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The Thompson 1927

Length Overall Barrel Length Weight  Caliber Action Type Magazine capacity
41 Inches
16.5 Inches
13 pounds (w 30 round stick)
.45 A.C.P.
Recoil Semi

The Legendary Thompson
Personal Observations
It's all a Matter of Details
Stick Magazines
Installing The Thompson Drum
Loading the Drum
Thompson Drums
Cleaning the Thompson
Thompson Links
The Legendary Thompson
   Suppose you had an opportunity to purchase a 45 A.C.P. firearm which weighs 13 pounds, is over 40 inches long, and costs over $1000. You might laugh, particularly if you were told that the weapon in question was limited to ten rounds. Well, this is a technical description of the Thompson, at least in it's civilian legal form. The magazine ban has, happily, ended, and the gun is now available with thirty and fifty round magazines. Even so, with a fifty round drum, which adds another 4.75 pounds to the total weight, this makes for a very heavy, and rather cumbersome 45 caliber firearm, by today's standards. Compared to today's Ingrams, AR-15s, AUGs, and HKs, the Thompson seems to be eminently impractical, not to mention quite expensive. Still, judging this firearm by it's specs, and by the performance of it's cartridge, ignores one of the most important fields by which any civilian firearm is judged; this is the "neat" factor. If there is one thing that the Thompson has in abundance, its "neat".
      The Thompson has several distinctions, which add greatly to the "neat" factor. The strongest may be the historical factor. Though designed for use in the trenches of the First World War, the gun made it into production too late. Still, it was to have many chances to distinguish itself latter. This was the first  American submachine gun, and the first relatively handy fully automatic arm. It was also made famous by numerous television shows, movies, and by it's actual role as a favored weapon of many high profile men on both sides of the law. The infamous Thompson was part of the catalyst which helped pass the odious NFA of 1934, outlawing fully automatic arms for mere subjects of the government. There is also the look of the gun. The vertical grip of the Thompson has been widely copied, and this, along with the drum magazine, and the top mounted cocking lever, give this gun a unique style. Then there is the quality of manufacture.
    These guns are wonderfully made, in the classic tradition. A Thompson is a heavy solid gun, made from wood, and machined steel (aluminum versions are now available), finely blued (in the case of the M1927), and well crafted. Compared to the stamped and riveted construction of today's military weapons, the Thompson is a class act. General Thompson designed this gun in a world full of craftsmen and machinists. This rare example of an old world design for the new concept in modern battlefields was relegated into secondary status around the middle of World War Two. Even so, it was a common weapon in Korea, and was often seen even as late as the Veit Nam War.
    This particular example is the deluxe 1927 model. This model features a finned barrel, a leaf sight which is adjustable for extreme range, and a Cutts Compensator. This classic version of the Chicago  Typewriter also has the horizontal foregrip, and takes the venerable Thompson drum magazine. The original 1927 model was essentially a semi auto version of the famous 1928 model, and fired from an open bolt. The current model has some internal changes, needed to make this gun more difficult to convert to full auto. This is also the model with the top mounted cocking lever, as opposed to having it located on the right side of the receiver as in the  M1. The 1927 model is semi auto only, and fires from a closed bolt.
    There have been four different design capacities for the famous Thompson drum magazine. All will fit only the 1927,1928 models, but not the latter M1 designs. The first, and most famous, is the venerable 50 round magazine. This was followed by a much larger, and heavier 100 round magazine. This in turn was followed by a 39 round drum. Then there was the sad 10 round magazine, mandated by the useless and unconstitutional magazine ban. These are all classic, first generation style metal drum magazines. They are spring wound, using a removable key, and employing coil springs, and a metal spider to advance the cartridges. 
    The original fully automatic Thompson submachine guns had 10 to 11.5 inch barrels. Unfortunately, Roosevelt determined (via the NFA of 1934) that we were not to be trusted with short barreled long guns, nor were we to be trusted with fully automatic firearms. So the civilian legal version has a 16.5" barrel. This actually gives it a somewhat more graceful look, as compared to it's stubby war bred brethren. There is probably some small ballistic advantage to the slightly longer barrel, though I suspect it may be very slight. A 230gr bullet which leaves the 5" barrel of a standard 45 pistol at 842 fps, will exit the Thompson's 16.5" barrel at 1092 fps. I would imaging that out of a 10.5" barrel, velocity  attainedis on the order of 950 - 1000 fps; but I have no gun with which to test this theory. Auto Ordnance is offering shorter barreled semi auto guns, for civilian purchase, but these short barreled guns are covered under the NFA, and must be registered, just like a machine gun.
    The standard civilian legal guns of today also lack the easily detachable stocks of the originals. These guns, in all variations, are quite long, by today's standards, which gives an indication of how remarkable the Uzi, and the rest of the second generation sub machineguns must have seemed at their inception. The chamber of the Thompson is at the point just ahead of the magazine. The magazine, in turn, is forward of the trigger. The spring which drives the bolt, is nearly as long as that of the M-16, and adds about as much length to the rear of the receiver. On the other hand, this lack of space saving features, along with the general excellent production quality of the gun, may be what gives the Thompson it's reputation for dependability. The M-16, M-14, and even the Garrand, all had teething problems of some sort, and required a fair amount of care to keep in working order. The Thompson, except for it's intricate drum magazines, is not quite so fussy.
Personal Observations
    My first impression, upon handling this gun was "My god, this thing is heavy!" I suspect that this is a common observation. The Thompson is also very bulky, and squared off, compared to today's designs. What is really striking, though, is the huge expanse of finely blued metal. Most guns today are parkerized, have a matte finish, or are largely plastic. The Thompson is blued like an oversized pistol. The use of wood furniture, as opposed to today's plastics, also serves to give the gun a unique look. Though it takes a heavy hand to operate the top mounted cocking lever, this is quite an easy gun to fire. It may be the weight, or the effect of the Cutts Compensator, but recoil is negligible. I have shot some pretty amazing one inch groups with this gun, at 50 yards. What makes these group sizes really amazing is that they are made despite a rather heavy trigger pull. I am hoping for the pull to ease up a bit, once the gun is broken in. The leaf sight is wonderful, and is certainly better than the vestigial little notch. The sight probably adds as much to the gun's great accuracy as anything. Taking this gun to the range is a sure fire ego booster. Everyone wants to look at it, shoot it, own it! This is a feeling I can well understand; I have wanted a genuine Thompson for thirty years.
    In case you can't tell, from the length of this page, or from my comments, I am very enthusiastic about this gun. I have wanted one since my teens, and like most boys, thought highly of it as a child. I almost made the purchase several times, in the last ten years or so, but I could not bring myself to take the plunge, while the issue of magazine availability was so uncertain. The costs of these guns skyrocketed, after the ban went into place, but they eventually returned to Earth. The costs of the magazines was another matter. A few years into the ban, magazine prices became a bit more reasonable, at least on the stick magazines. With tens of millions of war surplus sticks out there, a price drop was inevitable. This was not the case with the drums. A Thompson drum magazine cost close to $2000, during the first year or so of the ban. Half way into the ban the price fell to about $1100, and this was pretty much where it strayed, until a year or so before the ban was lifted. With Bush in office, and a fair (but by no means absolute) certainty that the ban would not be renewed, prices dropped to about the $800 level. Still too much, but getting better. Drum magazines are, at this writing, selling for about $400, though the ban has now ended. Auto Ordnance is selling new drums for $284, but is far back ordered. I plan to pick up a pair of new magazines, as soon as I can get them for under $300. The ban ended in mid September, and I picked up my new Thompson in early October. I guess you could say that I figured I had waited long enough.
    The advertisement to the left, was used in the twenties, and harkened back to an America which had, at the time, only just passed. While the cowboy, indian, rancher, and even the rustler still existed, the days of the wild frontier, open range, and of the Wild West had disappeared thirty years before. Though attempting to associate it with the legend of the expanding frontiers, and independent American, the Thompson would latter become a legend in it's own right. The legend that would surround the Thompson would be, not about war, or about the independent American; but about those who would set themselves as being independent of the law, and of those who would oppose them. The Thompson will always be remembered as the gun of the gangster, and the lawman, rather than that of the rancher, and the trench bound soldier. This ad was placed back in the day when anyone could walk into a hardware store, department store, or sport shop, pick out a Thompson, pay for it, and take it home. This was, I hasten to say, a fully automatic Thompson.
    It's hard to justify the purchase of such a gun, by any kind of logic, particularly at the prices these classics are commanding. It sort of reminds me of a firearm version of one of the classic muscle cars of the sixties/seventies, which are now selling for anything from tens of thousands, to millions of dollars. In both cases, you have a machine that is not sophisticated, by today's standards, nor as potent as some of today's top contenders, but there is something reassuring about the classic lines, and performance. Nothing designed today has quite the look or style, and even the performance, still respectable, can sometimes be a bit surprising. It took Detroit thirty years to equal and surpass the performance of the classic muscle cars, and it has never equaled the affordability or exhilaration of those great machines. Much the same can be said of the Thompson. There are still people who argue the merits of the big, heavy Thompson, unsophisticated, and manufactured by forging and milling steel. They compare it to today's stamped, lightweight, sophisticated firearms, and shake their heads. I have read stories of soldiers in Veit Nam carrying Thompsons, and using them to back up their buddies, after malfunctioning M-16 rifles put them in peril. These stories must qualify as the ultimate vindication of a classic design.

It's all a matter of the Details

The original Cutts Compensator was a sort of precursor to the Magna porting, and other recoil control devices in use on today's modern handguns.
An adjustable leaf sight, just like on the original, which folds down to become a standard notch sight. The leaf sight itself is a peep sight which can be adjusted up and down a sort of a ladder. The photo to the right shows the delicate sight folded down out of harms way, while the photo at left shows it raised, for use at longer distances.

The barrel is ribbed, like the original, and the front grip never quite comes in contact with it. The front grip actually fits onto a metal extension of the frame.
The top mounted cocking lever is knurled, and machined with a large U shaped notch to allow use of the sights. This would seem to make the gun somewhat ambidextrous, except for the right side ejection. The cocking lever is a bit hard on the hands. No wonder you always see them wearing gloves in the gangster movies. The knurling, along with the edges of the notch in the center, combine with the very heavy bolt return spring to make quick cocking of this piece a memorable occasion, but one not likely to be repeated.

Using the Thompson Stick magazines.
    Though these guns are forever associated with their drum magazines, it has always been far more common to see a Thompson loaded with a twenty or thirty round stick magazine. This was particularly true after the introduction of the M1 models, during the Second World War. These newly designed models, stripped down for ease of manufacture, were not capable of taking the drum magazines. This was due, in large part, to the cost of the drum magazines, but weight, and the relative fragility of the complicated winding mechanisms were also factors. Millions of M1 Thompsons were manufactured, while the drum capable 1921, and 1928 models numbered only in the thousands.
    The drums could also be quite a chore to load, and maintain, and were fairly difficult to install, particularly in the heat of battle. If the small "Third Hand" used to install the drums was lost, installation could be next to impossible. Drums were also susceptible to denting, overwinding (or lack of winding), and could make the already heavy guns really clumsy to handle.
    The original Thompson stick magazines had a capacity of 20 rounds; for extended firing, the drum magazine was used. When the military redesigned the Thompson for the Second World War, the drums were not considered to be practical. It was also noted that several additional  manufacturing steps were required, to make the guns capable of accepting them. These steps were eliminated from the M1 versions, which served to simplify manufacturing, thus the cut out, and guide slots needed for the drums were deleted from the design. The external magazine latch was also deleted.
    To partially make up for the firepower lost by the M1 incompatibility with the old drum magazines, newly designed stick magazines, introduced in 1942, now had a capacity of 30 rounds. One unique characteristic of both types of stick magazine is the inclusion of a vertical rail at the rear of the magazine body. Though this would not have been needed on the M1 versions, had they been designed with a magazine well, it had been a requirement on the old drum capable Thompsons, because of the interference that a magazine well would have caused to installation of the drum. Thus the newly designed stick magazines would fit the previous drum capable models, many of which were in use by U.S. forces at the time. It would also be possible to use the stock piles of existing Thompson sticks, without modification in the new M1 models. This course was not followed with the introduction of the Thompson's successor, the M-3 "Grease Gun". The M-3 had a magazine well, and used single track magazines, which were much simpler, and easier to manufacture. The comparatively crude, and primitive M-3 never inspired the kind of admiration or cultishness that was lavished upon the Thompson.
    The Thompson stick magazines are of the double column type, much like a modern high capacity pistol magazine; but they require no magazine well. Unlike most high capacity magazines, which are completely encased in their tight fitting magazine wells, those of the Thompson hang out in the open. They are held in place by a partially enclosed slot milled into the gun's receiver. The rail on the back of the magazine fits up this slot, and guides the magazine into place. A catch within the slot engages a hole in the magazine's guide rail, locking it in place. So the catch is on the back of the magazine, rather than the more familiar side, as in most pistol and assault rifle magazines. These magazines are also substantial, and do not have the throw away design of many contemporary designs.
    I mentioned above that efforts were made to retain compatibility between different magazine styles, and the different Thompson firearms; but this was not always perfect. The modern Thompson expects to find a hole for the magazine catch an inch below the top of the vertical rail at the rear of the magazine. All modern magazines are so constructed, but there are some surplus mags which differ slightly. These magazines have the hole just a fraction of an inch too low, and will not lock properly into the firearm. This was done intentionally, by the military, so that the magazines could be fitted to particular runs of rifles, some of which might vary due to wartime production economies. The solution is simply to slightly raise, and enlarge the hole with a file. In many cases, you will find that this has already been done, either by the Army, a factory refurbishment, or a previous owner. If you look at the photo of my stick magazine, above, you will note that the hole for the catch is somewhat oval. Compare this to the photo at left, of an unmodified, WWII surplus, magazine, next to a modified magazine, and you will note that the hole for the catch is round. If you should purchase a surplus stick magazine, which was never issued, and still in the wrap, you may have to perform this little task yourself. The best tool for this is a plain old half round file, though a moto tool might also be used, if proper care is exercised. Using a file, you should check the fit of the magazine after every few strokes. It is very important not to take off too much metal, or the magazine will be ruined, at least for your particular gun. You can always take off a bit more metal, but you can not add it back on again, if you take off too much. I want to emphasize the fact that these magazines are not defective. Having to make this modification is normal, and the magazines were made this way intentionally, so that the magazines could be fitted to any run of Thompsons, made by any manufacturer. As a matter of fact, if you have an older Thompson, this modification will not be needed, and a modified magazine will not fit properly.
    During the clinton magazine ban, the stick magazines were in relatively good supply, and once the initial panic ebbed, they were available at reasonable prices. At the same time, drum magazines were nearly impossible to find, and once found, sold for nearly as much money as the, rather expensive, guns did themselves. The stick magazines are now easily available, very cheap, and are legal in most places. For about $100, I bought a set of seven, shown to the right along side the original stick that came with the gun. All needed modification in order to fit in my gun. This is cheaper than most pistol magazines, and is probably a reflection of the fact that there are millions of sticks out there, made for war time M1 Thompsons, but not too many civilian owned models these days. The drums, too, are more readily available, though in all honesty, the introduction of the 30 round stick, for war use, makes the weight, complication, and expense of the drum a bit silly, and hard to justify. Still, along with my sticks, I have several drums. This is, after all, a Thompson, but more about that in the next section.

Installing the Thompson Drum

    When you get right down to it, this is the hallmark of the Thompson. The later M1 version of the Thompson only took the stick magazines, but the drum is still forever associated with the Thompson. Millions of sticks were manufactured (tens of millions, more likely), as compared to perhaps tens of thousands of drums; but the reality of the Thompson is, for most people, a gun with a drum magazine.
    Loading, winding, and installing the drum in a Thompson, is actually a matter of some difficulty. This is very unlike the quick insertion of a stick magazine. Even more difficult is the removal of the Thompson drum. The drum may only be removed, and installed, with the bolt held back. This would seem easy enough, but the Thompson has no automatic hold open for it's bolt, and the spring powering it has considerable force. What is needed is a third hand to hold the bolt back, while one hand grasps the Thompson, and the other inserts the drum magazine. The "Third Hand" is what Thompson calls it's special tool for engaging the bolt hold back lever. With a little practice, installing a Thompson magazine can be reduced from a difficulty, to a mere annoyance. No wonder the Army determined that it was unsuitable to field use. Step by step instructions are below.

Installing a Thompson Drum Magazine.
Imagine doing all of this out on a battle field, while you are being shot at, and holding an empty Thompson.
Insert the "Third Hand" key up the keyway, while depressing the magazine release. The Third Hand will remain locked in place, once you let go of the magazine release. You can leave it in, the whole time the drum magazine remains in place

A photo of the Third Hand is directly below:

Pull the cocking lever all the way to the rear, and push up on the "Third Hand". This will lock the bolt back. The top of the Third Hand trips a lever which holds the bolt open. Once the bolt is held open, the Third Hand may be removed, though it is a better practice to leave it locked in place, to prevent loss.

With the bolt now held back, insert the drum from the left side only. Inserting it from the right could damage drum locking tabs, or your gun. You will need to insert the guide rails of the magazine into the cut outs on the frame. It may help to partially release the magazine catch.

Push it in until it snaps into place. You are now ready to play Elliot Ness.

To remove the drum, you must insert the "Third Hand" back up the keyway, if it is not already there, and lock the bolt back, as during the initial installation. This is potentially dangerous, if the drum is still loaded. Needless to say, the safety needs to be on. The Third Hand fits up the same keyway that acts as a guide for the stick magazine rail. Thus the Third hand can not remain in the gun, if a stick magazine is to be inserted, though it can remain in a gun with a drum installed, or with no magazine in place.

Release the magazine catch, and slide the drum out the left side of the receiver. Never push it to the right. This photo shows why. If you look towards the lower left hand side of the photo, you will see a pair of convex extensions stamped into the metal plate affixed to the drum. These form a catch for the magazine release. Note that they are on the left hand side of the drum. Should you attempt to insert the magazine from the right side of the receiver, you will find the receiver opening too narrow, and the catches, being stamped into a sheet metal cover, will probably become deformed, and ruin the magazine. This will also scratch up your gun.

Loading the Thompson Drum Magazine.
Remove the winding key, by puling up in it's central tab, and sliding it back. Then lift the top cover to expose the inside of the magazine.

Filling the outer ring first, load five cartridges into each partition.

FIll the other partitions, as shown.

Replace the cover, and reinstall winding key. Note that the winding key only fits when lined up with two small slots milled into the winding spindle, shown here.

Wind magazine, according to size, and instructions inscribed on magazine body.
 9 to 11 clicks for the 50 round magazine
 4 to 6 clicks for the 10 round magazine
 7 to 9 clicks for the 39 round magazine
 15 to 18 clicks for the 100 round magazine

The Thompson Drums
These all metal, key wound magazines are one of the earlier drum magazine designs. Unlike many modern drums, the Thompson drum has no feed column, and can not be used in a firearm with a magazine well. They are held together by their winding keys, and may be left loaded, but unwound until they are used, to reduce spring fatigue. The letter designations for these magazines (L,C,XL,X) are based on the Roman numerals of their capacities.
The 50 Round (The "L")
This is the most famous and popular of all of the Thompson drums. The legendary "L" drum, made famous by gangsters, and FBI men alike. For most people, this is THE Thompson magazine.
Weight                4.75 pounds (loaded)
Diameter            6.6 Inches
Clicks to wind    9 to 11

The 10 Round (The "X")
This is the dreaded, and awkward "X" style drum  magazine. This is the Auto Ordnance answer to the ridiculous magazine ban which afflicted gun owners for ten years. The "X" designation was appropriate, as the ban which spawned this magazine was obscene. You can see that the cartridge guide is very much shortened; otherwise it seems to be constructed the same as the L style magazine.
Weight                3 pounds (loaded)
Diameter            6.6 Inches
Clicks to wind    4 to 6

The 39 Round (The XL)
Photo taken from web
The 39 round magazine is a single track drum, designed to greatly simplify the original design. You might also notice that the arms of the "spider" are considerably thinner, and that the guide by the feed lips is much shorter. This allows the first and only row of cartridges to hold 39 rounds, rather than the 30 rounds held in the first row of the dual track "L" magazine.
Weight                4 pounds (loaded)
Diameter            6.6 Inches
Clicks to wind    7 to 9

The 100 Round (The C)
Photo taken from web
The rarest, largest, and most expensive of the Thompson drums. These had three layers of cartridges, rather than the usual two, and were increased in diameter, over the standard "L" 50 round drums. These huge magazines were not without problems, and they were reputed to have some feed troubles. They also weighed a colossal 15 pounds, when loaded. It is believed that as few as 2500 of these were made, all together. It is difficult to say how many might still remain. There are some more recently made reproductions of the old "C" magazine, which work fine in semiautomatic Thompsons, but are not recommended for the full auto versions.
Weight                9 pounds (loaded)
Diameter             8.6 Inches
Clicks to wind    15 to 18

An M1 Drum
Photo taken from web
After going on about how one of the cardinal differences between the M1 Thompson, and previous versions, was it's lack of compatibility with drum magazines, I have to admit that there was one rare exception. I have almost no knowledge about this magazine, and do not even know if it was the gun, the magazine, or perhaps both, which required modification. It is ironic that the Army, having decided to abandon the original drums, then decided to spend time and effort to reinvent them for the new weapons, designed to abandon their use.

Converting the 10 round "X" magazine to increased capacity (coming)
     It is possible, with only a small amount of skill, and simple tools, to convert the dreaded 10 round "X" style magazine to hold either 30 rounds, or the full fifty. Doing so, a year or so ago, during the ban, would have been a quick ticket to prison. It is now perfectly legal, unless you live in one of the backward states listed below.
     A thirty round conversion is simply a matter of removing the guide tracks from the top, and bottom of the magazine body, and fitting a specially made ring to the spider. A fifty round conversion is a bit more involved, requiring, besides the removal of the old tracks, their replacement with a new set.
     I will post photos, and descriptions of my experiences as I complete the project. Another method is show below.

It is also possible to convert the drum to 30 round capacity, by modifying the feed tracks.  The instructions to the left are circulating right now, and were drawn up by Auto Ordnance, in response to the large number of ten round drums in circulation. Now that the ban has ended, there is no reason for Americans to be saddled by the limitations of the ten round drum.
     Unfortuantly, several states have quietly succeded from the union, and are no longer under the Constitution. Along with their fellow socialists in canada, the rulers of these rogue states have forbidden their subjects to own magazines which hold over ten rounds.
     California,  Hawaii, New Jersey and New York all have bans against magazines holding over 10 rounds, and Massachusetts requires a special license. Maryland bans magazines which hold over 20 rounds.
     In addition to some state restrictions, some localities (like chicago), may have bans of their own. The prudent gun owner will want to check the law before undertalking such a project.

Disassembling the Thompson
Before doing anything else, remove any magazine which may be in the gun, point the muzzle in a safe direction, check to make certain that the chamber is empty, set the safety to Fire, and pull the trigger to release spring tension. The gun is now ready to disassemble. You should have a screwdriver handy before starting disassembly.

Turn the gun upside down, and depress the frame release button. located at the bottom rear of the frame. You may need to use a coin, or screwdriver. The release button is spring loaded, and is not captive, so that it may drop, or be launched from the bottom of the gun during disassembly.

The upper and lower portions of the frame will now slide apart, until the lower section goes about halfway back. It will then catch on the trigger group.

At the halfway point, use your screwdriver to slip under the upper receiver, and again depress the frame retaining button. This will permit the lower section to be drawn completely off the upper. Once again, be on guard against the release button dropping or being launched from the upper receiver.

The upper and lower sections are now separated, allowing access to the internal parts for cleaning, and lubrication. Actually, all of the manufacturer recommended lubrication points may be reached with no further disassembly.

The twin recoil springs will need to be removed first. They ride in the dual rails of the recoil spring guide. The springs, and guide, may be removed as a single unit, by pushing forward a bit, and pulling straight up. Be aware that the recoil spring guide will be under some pressure from the partially compressed recoil springs, and has the potential of launching itself across the room. The base of the recoil spring guide is notched to fit with the firing pin pilot. Once the guide is removed, the firing pin pilot, under tension from the firing pin spring, will extend from the rear of the upper receiver.

After removal of the recoil springs, and guide, slide the Firing pin pilot, and firing pin spring, out the back of the upper .receiver

Tipping the receiver up, will allow the hammer to fall free from the bolt, and out the back of the upper receiver, following the firing pin pilot. The hammer, oddly enough, is a simple cylinder of steel.

With the bolt all the way to the rear of the upper receiver it will be possible to remove the bolt handle by simply pulling it up and out of the bolt and upper receiver

With the bolt handle removed, the bolt may be easily removed from the bottom of the upper receiver.

Note the heavy, and rather large bolt. Also note that the bolt is drilled out for having a bolt handle at the top, or at the side, for use in either the M1928 model, or the M-1.

The upper receiver of the Thompson, stripped, and ready for cleaning and lubrication. The firing pin is located inside of the bolt, and is not designed to be removed for normal maintenance. Note that the current production Thompson uses a pure blowback action, with no locking of the bolt. Note also, that there is no Blish device in the current production models. The Blish device was an H shaped piece of brass or bronze which was a part of the original design. It's function was to reduce the cyclic rate of the gun. Such a device is hardly required in a semi auto firearm, and even it's relevance for the full auto version was a matter of debate.

Reassemble of the Thompson is similar to the disassembly process.

The bolt is inserted to the rear of the upper receiver, and it's opening for the bolt handle is matched up with the opening  on the top of the upper receiver. This will allow for installation of the bolt handle, which will lock the bolt in place. Once this is done, the bolt is pushed all the way forward. 

Once the bolt is replaced, by sitting it in the rear of the upper receiver, and then pushing it all the way forward, the hammer is pushed into the back of the bolt.

The firing pin spring, and pilot, are then pushed through the rear of the upper receiver, and into the bolt. This will fully seat the hammer.

The recoil springs are then inserted into their openings in the bolt, and the compressed slightly. Note, once again, the notch in the base of the recoil spring guide. This is designed to nest with a notch in the firing pin pilot.

Pushing forward on the firing pin pilot, while pressing down on the base of the recoil spring guide will mate the two parts, and seat them in the frame. At this point, the upper receiver is fully assembled, and ready to be reinstalled onto the frame. Note that you may need to depress the frame release button, before mating the  upper and lower portions of the gun, though this is not always required.

Modifying the New Style Thompson Magazine Catch.
     For reasons beyond comprehension, the magazine catch on the newer Thompson models has been changed. This imposes the  requirement that surplus military stick magazines be modified before they will fit the newer civilian guns. As an alternative, the magazine catch itself might be modified, though I do not recommend this approach. I am far more comfortable with taking a chance on hacking up a $20 magazine, then on grinding away at a $1000 firearm.
      Performing the modification will require, in addition to courage, a Dremel tool, or a file, and a dowel. The magazine catch must first be removed from the firearm. It is then reshaped, and reinstalled. There are two problems with attempting this modification, about which I feel obligated to warn the home gunsmith. The first is that taking off too much metal will ruin the magazine catch. The second is that the purchase of a new magazine catch is not a guaranteed fail safe. A new catch may need some hand fitting. Probably the best procedure to follow, is to remove the original catch, setting it aside, and purchase a new catch, then attempting the modifications on the new catch, thus retaining the original in case of mishap.
     In truth, it is not the catch, but the actual frame itself that has been changed. In order to make it more difficult for the intrepid home gunsmith to install full auto parts for a full auto conversion. The change in frame dimension means that the standard magazine catch is about 1/10 of an inch too high, for the standard stick magazine.
     I have included the instructions for the modification below; but will probably not attempt it myself. The instructions below are for reference purposes only, and I do not recommend that you perform this modification. If any one has attempted this procedure, either with success, or without, I would appreciate hearing about it.

The magazine catch must be modified by lowering the lip that engages the magazine .100" while maintaining the original contours and shape.
Make certain that the firearm is unloaded, place the safety in the fire position and squeeze the trigger.
Using a dowel or other object that will not mar the finish of the frame push up on the pivot plate finger that holds the safety lever, push the safety out.
After you have removed the safety, move the pivot plate so the ends of the pins are flush with the side of the trigger frame.
Pivot the magazine catch out far enough to clear the magazine engaging protrusion from the hole in the trigger guard.
Push on the pin part of the mag catch on the far side while pulling the catch out of the hole.
Once the magazine engaging protrusion has cleared the side of the trigger guard, carefully allow the catch to rotate and unwind the spring.
Remove the catch from the trigger housing . (Assemble in reverse.)
When re shaping the magazine catch, you must duplicate all the contours and angles when lowering the engaging surface.
Removing .100" will allow use of unmodified GI magazines.
Be careful not to remove too much metal.
You may have to re fit and test several times to achieve the optimal shape.

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