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Black Dog Thompson conversion kit rimfire buzz gun fun: has that Thompson been sitting in the safe because ammo prices are just too brutal? Adapt it to fire inexpensive rimfire ammo.

Back in the day, Thompson owners were happy to let a friend put a magazine or two through their Tommy Guns. Now, high ammunition prices mean few can afford to be so generous, or even shoot personally as much as they would like.


Fortunately, two reliable .22 Long Rifle conversion kits are available for them. The older .22 Long Rifle conversion kit is manufactured by Jonathan Arthur Ciener. The Ciener .22 Long Rifle conversion runs well, but at an unrealistically fast rate of 1100 rounds per minute.

That rate does not duplicate the sound of a Thompson Submachine Gun. For comparison, I recently tested a Model 1921 Thompson that cycled at 925 rpm. A Model 1928 Thompson is slower at about 825 rpm. The World War II Models M1 and M1A are the slowest, at about 775 rpm.

A second .22 Long Rifle conversion kit is now in production at Black Dog Machine, LLC. It comes with two operating springs, a hard one that ran 816 rpm in a World War II M1 Thompson and a softer spring that yielded 761 rpm in the same gun.

You can slow it down to an easy-on-the-wallet 650 rpm by installing a .035"-.375"-5.5 CPI x 12.0-inch spring, which you can get from the Wildwood Test Facility if you can't find one locally.

The Black Dog Thompson kit, with one exception, contains every part needed to convert any Thompson to .22 Long Rifle. Owners of Model 1921 Thompsons will need one more part, the operating spring guide rod of a Model 1928 Thompson.

The guide rod is not a complex part. If an original 1928 guide rod is not available, it would not be difficult to make a substitute from round bar stock. Though not tested, a short piece of 3/8" threaded rod and a couple of nuts would likely make a suitable, but not pretty, substitute as well.

Though Black Dog Machine, LLC is new to the business of making .22 Long Rifle conversions for Thompson submachine guns, Black Dog is an established manufacturer of reliable high capacity .22 Long Rifle magazines. Currently, Black Dog produces high capacity magazines for Ruger 10-22s and .22 Long Rifle converted Ruger Mini-14s and AC556s. Black Dog also makes high capacity magazines for .22 Long Rifle converted Thompsons, Uzis and M16s.


.22 Long Rifle Slow Fire Thompson Conversion

Jonathan Arthur Ciener made and sold the first reliable .22 Long Rifle conversion kit that was made for a Thompson Submachine Gun. In order to achieve more realistic practice with a .22 Long Rifle Thompson, Dr. Ed Shaughnessy, a firearms designer who also teaches advanced engineering courses at Duke University, Merle Bitikofer and the author collaborated to reduce the .22 Long Rifle Ciener/Thompson's cyclic rate.


Eighteen months were required, and 21,500 rounds of ammunition were expended before solving all of the problems. Though many problems were encountered, most were solved by significantly reducing the drag on the bolt while adding a bit of weight to it and increasing the firing pin's striking force.

After these modifications, springs of varying tensions were used to match the cyclic rate of any model of the .45 ACP Thompson. Moreover, a super slow rate of 650 rpm was achieved as well.

There was an unexpected downside to the cyclic rate reduction however. The weights that were added to the Ciener .22 Long Rifle Thompson bolt accelerated the wear to the bolt's aluminum sear face. When the trigger was pulled, the experimental Slow Fire .22 Long Rifle Thompson prototype would not cease firing until the magazine was emptied. Due to the low recoil of the .22 Long Rifle cartridge and the Thompson's 10-pound weight, it was easy enough to keep the runaway Thompson on target until the magazine had been exhausted, but that's no way to have an SMG work.

Merle Bitikofer repaired the worn aluminum sear face in short order. He machined away the worn aluminum sear face and replaced it with one made of steel.

Bitikofer made a prototype slow fire bolt for himself. His bolt was a bit more advanced than the author's. Bitikofer removed the bolt carrier's aluminum sear-face by machining away about .25" from the entire bottom of the aluminum bolt. He then replaced the missing aluminum with a bolt-fitting piece of steel. The new steel piece incorporated a sear face. The added weight of the new steel piece replaced the weights that were formerly necessary. Bitikofer's solution is truly elegant!

Merle Bitikofer shared the design of the Thompson Slow Fire .22 Long Rifle prototype with Black Dog Machine LLC. Black Dog made one hundred .22 Long Rifle Thompson conversion kits to test the market. Priced at $525, the original Black Dog Slow Fire Thompson kits were quickly sold. A second run of Black Dog kits is being produced at this moment.

Black Dog Slow Fire Conversion Installation

Two 30-round magazines are supplied with each Black Dog .22 Long Rifle Thompson Slow Fire conversion kit. Each kit includes everything that is needed to convert either a Model 1928 or an M1 Thompson to .22 Long Rifle.

First-time installation of the Black Dog conversion kit will probably require about 30 minutes. After becoming familiar with the technique though, subsequent installations should not require more than 10 minutes. Converting from .22 Long Rifle back to .45 ACP requires less time.

Begin the installation by assuring that the Thompson is unloaded and that the bolt is forward (at rest). Set the safety lever to the fire position and set the fire control selector to full auto. Place the Thompson upside down on a workbench. While pressing the trigger frame release button downward, simultaneously pull the trigger and slide the trigger frame and stock rearward until they are separated from the receiver.

Remove the operating spring and the .45 ACP bolt and set them aside. The .45 ACP ejector must be removed before installing the .22 Long Rifle barrel. If care is not taken, the Thompson's receiver can be scratched while accomplishing this.


Fortunately, a simple precaution will prevent harm. Locate a thin plastic card and a screwdriver that has a very thin, sharp-edged blade. Slip the sharp-edged screwdriver blade under the ejector. Lift the ejector and carefully slip the plastic card under the ejector's sharp point. Hold the card under the sharp point as the ejector is unscrewed from the receiver.

Lay aside the ejector. If a spare ejector is available, the sharp end can be removed and then the pointless ejector can be installed. This is for cosmetic reasons only. The Black Dog barrel has an integral ejector so the original .45 ACP ejector is unneeded.

This is a good time to thoroughly clean and heavily lubricate the bore of the .45 ACP barrel. Heavy lubrication is unnecessary for functioning, but it will help to protect the .45 ACP barrel from rust if the hot .22 Long Rifle barrel causes it to "sweat."

With the receiver still inverted, slide the Black Dog .22 Long Rifle barrel partially into the breech end of the .45 ACP barrel. Make certain that the .22 Long Rifle feed ramp is centered and then push the .22 Long Rifle barrel all the way into the .45 ACP barrel. Secure the barrel at the muzzle with the Black Dog barrel nut. Don't use any tools. Tighten the barrel nut finger-tight only.

The Black Dog conversion kit is supplied with one bolt but two cocking knobs. One cocking knob slips into the top of the Black Dog bolt. In this configuration, it is used with either a Model 1921 or a Model 1928 Thompson. The second knob is for use with an M1 or an M1A Thompson. It fits the hole in the right the side of the Black Dog bolt. Install the cocking knob after placing the bolt into the receiver but before installing the operating spring.

After placing the .22 Long Rifle bolt into the Thompson's receiver and installing the cocking knob, select an operating spring and insert one end into the bolt. Insert the operating spring guide rod into the opposite end of the spring.

A simple technique can be employed when compressing an M1 Thompson's operating spring that will avoid kinking it. Before compressing the spring, pull the bolt rearward and leave a gap of about 1.25 inches between the bolt and the rear inner face of the receiver.



Hold the bolt firmly and compress the spring with the guide rod. Push the guide rod until its end is flush with the end of the receiver. Hold the guide rod and allow the bolt to move forward until it stops. Slip the guide rod retainer/buffer over the guide rod.

Slide the trigger frame and stock back onto the receiver. Done!

.22 Long Rifle Ammunition Precautions

We tried a variety of commonly available .22 Long Rifle high velocity ammunition types with the Black Dog .22 Long Rifle Thompson conversion kit. Many brands produced good results. An exception was Remington "Gold" .22 Long Rifle ammunition. Many cases ruptured while testing it, a result we had also had with a .22 Long Rifle converted Uzi submachine gun. Ruptured cases can damage the gun and injure the shooter.



This is not to imply that Remington "Gold" .22 Long Rifle ammunition is substandard. In other tests, it has produced very good results. Remington "Gold" was the ammo of choice for an M16/.22 Long Rifle conversion, a Ruger AC556/.22 Long Rifle conversion and an HK33/.22 Long Rifle conversion. Remington "Gold" also performs very well in John Norrell's Ruger 10/22 full auto conversions.

So, "What is the problem with Remington 'Gold'?" Short answer, "There is no problem." Remington "Gold" is excellent ammunition, but it is made to a different specification. Both the Thompson and the Uzi fire from an open bolt and neither runs well with Remington "Gold." On the other hand, the M16/.22 Long Rifle, the Ruger AC556/.22 Long Rifle, the HK33/.22 Long Rifle and John Norrell's Ruger full auto 10/22 all fire from a closed bolt. Each of these guns run very well with Remington "Gold." As with many guns, these submachine guns have an ammo preference. For best performance, determine the type of ammo that your gun prefers and stick with it.

Shooting the Black Dog Thompson

With that exception, the Black Dog .22 Long Rifle Thompson shot most brands of high velocity ammunition with near 100% reliability. Federal 550 .22 Long Rifle bulk ammo was chosen for the lengthy performance tests due to its reliability, availability and relatively low cost.

The first 25 rounds are easy to load into the Black Dog .22 Long Rifle 30-round magazine and the final five are only slightly more difficult. The magazine spring is well matched to the relatively slow cyclic rate of the .22 Long Rifle Thompson. In spite of the relatively weak magazine spring, the Black Dog magazine has no difficulty in elevating a fresh round in time to meet the returning bolt as the Thompson fires.

One simple precaution should be observed when inserting a magazine into the .22 Long Rifle Thompson's magazine well. If the magazine is slammed forcefully into the magazine well while the Thompson's bolt is retracted (cocked), the magazine can be driven too far into the well.

If that should occur, the ejector can be bent upward into the path of the bolt. Damage of this sort is easily repairable but it can be avoided in one of two ways. First, when placing the magazine into the magazine well, be gentle. Don't slam it home. Alternately, leave the bolt closed (forward) when placing the magazine into the well. In this condition, the ejector rests against the bolt. If the magazine is pushed forcefully into place, the bolt will prevent the ejector from being bent.

At the slower Black Dog cyclic rates, the Thompson's trigger can be manipulated quickly to fire a single round at will. Though firing a single round is often the best course of action, the Black Dog Thompson is very controllable. It begs to engage multiple targets with a long burst.

A good technique is to aim at the first target in an array and move the gun horizontally in a smooth sweeping motion. Ideally, the muzzle should traverse the target array at a rate of about 10 to 24 inches per second. Mentally counting, "One thousand and one, one thousand and two" while firing helps to set the pace. Depending on the operating spring that is chosen, a bullet will strike every 1.5 to 2.5 inches. This cadence-will mow down a line of small targets.

After the last round in the magazine has been fired, the Black Dog magazine follower rises into the path of the bolt. This action stops the bolt before the firing pin strikes the face of the barrel--thus preventing damage to either the firing pin or to the barrel's face.


Due to the quality of its materials and workmanship, a Black Dog .22 Long Rifle Thompson conversion should provide years of faithful service. That does not mean that it, or any reliable .22 Long Rifle conversion, will be totally trouble-free.

Every .22 Long Rifle machine gun that has been tested at the Wildwood Test Facility has functioned better in hot weather than in cold. In hot weather, the ammunition seems to perform better and the fouling that accumulates inside of the receiver does not become hard and unyielding as it does in cold weather.


Below is a list of things to check in the event of malfunctions. These tips apply to all .22 Long Rifle submachine guns, not just to Black Dog conversions.

1. Thoroughly clean the gun, paying particular attention to the bolt, the bolt's travel path and the chamber.

2. A. 22 Long Rifle cartridge has very little extra power available to overcome frictional drag on the bolt. Look for any friction points that may be slowing the bolt. If you find any, carefully polish them. Keep the bolt travel path dry or lubricate it lightly. Some prefer dry graphite lubrication (E&L Dry Gun Lube is a common choice).

3. Particularly in cold weather, try every type of ammo that you can find. You may find one type that functions very well. CCI Mini-Mags and Winchester Super X ammunition have often proved to run well in cold weather.

4. Test every type magazine that you can find that fits the gun. If possible, test several magazines of each type. You may find one magazine that looks just like the rest but it functions well while the others don't. If such is the case, try to discover why one magazine works and the other does not. It is possible that the failing magazine can be repaired.

5. If the gun feeds well but it fails to eject the cartridge properly, examine the ejector to see if it is loose, bent or worn.

6. The extractor can effect both extraction and feeding. Remove the bolt and examine it closely. Has the extractor-spring been damaged? Is there dirt under the extractor? Dirt can prevent the extractor from properly guiding the fired round out of the ejection port. Is the inner face of the extractor smooth and parallel to the bolt face? Reinstall the bolt and watch the bolt as it chambers a dummy round. Does the extractor slip easily over the cartridge's rim? If it does not, that robs energy from the bolt. You may be able to polish the forward the face of the extractor to reduce friction as it snaps over the cartridge rim.

Following these steps will solve most of the problems that occur with any .22 Long Rifle submachine gun that was once reliable but is now failing. Due to its quality and to the simplicity of its operation though, with occasional cleaning the Black Dog Thompson .22 Long Rifle conversion will likely remain trouble fret for years of frequent shooting.


Due to the risk of marring the receiver, some Thompson owners may be reluctant to remove the ejector from their Thompson. This removal is required before a Black Dog Thompson .22 kit can be installed. For these owners, there is a simple solution, Merle Bitikofer can modify the Black Dog kit's bolt and barrel in a manner that will allow these parts to be installed without first removing the Thompson's ejector. He charges $75 for this service.

If the cocking knob on a Model 1921 or Model 1928 Thompson is a bit loose, it will function just fine, if the knob rubs the outside of the receiver though, it will leave marks on the receiver's finish. This is a common problem. Many Thompsons will exhibit wear of this sort before the Black Dog .22 conversion kit has been installed. If the Thompson of the Black Dog kit's owner is unmarked by the original cocking knob, Merle Bitikofer can supply a modified cocking knob that will avoid creating this minor blemish.

Bitikofer also makes a useful accessory for the Black Dog .22 Thompson kit. It is a new barrel nut that incorporates a suppressor mount ($.40). The mount's threads are .5X28. This is a common thread pattern. Many suppressors incorporate it.


A special .22 cal suppressor is not required for the .22 Thompson. If a 9mm or a 45 ACP suppressor is available, either will quiet a .22 converted Thompson quite well. The larger internal volume of a 9mm or .45 ACP suppressor seems to compensate for the oversize notes in their baffles.

In one respect, either a 9mm suppressor or a .45 ACP suppressor is more desirable for a suppressed .22 Thompson than a .22 caliber suppressor. The oversize baffle holes of the 9mm and .45 ACP suppressors mean if there is a minor misalignment between the barrel's bore and the suppressor, a baffle strike is less likely. Whether using a.22 suppressor, a 9mm suppressor or a .45 ACP suppressor, before firing always use a straight, bore-fitting, drill rod: to check the suppressor's alignment with the bore.

Be certain to use standard velocity (subsonic) .22 ammunition with the suppressor. If you do not, the benefit of the suppressor will be negligible. High velocity .22 ammunition will cause a supersonic shock wave to form. In turn, the shock wave causes a loud "crack." This "crack" is louder than the noise that is caused by the combustion of the powder within the cartridge.


.22 Long Rifle Thompson Conversion Kit

Black Dog Machine, LLC

9986 Cherry Lane, Dept SGN, Nampa, ID 83687

Phone:(208) 465-1940 | Fax: (208) 466-9479

Dry Graphite Spray-on Lubrication

E&L Manufacturing

4177 Riddle By-Pass Road, Dept. SGN, Riddle, OR 97469

Phone: (541) 874-2137 | Fax: (541) 874-3107

Super Slow 650 RPM Operating Spring

($10 includes shipping)

Wildwood Test Facility, Box 404, Dept. SGN, Trinity, NC 27370

Authentic-looking .22 Magazine

Jonathan Arthur Ciener

8700 Commerce Street, Cape Canaveral, FL 32920

By Captain Monty Mendenhall
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Author:Mendenhall, Monty
Publication:Shotgun News
Date:Nov 20, 2010
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