Some years ago, I became interested in the Auto-Ordnance Thompson semi-automatic carbine. After all, the world would be dull without the story of men and machine guns, and the Thompson is among the most interesting. While most of us will never own a true Thompson SMG, there are alternatives, and these alternatives are fascinating to fire and work with.
In some cases, the pride of ownership alone is worthwhile. For the rest, the Auto-Ordnance carbines are great for recreational shooting. I suppose it is safe to say that nothing puts as big a smile on your face as when you are handling a Thompson.
The Auto-Ordnance Thompson is a faithful reproduction of the original. The modern Thompson is in between the superior fit and finish of the Colt 1921 version and the later M1A1. The cooling fins and vertical foregrip are intact. Overall, the Thompson gives the impression of a firearm that is carefully made. Don’t ask where the Thompson carbine fits in the scheme of things. I cannot imagine a role in which another firearm wouldn’t serve better.
The longer barrel (16 inches versus the original’s 10 inches) dictated by Federal law means the new Thompson handles differently than the original. With a lack of a full-auto option, any number of modern self-loading rifles would best the Thompson as a personal defense firearm.
Trigger reset was slow and limited rapid fire and accuracy. However, nothing comes close for a pure fun factor. Owning the Thompson is an act of brashness all its own accord. We should all own as many things as possible — that have no clearly-defined purpose!
The Thompson may be addictive, but there is a problem. It is expensive to fire any factory centerfire round but firing a drum of 100 rounds of .45 ACP makes a dent in the wallet, quickly. Handloading is the only way to mitigate some of this cost.
Loading for the .45 Carbine
In my long loading life, I have loaded more .45 ACP cartridges than all the rest combined. Just the same, I approached the Thompson with a fresh start and a new eye. I wasn’t in the game to increase power — all that mattered was that the piece functioned.
When dealing with a blowback design, you increase power at your own risk. Battering is the result of a heavy hand with the powder measure.
Accuracy was problematic for the type of shooting I intended. However, I wished to obtain as much accuracy as possible. Sight regulation at 50 yards was important. While 100-yard shooting was interesting, 50 yards was more reasonable.
I like a challenge — sometimes — and hits were much easier to come by at 50 yards! I knew that it was best to begin with a standard 230-grains, 850 fps (pistol velocity) ‘hardball’ loading. I intended to substitute an affordable, hard cast, round nose, lead bullet for the military jacketed bullet. I had no idea as to feed reliability with SWC or JHP bullets, and they were not needed in this carbine.
Burn Rate: Fast or Slow
I learned some things about loading for a .45 ACP carbine. I believe that most of the velocity is built up in the first eight inches of barrel. Trying different loads, I noted that velocity did not notably increase as it does in a long barrel with the .357 Magnum and slow burning powder. That fact brought up the question of whether using a fast-burning powder wasted the advantage of rest of the barrel. It was tempting to experiment with slower-burning powder such as Accurate #7.
If you use a slower-burning powder, the end result was a heavy muzzle flash or even ejection port flash. Ejection port flash means the blowback action was unlocking too soon. In other words, the Thompson was unlocking before the powder was burned. This could not be a good thing, and the results were erratic as far as velocity and accuracy.
I learned quickly. The fast-burning powders were the best bet, as the Thompson was designed for military ball that used Bullseye powder. Sure, this wasn’t an original, but it was pretty close to the original Thompson without the Blish lock.
Loading for the locked-breech 1911 is far different. You may use a medium-burning powder in the locked breech Colt and produce longer lock time and greater accuracy — at least that is the theory.
With the carbine, faster burning loads are definitely the superior. Even with Titegroup powder — one of the cleanest burning propellants ever — there was some blowback of unburned powder. My hero for this work turned out to be Winchester 231 powder.
After some experimentation with 230-grain ball loads, I began cautiously working up loads with 230-grain Oregon Trail Laser Cast bullets. The 230-grain hardball equates to a 920-fps load in the 16-inch barreled Thompson. It seemed that a load of at least 870 fps (carbine, not pistol velocity) was required for reliable function.
There were no special considerations with crimp or powder selection, and the Thompson functioned fine with minimal barrel leading. As it turned out, the traditional loads from the various manuals that were listed near the maximum gave very good velocity and accuracy, with velocity in some cases nearing 1,100 fps.
This puts the .45 ACP in a different power category — like a .460 Rowland but with little recoil. Of course, you are paying quite a weight penalty using the carbine. With comparable powder charges, lead bullets gave a velocity advantage over the jacketed bullets, which was not surprising. However, the difference was more striking than was the case in a five-inch pistol.
For accuracy, the Thompson preferred jacketed bullets. I used the Hornady 230-grain FMJ and 230-grain FP. Feed and function were good. The 230-grain FP was the single most-accurate bullet used.
I was surprised to find that the Thompson fed most JHP bullet styles. I tested several of the factory loads I had on hand, including the Hornady 230-grain XTP. Velocity increase was more significant with this high velocity number.
Firing a few factory rounds, to confirm feed reliability with JHP bullets, led to experimentation with the Hornady XTP in 185-, 200-, and 230-grain weights. You easily perceive the difference in trajectory with these at 50–100 yards with the lighter bullets. The faster loads were not flat shooting, but they did not drop like the 230-grain loads either.
The 200-grain XTP proved to be the most accurate when addressing steel plates at the 100-yard range. I was also able to work up an acceptable loading using the Rainier 185-grain bullet. This affordable, plated bullet gave good results.
1921 Range Testing of the Thompson
In researching the Thompson carbine, I was intrigued by period literature outlining accuracy testing with the Thompson from a Mann rest. The Mann rest was a fixture often used to test intrinsic or absolute accuracy in firearms. The Thompson was fired in the semi-automatic mode for this test. According to a firing test undertaken with a Colt-produced Thompson on May 2, 1921, the Thompson was quite accurate.
Using Remington ammunition, the mean radius at 100 yards was 1.89 inches, 4.92 inches at 200 yards and 7.63 inches at 300 yards. At 500 yards, the radius greatly expanded to some 20.45 inches. There were poor results in another test. The shooter credited a bad lot of ammunition. A year later, another test showed less impressive results including a 200-yard group that showed an average mean radius of 5.8 inches at 200 yards.
In a test of the shooter and the machine, well-known writer Phillip Sharpe assumed the prone firing position and carefully placed five shots into 2.5 inches at 100 yards with a commercial Thompson. Sharpe reported a 1.5-inch 50-yard group as well. Could I equal Sharpe’s 1933 results with my new Auto-Ordnance carbine?
I had the advantage of a longer barrel and a modern CNC-produced carbine. Perhaps, my biggest advantage was well-developed handloads. However, the quality of the original Colt SMG was the wild card. I wondered, “Just how good was the Auto-Ordnance”
Old Versus New
A limiting factor was the trigger action. While there was plenty of leverage because the Thompson was so heavy — I could not whip the gun around with trigger pressure. Trigger compression was heavy at eight pounds.
I engaged in dry fire practice for over an hour — split into 15-minute increments — to gain an advantage on the range. The occasional brilliant group followed by a flyer were simultaneously encouraging and challenging.
In the end, firing from a solid braced position, I was able to secure several three-inch 100-yard groups with complete concentration and the proper trigger technique. However, this wasn’t the norm. The Thompson was more-or-less as accurate as the average unmodified .30 carbine or AK-47 rifle.
The shooting was most interesting. I emerged from the experiment with a new respect for the Thompson. The piece was more accurate than my first impression, and the Auto-Ordnance carbine proved very reliable. The Thompson remains among the finest recreational firearms I have ever handled and an interesting piece of history.
Heckler and Koch USC Carbine
After some time, when I was too busy to handload, I came back to the .45 ACP carbine in a big way. The Heckler and Koch USC carbine is among the most overlooked and underappreciated .45 ACP firearms ever manufactured. This is a dirt tough, modern, and reliable firearm.
As far as swinging on a fast-moving target, ergonomics, and combat ability, this semi-auto carbine considerably improved the Thompson’s performance. It isn’t any less expensive, but it is a reliable and useful personal defense firearm. I rate it at the top of the class in .45 ACP carbines.
Fortunately, when I obtained the HK, I had an ammo can of handloads marked THOMPSON. Would the HK perform as well with these loads? You bet! I have included results for both carbines.
Load Tables — Loading Results
All groups are measured in inches and all groups were fired at 50 yards.*Groups fired in Thompson carbine unless noted
|Bullet||Powder||Velocity (FPS)||Group (inches)|
|Ranier 185-grain JHP||7.5 Unique||1,260||3.6|
|Hornady 200-grain XTP||8.5 AA#5||1,110||3.0|
|Hornady 200-grain XTO||7.2 Unique||1,213||3.65|
|Hornady 230-grain FMJ||6.8 Unique||880||4.0|
|Hornady 230-grain XTP||7.0 Unique||966||3.25|
|Sierra 240-grain JHP||6.8 Unique||905||3.9|
|Oregon Trail Laser Cast bullets 200-grain SWC||7.2 Unique||1,222||4.0|
|230-grain RNL||8.0 AA#5||1,120||3.5|
|5.8 WW 231||1,090||3.15|
|5.2 WW 231||930||3.5|
Factory Ammunition Testing
|Bullet||Velocity (FPS)||Group (inches)|
|Winchester 230-grain FMJ||960||4.0|
|Black Hills 230-grain JHP||1,015||3.15|
|Heckler and Koch|
|Winchester 230-grain White Box JHP||1,001||2.5|
|Browning 230-grain X Bullet||1,020||2.8|
Remember to take your time, begin with the starting load, and be certain that you address the crimp properly. Loading for the .45 ACP carbine isn’t difficult, it simply requires attention to detail.