In certain situations there is a case for having a .45 round with a bit more power than the ACP or the 45 Long Colt. This would be as a 44 magnum is to the 44spl. A friend of mine often suggests reviving the .45 Thompson load. To quote a very nice site on the Thompson.
"An interesting development of the year 1922 was the Remington-Thompson .45 cartridge. This had a case or shell about one-eighth inch longer than standard, that it might not accidently be fired in a .45 caliber pistol. Results would have been disastrous because of the excessive pressure. This Remington-Thompson load -used a 250 grain bullet driven at a muzzle velocity of 1,450 f.s. It had a penetration of about fifteen boards (of Pinewood) at the muzzle, and better than eight at the 300 yard mark. However its production was abandoned when it was found that the accuracy was not as great as that of the 230 grain standard load, and its 1050 foot pounds muzzle energy as against 430 foot pounds for the standard load did not appear to deliver the increased shocking power which was expected of it. Guns using this cartridge were never sold commercially, although very complete tests were run by the Auto-Ordnance Corporation"
The lack of increase shocking power is no doubt due to both rounds using FMJ ammo. It is not how much energy a round has but how it applies it. Such a round with modern hollow point ammo would show a marked improvement. Another idea occurs to me, however. Shooters have found that shotshells made from .30-06 brass can be used in .45 ACP revolvers such as the M1917s. The brass from .308 and other rounds may also be utilised. The possibility exists that a potent round could be made by mounting .45 slugs in 30-06 casings. For obvious reasons I call this round the .45 Springfield Magnum. My friend Ed suggests ".45-06"
Such a round has several applications:- It would be a good round for a survival handgun, offering the user both hunting and self defence capabilities. Shotshells can be used against small game while deep penetration rounds can be used against larger animals. A revolver configuration offers advantages as a defensive weapon against dangerous animals. It can still be fired when the muzzle is in contact with an attacking animal, and can be fired submerged in the event of crocodile/alligator attack.
A revolver loaded with .45 Springfield Magnum would also make a useful bodyguard weapon. A revolver can keep firing if a round misfires, and the increased case size allows the user to tailor the charge to the maximum that he can rapidly fire. Such a weapon will probably have a laser spot and a tailored grip. Some of the chambers might be loaded with OOO shotloads.
The .45-06 round might be suitable for use in large framed automatic pistols such as the Desert Eagle. Another idea is a Mauser broomhandle type weapon maybe using AR-15 parts. The round may also see use in lever action carbines.
UPDATE The .45 Super® round offers a 22% increase in velocity and 50% in energy in a round externally similar to standard .45ACP. This mainly seems to have been done by improvements in case strength. There have been other increased power .45s. The .451 Detonics Magnum could be used in a pistol of conventional size, while the .45 Win Mag was used in the large Widney pistol and Thompson Contender pistols and was made from trimmed .308 brass. Possibly by using rifle brass a round of even greater capacity or heavier bullet loadings could be created, especially if a revolver or Mauser type configuration is used and the round does not have to fit in a pistol grip. A case of 32mm or longer should be possible. The .44 Magnum and .45 Colt are included for comparison. Bullets of up to 300gr are available for the .45 Colt and could be used with the .45-06.