Opening post questions:
cartridge
The Thompson submachineguns and the 1911 Colt Automatic use the
same .45 ACP cartridge.
punch
The longer barrel of the 1921, 1928 and M1 Thompson 10.5" versus
5.5" for the 1911 gives very modest boost in velocity and impact
energy over the pistol but 10% or so aint bad. They do hit a little
harder.
accuracy
I own a .45 Thompson TM1 carbine and 1911A1 pistol both made by
AutoOrdnance West Hurley. The carbine is a civilian verson of the
WWII era M1 Thompson, but with 19.5" barrel semi-auto only from
closed bolt position. The carbine shoots 6" groups at 100 yds while
the pistol shoots 6" groups at 25 yards, so I would expect the
general run of Thompsons to be more accurate than the general
run of 1911s.
general dust from the belfry
General John T. Thompson was the driving force behind the
development of both the .45 ACP cartridge and the submachinegun
that bears his name.
Colt made 1911 and 1911A1 automatic pistols that used .45 ACP.
Colt made .45 revolvers that used a different .45 cartridge, the
.45 Colt aka .45 Long Colt. Colt also made .45 revolvers in .455 Webley
a British cartridge, and in .45 Schofield a .45 cartridge shorter than the
.45 Colt, and revolvers in .45 ACP and .45 Autorim. At one time, the US
Cavalry used revolvers in both .45 (long) Colt and .45 (short) Schofield.
Can get confusing. There are books on the subject. And experts get
confused as well as hobbyists.
The original 1927 Thompson carbine was a different critter than the
current Thompson 1927 civilian model: the modern version comes in
a conventional rifle version with 16.5" barrel and an NFA SBR version with
10.5" short barrel that requires federal registration. The current 1927 fires
from closed bolt; the SMG fired from open bolt . The original 1927 carbine
was just a 1921 submachinegun with a solid plug in place of the selector
(semi or full) switch and most 1927s were retrofited with 1921 SMG parts
to make them select fire anyway.
There are no internal parts in common between the original 1927
carbine and the current civilian 1927 model.
The 1923 Thompson and its .45 Remington-Thompson cartridge were
intended to compete with the 1918 BAR Browning Automatic Rifle
which served as the US Army light machinegun in WWI, WWII, the
Korean War and into VietNam. The BAR was just simply better in the
light machinegun gun role and shared common ammo .30-06 with
the infantry rifle. 1920s US Army Ordnance liked to keep its supply
system simple: .45 ACP and .30-06.
