barrel, apparently, none proved to be as good as the one used. The result is that the grip mount is always in the way of trying to remove an already problematic barrel. The best advice I can give is to refer to an article I wrote entitled “Barrel Removal”.

                                                     Barrel Torquing Specification

QUESTION: What is the proper torque requirement when installing a Thompson barrel?

ANSWER: There is no torquing specification that I am aware of and it would not be relevant if there was one. There must have been some figure used at Savage and Auto-Ordnance when the guns were made. It would only make a difference if very powerful and expensive machines were used, and they must have had them. From a practical stand point, it is virtually impossible for an individual to over tighten a Thompson barrel. This is because of two factors. The 1 in 10 pitch of the Thompson square barrel thread does not allow any “tweaking”. The barrel goes from loose to tight in just a few degrees of rotation. The barrel does not get tighter and tighter as is the case with V-threads where the external part (nut) actually expands as the tightening force is increased. If it were possible to measure the torque it would go from 0 to off the scale instantly, making a meaningful measurement unobtainable. The other factor is that it is impossible with reasonably available tools to hold the barrel tight enough to be able to over tighten it. Getting the barrel as tight as possible becomes the goal

                                          Worn Barrels

QUESTION : How does one know if a Thompson barrel is worn out?

ANSWER: When the lands and grooves are no longer distinct, the barrel is worn out. Another indication is that shooting accuracy has fallen off. However, very few Thompson guns will reach the point where the barrel is worn out if military specification barrels are fitted. Unfortunately, most new-made barrels are not made to military specifications, so wear may be more of a problem in the future. A much more likely problem will be bore damage. WW2 guns will often show the affects of corrosive ammunition. This is indicated when the bore appears to be worn (actually eroded) at the breech end rather than over its full length. What is a more worrisome possibility is a ringed or bulged bore caused by defective ammunition. Being a machine gun, a bullet that does not make it out the end of the barrel is immediately follow by more bullets that jam in the barrel, destroying it. At the prices Thompsons are selling for, damaging a barrel becomes a catastrophic loss. Therefore, if a nice condition, all original gun is to be shot, I recommend replacing the barrel assembly so that there is no chance of damaging the original one.

 

                                         Ring Front Sight On Threaded Barrel

QUESTION : Can a standard ring style front sight be installed on a barrel that was threaded for a compensator?

ANSWER: No. The muzzle of a barrel made to accept a ring style front sight is larger, smooth and tapered compared to the straight threads on the muzzle of a barrel made to accept a compensator. It is possible to thread the end of a ring sight barrel to accept a compensator. If a ring sight is put on a threaded barrel, it will not be a tight fit. Of course, it could be welded or epoxied to hold it in place, but that is redesigning the gun. I have had several inquiries about the possibility of making some ring sights threaded like a compensator so there would be interchangeability, and that could be done. The problem is that there is just not enough demand to make such a product viable.

 

                                     Parts Kit Semi-Auto

QUESTION : What is involved in making a semi-auto with my TSMG parts kit?

ANSWER : Unfortunately, to the best of my knowledge, as of this date (Jan. 2007) there is no ATF approved way of making a semi-auto gun from a TSMG parts kit as is done with a number of other machine gun parts kits. The assumption being that the semi-auto gun will have the outside dimensions of the original, look exactly like the original and use most of the original parts including magazines. Numrich Arms designed a semi-auto gun years ago that more or less resembles a Thompson. That gun is now manufactured by Kahr Arms. Neither of these companies has any connection to Col. Thompson’s Auto-Ordnance Corp. that invented, developed and manufactured the Thompson Submachine Gun. The N/K gun is not a true Thompson and not made to the original drawings. Therefore, very few Thompson parts fit it. Without an approved design to modify the TSMG to fire semi-automatically, the only option is to make an N/K gun out of a Thompson. Unless one is willing to spend a lot of money and register the gun as a short-barreled rifle, it is not a cost effective project. (My book, “Thompson New Production Semi-Autos” describes this process.) One is better off just buying the N/K gun. If a detachable buttstock is desired, the most cost effective way of achieving that is to fit one of my kits to the trigger housing. If it is desired to have a receiver that is as true to the original as possible, then one of my MS or 2S receivers can be used. But in the end, it still ends up as an N/K gun design, not a Thompson. I have a design for a proper semi-auto Thompson but no time to pursue it. I know others are working on their versions. Maybe something will come of it.


 

                                Ring Front Sight On Threaded Barrel

QUESTION :  Can a standard ring style front sight be installed on a barrel that was threaded for a compensator?

ANSWER:   No.  The muzzle of a barrel made to accept a ring style front sight is larger, smooth and tapered compared to the straight threads on the muzzle of a barrel made to accept a compensator.  It is possible to thread the end of a ring sight barrel to accept a compensator.  If a ring sight is put on a threaded barrel, it will not be a tight fit.  Of course, it could be welded or epoxied to hold it in place, but that is redesigning the gun.  I have had several inquiries about the possibility of making some ring sights threaded like a compensator so there would be interchangeability, and that could be done.  The problem is that there is just not enough demand to make such a product viable.

                                                ALUMINUM TSMG

QUESTION :  Why was there never a TSMG made of aluminum?

ANSWER: Savage did manufacture a Model of 1928 Aluminum TSMG. It had an aluminum receiver and trigger housing left in the white. The buttstock and grips were brown plastic. All other parts were standard black steel. The WW2 Model of 1928 Thompson guns were made for the British including the aluminum version. But, strangely, since all the guns made previously for the British had vertical foregrips, the aluminum gun was fitted with a horizontal forearm. Unfortunately, the aluminum did not pass British testing. It wore excessively on the magazine slots and the receiver was not strong enough. Only one complete original gun is known to exist today and it belongs to the British Government. Had an aluminum M1 been made, it may well have proven to be acceptable. That is because the back end of the receiver is much stronger than that of a 1928 model. Also, since the model M1 will not accept a drum magazine, the stress a drum puts on the receiver slots would not be a factor

 

                               1921/8 Safety Lever Handle Hole

QUESTION : What is the purpose of the hole in the blade handle on safety levers fitted to 1921. 1928 and early 1928A1 Thompsons?

ANSWER: The only purpose of the hole is to provide an axis for the knurling tool as it traveled around the circumference of the radius at the end of the safety lever. When the knurling was eliminated on late 1928A1 gun production there was no longer a need for the hole. Although the rocker pivot (selector) was also knurled, the knurling did not wrap around the lever to the extent that it did on the safety. Therefore, a different setup was possible for the knurling tool that did not require an axis hole in the lever.

 

                                                M1A1 Bolt Handle Groove

QUESTION : At the center of the shank portion of the M1A1 bolt handle (the part that goes into the bolt) there is a groove which lines up with the recoil spring. Does the groove have something to do with the spring?

ANSWER: No. The groove has nothing to do with the spring. The fact is that the groove has nothing to do with the M1A1 gun at all. The A M1A1 bolt handle@ is really not an M1A1 bolt handle. It is an M1 bolt handle which was carried over for use on the M1A1 probably to avoid having to stock two types of bolt handles. The purpose of the groove on the M1 gun bolt handle is to limit the rearward movement of the hammer. The bolt handle shank groove diameter determines the hammer movement limitation. On the 1921/8 gun, the back of the hammer slot in the bolt provides the hammer stop.

                                  1928 Bolt Ramp

QUESTION : There is a ramp (inclined groove) on the bottom back end of the 1928 bolt. What does it do?

ANSWER: You could also have asked the same question about the projection at the top front of the trip because the answer would be the same - nothing! My guess is that it must have seemed necessary to make sure that the trip was in the downward position as the receiver assembly was mated with the trigger housing assembly because that seems to have been the only possible purpose of the ramp and projection. (i.e., the projection is pushed down as it engages the ramp.) This was a solution to a problem that never existed. Someone must have figured this out during the design of the Model M1 gun because the trip projection was eliminated even though M1 bolts still have the ramp. The trip was further simplified and the ramp eliminated with the introduction of the M1A1 gun. The M1A1 trip is the best design of the three versions. The proof of the uselessness of the projection is that an M1A1 trip can be installed on any model Thompson gun with no effect.
                                       M1A1 v. M1 TSMG RELIABILITY

QUESTION: It is my understanding that the M1A1 TSMG is considered to be more reliable than the M1 because of the elimination of the firing pin, firing pin spring, hammer pin and hammer pin. Is that true?

ANSWER: There is no question that fewer parts to break, wear or foul, usually results in more reliability, but that is a minor factor with the Thompson which never suffered from a reliability problem. The main reason the M1A1 gained increased reliability was that the bolt shank (the cylindrical part of the bolt which actually enters the breech) was made longer which resulted in the bolt being stopped by the back of the cartridge rather than by the front end of the receiver bolt cavity. That coupled with the firing pin being machined into the bolt face, which guarantees penetration of the firing pin into the primer, helped eliminate misfires due to defective cartridges.

                               INTERCHANGING TRIGGER HOUSINGS

QUESTION: I have been told that all TSMG and Numrich/Kahr 1927 type trigger housings are interchangeable on all TSMG and N/K receivers and I have also been told they are not. Please clarify this.

ANSWER: All TSMG trigger housings will fit all TSMG receivers regardless of model. All N/K trigger housings will fit all N/K receivers regardless of model. However, an M1/M1A1 (either TSMG or N/K) trigger housing will not accept a drum magazine unless it is modified. There will also be a mismatch between the rear ends of the receiver and trigger housing when M1/M1A1 and 1921/8 style parts are mixed. An M1/M1A1 TH rear end can be modified to match the rear end of a 1921/8 receiver but a 1921/8 TH can not be modified to match the rear end of an M1/M1A1 receiver. The 1921/8 TH mismatch is, however, hidden underneath the M1/M1A1 receiver and so is not easily seen.

A TSMG TH will not fit a N/K receiver without being modified by cutting a slot across the front. TSMG TH internal components will not fit in a N/K TH and will not work with a N/K bolt assembly. N/K components can be fitted in a TSMG TH with slight modifications. A N/K TH will fit on a TSMG receiver but will not work with the TSMG bolt. Probably no one would want to do that anyway.

 

                                  MODELS  OF 1922 & 1923

QUESTION: I have never seen a reference from the time period mentioning the Model of 1922 designation. I have always thought that the different variations of the few known Model of 1923 Thompsons were only prototype variations of a failed product. Please clarify this.

ANSWER: Neither the Model of 1922 nor the Model of 1923 are known to have been mentioned anywhere in the original documentation. Auto-Ordnance called everything “the Thompson gun” which lumped Model of 1919 and Model of 1921 together. In 1922, A-O tried to boost their meager sales by coming up with something along the lines of the BAR in order to appeal to military organizations. The guns they produced were categorized as “The Thompson Gun - Military Model” with no differentiation between actual models, and of course, did not change the guns original “1921" marking. The gun that was shown in the 1923 Catalog was not called a Model of 1923, but since it appeared in the 1923 Catalog, collectors referred to it as the “Model of 1923". What collectors did not realize was there was another “military” model which came before it. There has only been one vintage photo of it found and it was not a good picture. The only example of the gun was thought to be in the West Point Museum but it is not complete and had been extensively modified toward the style of the 1923. Thompson students, including myself, assumed that it was a tool room prototype of the 1923 and it is. What we all failed to realize was that it was only one of the 1922s that had been made and it had been retained by A-O to use as a basis for the development of the 1923. I initiated a quest to find a 1923 in order to document it completely and reproduce it. I have never found one. What I did discover was that only one was documented to have been made. It never left A-O and was eventually broken up for parts. What I did find was a number of intact1922s but since the common belief was that it did not exist, it had no name. So I named it based on the fact that it had to have been made in 1922 (or possibly into 1923). I also refer to both the 1922 and 1923 as “Thompson Submachine Rifles” in keeping with the nomenclature at the time. Guns that collectors are claiming to be 1923s to enhance their value are nothing more than standard 1921s fitted with left over 1922 barrels.
 

                                A5 BARREL THREADS

QUESTION:   Are the barrel threads on a Numrich/Kahr A5 Thompson Pistol the same as a TSMG?

ANSWER:   Theoretically, they are. But the N/K gun is not a Thompson and so the quality and conformance to Thompson specifications of the threading leaves something to be desired. You did not say what you are intending to do. If your intention is to install a 10½" TSMG barrel on an A5, you must register it as an NFA weapon. Mere possession of an A5 gun and a TSMG barrel would probably be considered to be a violation. The best thing to do with an A5 is to leave it alone and not have any parts around, including an N/K 1927A1 gun, that could be used to assemble an NFA weapon. This confusion is caused by the A5 being marked “pistol” when it is not classified as a pistol by the ATF.

                              COLT SLING SWIVEL

QUESTION:   What would be the correct type of sling swivel on a Colt TSMG?

ANSWER:  Colt never put a sling swivel on a TSMG during the Model of 1921 gun production. In 1922, Auto-Ordnance fitted 1921 Colt buttstocks with 1903 Springfield Rifle swivels for the Model of 1922 Thompson Submachine Rifles. In 1923, entirely new buttstocks designed without any drop at the rear end and newly designed horizontal forearms were made and again fitted with Springfield swivels for fitment on the Models of 1923 Thompson Submachine Rifles. In 1927, 1921 Colt buttstocks and redesigned forearms were fitted with offset, 3-piece Enfield swivels for the “new Colt” Models of 1927, 1928, 1928 Navy and 1928A1. In 1936, A-O went back to using the Springfield swivels. It is interesting that around 1923, A-O offered Model of 1921 guns fitted with slings. This was done by fitting 1922 buttstocks and either 1923 forearms or fitting a sling barrel band in front of the standard vertical foregrip. Unfortunately, there is no known example or even a photo of the sling barrel band. I do offer my own version in my catalog.

                             WW2 TSMG FINISH

QUESTION: Some people claim that WW2 TSMGs were Parkerized and others claim they were black oxided. Which is true?

ANSWER: No TSMG ever left the factory with a Parkerized (phosphate) finish. All WW2 TSMGs were black oxided. The confusion comes from 3 sources. Mostly, people don’t know what they are talking about. But, a lot of guns were refinished (not by the U.S. Army) with a phosphate finish because it hides a lot of imperfections and it is more durable than black oxide. The last source of the confusion comes from the U.S. Army. All the Thompson drawings were redone in the 1950's by the Army and those revised drawings specify phosphate. So, if the Army were to put the Thompson back into production, the new guns would be phosphated. However, the Army seems to have lost all the Thompson drawings and they never liked the Thompson anyway.

                         M1 & M1A1 TRIGGER HOUSING SERIAL NUMBERING

QUESTION: Are all M1 & M1A1 trigger housings serial numbered?

ANSWER: M1 and M1A1 trigger housings made by Savage are serial numbered on the bottom of the trigger guard whereas the ones made by Auto-Ordnance are not serial numbered. However, sometimes new serial numbers were stamped on for various reasons by military depots, etc., which confuses the issue. Those numbers are usually recognizable by their placement or crudeness.

                        VERTICAL FOREGRIP BOLT SLING SWIVEL

QUESTION:  Did Auto-Ordnance ever make a vertical foregrip screw with a sling swivel on the end? I have seen one like that.

ANSWER:  No. Things like that are aftermarket creations by some individual or sometimes they are movie props. I am located in the vicinity of several movie prop shops which are prolific at coming up with novel Thompson ideas that look great on the screen but would never hold up in real service like quick detachable barrels, folding stocks and quick removable gripmounts. In this case, I can’t imagine how such a sling swivel could work. Interestingly, someone wrote an article about a “rare” Thompson barrel that he had found at a gun show. It accepted a Sionics silencer. It turned out that it was something I had made and offered years ago in an old catalog. What amazed me was all the speculation and assumptions that were made about it as to its probable Thompson history. It had no history.

                      1928 & M1/M1A1 RECOIL SPRINGS

QUESTION:  The 1928 recoil spring is U.S. Army part number A153024. The M1 and M1A1 recoil spring is A153116. But, I am told the 1928 gun and M1/M1A1 guns use the same recoil spring. How can this be?

ANSWER:  Spring A153024 is identical with spring A153116 so, the answer is that the 1928 gun and M1/M1A1 guns use the same spring. This confusion is caused by the Army using the drawing number as the part number. The part is the same but the application (spring loading, etc) is different for the different guns. The application specifications require different drawings even though the part is the same. The problem comes at the depot level when someone needs a replacement spring for a 1928 gun but all they have are spare springs for the M1 and M1A1 guns. The box for the 1928 springs is empty. How is the parts guy supposed to know they are the same if the part numbers are different? Drawings are engineering tools. Part numbers are assembly tools. The two should not be mixed. Fortunately, this is the only Thompson part that I can think of where this situation exists.

                       TSMG WON’T FIRE IN SEMI-AUTO

QUESTION:  When I fire my Thompson in full-auto, it works perfectly. But, when I switch to semi-auto, it fires once and then the trigger remains jammed in the rear (pulled) position. If I pry the trigger forward into its normal position, the gun will again fire once with the same result. What’s wrong with my gun?

ANSWER: This problem is caused by dirt and/or bad or wrong spring(s). It would seem that it is time for that 50 year service on your Thompson. Disassemble your gun and remove and break down all trigger housing components. Clean out all spring holes with twist drills the same size as the holes. Clean everything with gasoline. Check and replace all springs as needed. Reinstall all springs making sure they bottom out in the holes and don’t interchange the disconnector and sear springs. Reassemble the trigger housing. Lightly oil the components. Check for correct operation of the trigger hosing assembly. Reassemble the gun. Repeat this procedure in 50 more years. In the meantime, don’t mess with the gun. It was taking the trigger housing apart that probably caused your problem in the first place. A quick gasoline wash and light oil once in a while without disassembling the trigger housing is usually all the maintenance ever required.

                    REAR GRIP LOCK WASHER

QUESTION:  Every WW2 TSMG I have taken apart has a lock washer under the rear grip bolt but I can’t find a reference to that part on any drawing, manual or parts list. What is the story on that?

ANSWER:  You are right and I don’t have an answer for you. I have always felt that the 7/16" diameter grip bolt head was too small to be properly supported by the grip wood. I think they should have used ½" diameter heads like those on the buttstock. When the Model of 1919 was redesigned to include a buttstock, Colt (or someone) had the smarts to use a larger bolt head. Very likely, the lock washers were field installed out of standard military hardware stock to act as a spacer to prevent the bolt from going too far into the trigger housing parts cavity as it was retightened.
 

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