reconbob

I did quick check of a dozen stocks and I found one with this mark. This stock has the cross bolt, but no other markings. Bob

I have some M1928 stocks I will look closely and see if they have a similar mark. Bob

Yes, I saw that picture in a biography of Puller. I did not know the M1921 extractor was different than the M1928 extractor? Bob

I don’t think that is a stamped marking. M1928 stocks frequently have letters or numbers to match the parts for assembly stamped or marked with chalk on the stock under the buttplate, and on the inside of the buttplate and on the stock slide. But these marks are clearly impressions made by the stamps. On your stock the X is not an impression but the result of the surrounding wood being impressed and leaving a rough X as a result. Maybe this is an impression made by some tool or fixture to hold the the stock during manufacture? My $0.02 Bob

This is a clever fix, but I think could accurately be described as a blacksmith approach. If correct tools are not available I guess any port in a storm. I do not think it is a good idea to randomly heat a trigger frame red hot, because the line between heating and burning is a fine one. If the steel is over-heated or "burnt" it will become brittle. I have seen many frames like this that are so battered that I assumed it was not an attempt to remove the frame from the receiver, but an attempt to destroy or demilitarize the frame. A better safer fix is to clamp the trigger frame in a Bridgeport type mill as shown and use a standard 3/16" wide x 5/8" keyseat cutter. The T- slot in the trigger frame is 0.190" x 0.660" so frequently one pass thru the T-slot is all that is needed. Bob

Sears are as hard as files so any markings would have been done before heat treatment. Bob

This is a quality copy of U.S. Ordnance drawing "Thompson Submachine Gun, Cal. .45 M1928A1 Longitudinal Section". The original date of the drawing is December 31, 1941 with the latest update dated April 20, 1945. Full size 24" x 40". I found this in Doug's (Richardson) files. The drawing is of interest because there are no measurements or dimensions on the drawing. it is a cutaway view of a complete assembled M1928A1 Thompson, with every part indicated by an arrow with a leader going to the name and Ordnance drawing number of the part. Also of interest is that the M1928A1 Thompson depicted has a finned barrel, but an M1A1 rear sight with the triangular guards. The 28A1 Thompson was no longer in production in April of 1945 so who knows what they were thinking. This is a rare drawing because it has no drawing number and so does not show up in any searches of the archives. They moved most of the U.S. Ordnance technical archives to Picatinny Arsenal, and I know that not everything made it there. (For example - the drawing for the M1A1 Thompson bolt.) You can get drawings from the Data Release Officer under the Freedom of Information Act, but they search by drawing number, not name. My guess is back in the day Doug had his sources and was able to get this before it was lost during the move to Picatinny. I am selling fresh, new prints/copies of this drawing for $25. It gets shipped rolled up in a tube, not folded. Postage is $12.50. If you live in New Jersey it may be $1 less, if you live in California, it may be $1 more, but $12.50 for all. You can send check of money order made out to Robert Bower, and mail to: Phila Ordnance, 222 Roesch Ave, Oreland, PA 19075. Thanks Bob/Phila Ord

We have to remember that - except for a couple of oddball guns that had only a brief production life - the Thompson was the first submachine gun. And the gun designers were craftsmanship/commercial quality types who did not have simpler, later guns to copy or influence them. In those circumstances we get the one-piece, hardened steel grip mount. I also had never heard that the original pattern grip mount had a high breakage rate. Over all the many years I have been at this I have never seen a broken original pattern grip mount. But TD has put that idea to rest. Bob

The receiver in kit A is a Richardson receiver. He offered these with dummy/display buffer pilots and actuator knobs and you can see the Phillips head screw holding the actuator knob. These receivers were made many years ago and while they may have been OK with ATF back then, now the ATF does not allow the machining of the angle cuts for the bronze even if the rest of the receiver is solid. Bob

I need a late type, square front, 3 piece grip mount. Condition can be good or better, does not have to be pristine. If you have one for sale please email me at Philaord@aol.com. Thanks Bob

I do not have a Stevens trench gun. But I do have a M1903A3. Now, this is not an exhaustive study, but I took a look and the Thompson and M1903A3 stamped swivels are quite different. Once again, the M1903A3 is 0.030" longer, but I found one that was only 0.015" longer which did fit into the cutout for the Thompson. Thompson on the right. It has a little slot where the 03A3 is smooth. Also on the underside the 03A3has a wider slot. This is because the 03A3 is a "sandwich" made from two pieces whereas the Thompson is one piece - 03A3 on the left. There is so much to learn... Bob

Not everyone who frequents this board is an "expert", many are just looking for info. It's happened here again that a guy thinks that his M1903 Springfield swivel is a Thompson swivel and has modified the cutout in the stock (or forend) to be able to fit the swivel. The two swivels look exactly alike and the M1903 swivel is only .030" longer than the Thompson swivel, but that is enough where you can't jam it into the cutout. Once you know what to look for, the next time you are digging thru a box of parts at a gun show, you will be able to tell at a glance Thompson vs. M1903. Here are the swivels - M1903 Springfield on the right - Here is the side view - The Thompson is on the right. It is a little thicker but the thing to look for is the slight angle on the end of the M1903 vs, the square end on the Thompson OK, now YOU are an expert! Bob

If the gun fires one or two rounds when you let off the trigger, I’d say the bolt is not recoiling far enough back to be held by the sear. The bolt not back on last shot could also be short recoil or the trip/mag follower/disconnector malfunction. I consider S&B and IMI to be the hottest .45 ACP ammo. If the gun works with that ammo, the barrel is on its way to being shot out. One test you can do is fire one round with the gun on semi. Pull the trigger and hold it tight - the bolt should recoil and be held by the sear. The gun cleaner and air gun is a bad idea. There is no clearance for dirt/fouling to get blown out of the pocket in the trigger frame. The sear and sear lever are right up against the sides of the pocket, and the bottom rear of the pocket has no openings. The sear, sear lever, and trigger springs are in upside down blind holes that all the crud is going to get blown into, not out of. The disconnector spring is in a blind hole. Bob

Here is the big picture Bob

Just got this from a friend. Have not seen it before. I think the picture speaks for itself. If you zoom it, It looks like something is wrapped around the trigger frame? Also, judging by the bright spots in the magazine witness holes, it’s loaded. Bob

Thanks, I will take a look. Bob

I have had this magazine catch for years. It appears to be a magazine catch with no "bump" to engage the slot on a drum. It has the Savage S. This is the only one of these I have ever seen. Maybe it is pictured in one of the reference books? Bob

For the longest time I thought the quick way to identify a new manufacture fixed rear M1 sight was to look for the checkering or hatching around the rear sight hole to reduce glare. I saw a sight on GB that looked all original and correct - except no hatching - so I got it to examine. Now, the only source I know of for new manufacture/fake M1 sights are the ones they made to put in the "Russian" M1928A1 kits so they could sell the Lyman 55B sight as an "extra". The "Russian" fixed sight is easily recognized because the fake LYMAN stamp is the wrong size - maybe twice as big as original. The sight I just got is correct in every way, and i would say it is original, but there is no hatching around the sight hole. Here are 4 sights - On the left fake "Russian" sight, next original with no hatching, next original with hatching, and on the right older sight with the full LYMAN address. This sight has the hatching, but it is so faint that you can only see it viewed with a magnifying glass. Here are the apertures. On left, old sight with Middlefield address and barely visible hatching. On the right, original with no hatching On left original sight with hatching. On right "Russian" sight with no hatching. I would say that the presence or absence of the hatching is not the last word. It could have no hatching and be correct. The "giveaway" for the fake sight is the oversized LYMAN stamp. Bob

I have never had a problem with a Richardson receiver, but in my travels I have encountered this problem - usually with aftermarket barrels. The thing to do would be to put the barrel in a lathe and file the thread major with a flat file at low RPMs. This should enable the barrel to turn on a couple more turns. If you get the barrel to screw in 1/2 way I would use fine-to-medium valve grinding compound. Hold the barrel in a padded vise. Put a generous amount on the barrel threads and screw the receiver onto the barrel. When it won't turn any more use a cutoff broom handle or similar piece of wood that will not mar the receiver and use it as a handle to turn on/turn off, turn on/turn off the receiver onto the barrel. You will see that the barrel will turn on a little farther each time. If needed apply more compound to the threads. You should be able to get the barrel to turn all the way on in a few minutes. Once the barrel hits the shoulder of the receiver you're finished. Clean all the compound out of the receiver and off the barrel threads and you are all set. Only 0.001" can be enough extra material either on the barrel or the receiver to make a barrel too tight to screw on. While this may not seem like a precision approach, I have used it dozens of times over the years and it does no harm to the receiver or the barrel. The only "damage" is the bluing will be rubbed off the receiver and barrel threads, but when the barrel is fitted you can't see this and there is no danger of corrosion. Bob

The height of the receiver should be 1.430”. If there is a step and the barrel is the correct 1.00” diameter and the receiver is the correct 1.430” then the next thought is that the hole for the barrel is drilled a little too high. Bob

I never saw this, but if the barrel is original (Savage S or Steven’s square S) with the proof P at top dead center I would figure could be result of wartime production. Measured the diameter of the barrel. It should be 1 inch. Bob

Found in Doug's papers - This is a print of a Ordnance Department B&W photo (Negative #A-692) showing a M1921 barrel with small compensator and corresponding small diameter of barrel where the comp screws on. This is barrel "A" in the photo and is labelled a "standard" barrel. Barrel "B" is what we now know as a M1928 barrel and comp with the larger diameter and longer comp and the large diameter of the barrel where the comp screws on. This is the "proposed" barrel. It's too bad there is no date on this, but it is (I think) interesting. Bob

I had a guy in the shop today that had questions about recoil springs and how to know when it is time to replace them. For some reason he thought that coil springs never show wear. This is incorrect. Coil springs ALWAYS show wear, but with a Thompson recoil spring it is a more subtle thing to recognize. Here is the recoil spring from a Browning Automatic Rifle showing obvious wear by the flattening of the coils of the spring. It's not a great photo but in the middle of the picture you can see the coils are noticeably flattened. Here is a Garand recoil spring - same situation - the flattened coils are obvious - Not so easy with a Thompson but it still happens. Here is a new recoil spring - And here is one with the flattening of the coils, but not as obvious as BAR/Garand because on the Thompson the diameter of the wire is a little smaller. But it's there - the easy way to recognize it is to compare the flat coils in the middle to the round coils in the corners of the photo. So yes, coil springs always show wear and eventually wear out. The best/easiest way to check a Thompson recoil spring is to measure it. It should be 11 5/16" +/- 5/16" long. Bob

If the frame was spray painted that would fill up the pits and smooth it out and sandblasting would blow off the paint and expose the pitting instantly. Bob

If you sloowly pull the trigger when the sear finally trips it drags on the bottom of the bolt slowing it down and causing the jams. Your description of being able to fire long bursts but have the gun jam when you slowly pull the trigger is the exact example of this. I have had this conversation dozens of times over the years, mostly with guys that have rental ranges. Rookies come in and pull the trigger very slowly as if the Thompson is a target rifle….and the gun jams. The way to shoot a Thompson is to fully and decisively pull the trigger then let it go. If you want to fire single shots use the selector. If you found a bolt that works even with the “target” trigger pull I would figure the bolt is worn in some way. My $0.02 Bob