Ammunition

.45 ACP Handloading — Thompson SMG, HK Carbine

multiple types of .45 ACP bullets

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.

Auto Ordnance Thompson .45 ACP Carbine right profile with stick magazine
The Auto-Ordnance Thompson is a well-made and interesting piece of equipment.

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 Thompson

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.

Jacketed Hollow point bullet left, SWC bullet right
It wasn’t part of the original plan but as it turned out, both carbines feed both JHP- and SWC-type bullets just fine.

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.

Scottwerx Ruger .22 conversion, top, .45 ACP Thompson, bottom
At one time, the author has the Thompson bug so bad he owned a Scottwerx Ruger .22 conversion, top, and the .45 ACP Thompson.

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.

Bullet Selection

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.

Cartridge with unfired primer, left, and overpressure fired primer, right
That is an unfired primer, left. The primer on the right has been fired. This is a sign of excess pressure. When you reach this point, you are already in trouble.

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.

Two damaged cartridge casings
Loading can be dangerous! The bulged .45 ACP case on the left was fired in a Kimber Custom II. The pistol was not harmed by this dangerous overcharge — caused by seating the bullet too deeply. The .45 GAP, right, blew with a standard load during early development.

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.

Damaged hollow point with the bullet shoved deep into the case
A modern carbine that takes Glock magazines choked on the author’s handloads, and sometimes factory ball ammunition.

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.

close up of the hollow point of the Barnes X bullet
If the author was to hunt with the carbine — 50-yard deer or boar would not be out of the question. The Barnes X bullet would be ideal.

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.

Heckler and Koch USC carbine, left, profile
The bling appeal of the Thompson is one thing, and if that is your goal, go for it. However, if you need something to fight with, the HK USC is over-the-top effective!

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

BulletPowderVelocity (FPS)Group (inches)
Thompson SMG
Ranier 185-grain JHP
7.5 Unique 1,2603.6
HK Carbine3.0
Hornady 200-grain XTP8.5 AA#51,1103.0
HK Carbine2.8
Hornady 200-grain XTO7.2 Unique1,2133.65
HK Carbine2.5
Hornady 230-grain FMJ6.8 Unique8804.0
HK Carbine3.0
Hornady 230-grain XTP7.0 Unique9663.25
Sierra 240-grain JHP6.8 Unique9053.9
Oregon Trail Laser Cast bullets 200-grain SWC7.2 Unique1,2224.0
230-grain RNL8.0 AA#51,1203.5
5.8 WW 2311,0903.15
5.2 WW 2319303.5

                                                                           

Factory Ammunition Testing

BulletVelocity (FPS)Group (inches)
Thompson SMG
Winchester 230-grain FMJ9604.0
Black Hills 230-grain JHP1,0153.15
Heckler and Koch
Winchester 230-grain White Box JHP1,0012.5
Browning 230-grain X Bullet1,0202.8

                                                                                                                              

Conclusion

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.

Have you ever loaded for the .45 ACP carbine? What are your thoughts on the Auto-Ordnance Thompson or Heckler and Koch USC carbine? Share your answers in the comment section.

  • flip up sights on the HK USC .45 ACP carbine
  • Auto Ordnance Thompson .45 ACP Carbine right profile with stick magazine
  • Close up of the Auto Ordnance Thompson .45 ACP manufacture stamp
  • Heckler and Koch USC carbine, left, profile
  • Two damaged cartridge casings
  • multiple types of .45 ACP bullets
  • Cartridge with unfired primer, left, and overpressure fired primer, right
  • Heckler and Koch USC carbine, left, profile
  • Damaged hollow point with the bullet shoved deep into the case
  • Jacketed Hollow point bullet left, SWC bullet right
  • close up of the hollow point of the Barnes X bullet
  • Scottwerx Ruger .22 conversion, top, .45 ACP Thompson, bottom

About the Author:

Bob Campbell

Bob Campbell’s primary qualification is a lifelong love of firearms, writing, and scholarship. He holds a degree in Criminal Justice but is an autodidact in matters important to his readers. Campbell considers unarmed skills the first line of defense and the handgun the last resort. (He gets it honest- his uncle Jerry Campbell is in the Boxer’s Hall of Fame.)

Campbell has authored well over 6,000 articles columns and reviews and fourteen books for major publishers including Gun Digest, Skyhorse and Paladin Press. Campbell served as a peace officer and security professional and has made hundreds of arrests and been injured on the job more than once.

He has written curriculum on the university level, served as a lead missionary, and is desperately in love with Joyce. He is training his grandchildren not to be snowflakes. At an age when many are thinking of retirement, Bob is working a 60-hour week and awaits being taken up in a whirlwind many years in the future.


Published in
Black Belt Magazine
Combat Handguns
Handloader
Rifle Magazine
Handguns
Gun Digest
Gun World
Tactical World
SWAT Magazine
American Gunsmith
Gun Tests Magazine
Women and Guns
The Journal Voice of American Law Enforcement
Police Magazine
Law Enforcement Technology
The Firearms Instructor
Tactical World
Concealed Carry Magazine
Concealed Carry Handguns



Books published

Holsters for Combat and Concealed Carry
The 1911 Automatic Pistol
The Handgun in Personal Defense
The Illustrated Guide to Handgun Skills
The Hunter and the Hunted
The Gun Digest Book of Personal Defense
The Gun Digest Book of the 1911
The Gun Digest Book of the 1911 second edition
Dealing with the Great Ammunition Shortage
Commando Gunsmithing
The Ultimate Book of Gunfighting
Preppers Guide to Rifles
Preppers Guide to Shotguns
The Accurate Handgun
The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (7)

  1. Mr. Johnson

    I have used reloads in both the Thompson and the 1911 with gun results. Did not use difference load practice with 1911, Thompson or HK firearms.

    All are full length resized and loaded with a roll crimp. I cannot imagine a reason they would not work in either firearm.

  2. My Thompson has an aftermarket barrel, 16″ with Cutts Comp threaded back over it, which makes the barrel appear shorter by the length of the compensator. It has the military chamber, which is conical. Reloads from the Thompson will not function in a 1911 auto pistol. I have used lead 230 RN bullets with Unique forever. Incidentally, full autos fire from an open bolt which would drastically affect aiming in semi.

  3. My son bought a Thompson, same as you have pictured, and the oddest thing was the “recoil” of it. It felt really strange, not a kick or even push backwards, more of a Bouncy feeling, like it was connected to you with springs. We fired my cast RN bullets thru it with no problems other than it was brand new and the bolt recoil spring was very heavy, it would occasionally short cycle and not pick up a round. And pulling back the bolt was hell on your hand, ended up using my gun belt to pad my hand to cock the thing, but this started getting better after a few hundred rounds. And it weighed a ton! He got the steel receiver version, other than a 50BMG rifle this is the heaviest gun I’ve ever fired, gives me a whole new respect for our WW2 soldiers lugging one of those across Europe!

  4. I had the opportunity to fire a Thompson one time. This particular Thompson that I fired was a legally owned fully automatic firearm (the owner had all of the proper NFA paperwork and tax stamp). I only fired about 10 rounds of hardball ammo with it and I was impressed. I never fired or reloaded ammo from it. Speaking of reloading 45’s, I reload 45’s for all my .45 caliber handguns (mainly 1911’s) and other handguns I own in .45 caliber with my favorite powder, Winchester 231 and use that same powder for almost all my handgun caliber reloading. At one time, 231 wasn’t available and I had to switch to Titegroup or HP 38. Titegroup and HP 38 was a relatively good replacement for 231 and HP 38 was a good replacement for 231 but I prefer 231 for all my handgun reloading except for magnum loads. Winchester 231 is now, once again, back on the market and when it became available again I bought several pounds of it. For magnum loads I use Alliant 2400.

  5. Those two bulged and ruptured cases did not look like over-charged loads but OOB (Out Of Battery) discharges. Over-charged loads’ symptoms usually show punctured primers, popped-out primers and deep indentations on the case head. Just sayin’. God bless and stay safe.

  6. I used to shoot metallic silhouette at the local range. One day I was out with a friend shooting the big bore pistol silhouettes (50 – 200 yards) also the rifle silhouettes were set up with the same range ( 200-400 yards). I was on the lower tier benches and 2 men were above me with scoped high powered rifles. I shot all my targets on the pistol range and was waiting for the 2 men to hit something, I figured while I was waiting I would take the Thompson and try to hit the rifle rams at 400 yards. My Thompson has the peep sight and also the ladder sight for longer distances. I sat on the ground, knees bent with my elbows resting on my knees and tried a shot. It took about 8 seconds for it to hit the target, so I did it a few times more just to see it wasn’t a fluke, It wasn’t A minute later both men came down and saw what I was using and were shocked. They didn’t believe that was possible to do what I was doing. So I had to show them! No problem.

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