A look at a Ruger in .44 Magnum and in .45 Colt Comparing Performance Levels
CALIBER
POWDER CHARGE
BULLET & WEIGHT
VELOCITY
PRESSURE
44 Magnum
24 gr. H-110
250 gr. Keith
1528 fps
39,600 psi
44 Magnum
21 gr. H-110
318 gr. LBT GC
1354 fps
44.000 psi
45 Colt
29.6 gr. H-110
250 gr. Hornady JHP
1587 fps
40,000 psi
45 Colt
25.2 gr. H-110
315 gr. NEI cast
1357 fps
40,000 psi
The 250 gr. Hornady JHP in the .45 outran the 250 gr. Keith a bit and the pressures are about the same. So what? And the 315/318 gr. slugs are running practically identical velocities with the .44 only showing 4,000 more psi. So what? Now look at the pressure barrels for each caliber.
The .44 Magnum pressure barrel in the above test was 10" in length.
The .45 Colt pressure barrel in the above test was 5 1/2" in length.
Whatever the .44 Magnum will do, the .45 Colt will do with roughly 1/2 the barrel length, pressures being nearly identical. From the limited pressure testing we have done, we have found that whatever the .44 Magnum will do, the .45 Colt will duplicate with about 5,000 psi less pressure. This is with standard bullet weights. As the slugs get heavier the gap widens.
An interesting point to note is the .45 Colt holds about 4 to 5 grains more powder than the .44 Magnum. Our load/pressure data proves this difference while pressures remain comparable. But you can see the .44 has to work 4,000 psi harder than the .45 to move a 318 gr. .slug at the same speed, this even discounting the drastic difference in barrel length.