Introduced in 1979, Winchester had been working toward standardizing the 45 Winchester Magnum for two years — as noted elsewhere in these discussions, things in the gun industry tend to run at positively zephyric pace, snails often move faster! This round comes oh-so-close to reproducing the similar round Remington developed in 1923, the 45 Thompson. Ballistics are very similar as is everything else. The Winchester version has a significantly longer case and is loaded to somewhat greater length. I have been unable to determine what pressure Remington intended to load the 45 Thompson round at but, according to the ballistics claimed, it had to be close to the pressure Winchester standardized for its version, 40,000 psi. The 45 Thomson failed for the simple reason that a heavy bullet that would significantly extend the useful range of the 45 Thomson submachinegun also generated so much recoil the gun was practically uncontrollable, even in the hands of a well-practiced expert with the Thompson chambered for the standard 45 ACP. Conversely, lighter bullets, loaded to mitigate recoil lost velocity so fast that ranging-potential was not significantly improved and recoil remained an issue. It just did not work. Winchester designed its 45 Magnum for chambering in the Thompson/Center (T/C) Contender. It worked perfectly in that application and did exactly what Winchester hoped it would do, duplicating performance of the 44 Magnum, which is exactly why it was an abject commercial flop. Why would anyone buy a 45 Magnum barrel for their T/C when it would do nothing the 44 Magnum would not do, used a rimless case that made loading and unloading the T/C more tedious, and had limited factory-load options (while everyone made a variety of 44 Magnum loads)? Perhaps Winchester hoped other companies would pick up on the 45 Magnum and chamber it in other guns but that never happened commercially and the round just quietly died. Regardless of that, the 45 Magnum offers significant performance and with the right bullet it is a fine hunting option for the T/C. As noted, it will do anything the 44 Magnum will do and, where bullets can be seated out to a longer overall length it will far surpass performance of a 44 Magnum revolver. As with any pistol round, best practice is to apply a taper-crimp after seating the bullet. This helps to lock the bullet in place and eases chambering. I cannot too-strongly recommend getting a second seating-and-crimping die so you can have one adjusted to seat the bullet and the second adjusted to only taper-crimp the case mouth. Generally, attempting to do both operations in one step is a recipe for damaged and destroyed cases. This is merely a longer version of the case used for the 45 Automatic, the heritage of this case dates all the way back to the 40-70 Ballard of 1873.