Right hand twist.

[Dave]

I recently saw a display of the two Thompsons used in the St.Valintines killing in Chicago. They are in the custody of the Barrin County MI. Sheriffs office. (one of the killers lived there). They were traced by ballistic testing of the bullets and case markings. (some 150 rnds. were fired). The test procedure was a new thing at the time, 1929. In a written report by the Chicago police dept. it states the Thompson had a right hane twist and only two guns "at the time have right hand twists, the 1917 Army ( S&W I think)) revolver in .45 and the Thompson. This surely is not correct, is it? Could it be a typo meaning left hand? What is the twist on these two guns?

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[Art]

I don't know the twist on the Thompson or the M1917 pistol, but I know the U.S. M1903 rifle has right hand twist rifling. That's one of those statements I think folks throw out there without checking. There were a lot of rifled firearms in the world and I'm sure there were more than 2 or 3 with right hand twist rifling.

[ohiosam]

The home page of this website has a photo of an 1889 Schmidt-Rubin. They have RH twist bbls.
Maybe they meant .45s with RH twist.

[Jim K]

The TSMG has a right hand twist, as does the S&W Model 1917; the Colt Model 1917 has left hand twist, and so does the Model 1911 pistol and its Colt commercial version.

There were a few other guns at that time in .45 ACP with a right hand twist (the Luger test pistols for example), but in practical terms the statement was correct at the time.

The rifling twist analysis was icing on the cake anyway; the place was littered with .45 ACP cartridge cases obviously fired from Thompsons.

Jim

[Dave]

Yes, the report stated that the cases were traced to the individual, two, Thompsons. One had left a distinctive mark from firing pin on gun #2347 and ejector from gun #7580. Looking back at the print out one gun fired 20rnds. and the other 50 rnds. An average of 10 rnds. each dead man. The Chicago "Mob" was always very efficent!

The Deputy who was watching the disply told me they were allot of fun to shoot.
Another point; Report stated the cartridges were all from the US Catridge Co. and "they were manufactured only between July 1927 and July 1928". So the guns must have been in the original Thompson .45 cartridge, which is longer then 45 ACP?

[Jim K]

No, they were Model 1921's in standard .45 ACP. The manufacture date range was determined by the type of headstamp. One gun had a 50 round "L" drum magazine, the other a 20 round "stick." One gun had originally been purchased by a deputy sheriff with mob ties ("only cops should have guns" department), the other by a mobster from the Peter von Frantzius sporting goods store in Chicago, reportedly the source of many crime guns. (Frantzius later was known for his extensive line of plastic handgun grips, sold under the trade name "Franzite.")

Jim

[RCS]

cartridge on the right is the 45 Thompson with 250 gr bullet and with a headstamp of REM-UMC 45 ACP

[Pete]

Right-hand twist is the standard for U.S. field artillery tubes and for that reason drift is always a left correction.

[Dave]

Very interesting, thanks guys. I have one of those Rem.-UMC 45 thompson cartriges. The bullet has more of a tapper to the end rather ten the round bullet on the regular .45 ACP. It can be seen in the picture above, by RCS.

[Jim K]

The M1923 TSMG for the .45 R-T cartridge used the longer (front to rear) box magazine previously developed for the shot cartridge. While the same top to bottom length as the Type XX (20 round) magazine, the recommendation was to load it to only 18 rounds of shot cartridges to prevent the spring tension from crushing the paper shot containers of the shotshells. Those magazines are marked "for shot cartridges" or "for 18 shot cartridges." I have never seen them referred to as Type XVIII, but it would certainly be in line with the designation of other magazines.

The magazines made for the .45 R-T round are the same as for the shot magazine, but do not have any marking on them.

Neither the shot cartridge nor the .45 R-T round will fit in the drum magazines. The guns will work with the special box magazines because the standard box mag does not entirely fill the magazine space as the drums do, so a slightly longer (front to rear) box mag will fit. The use of shot cartridges was reportedly unreliable, though they would function the gun.

(Much of the above and in my other posts was obtained from "Thompson: the American Legend" by Tracie Hill, plus my own knowledge of the guns from owning and firing them.)

Jim