The .45 Colt — often called .45 Long Colt — has been in continuous production since 1872, making it one of the oldest American centerfire cartridges still in active use. It's the dominant cartridge in cowboy action shooting, a capable hunting round in strong single-action revolvers, and a joy to cast for. The large diameter and moderate pressure make it one of the most forgiving calibers for cast bullet work.
The .45 Colt comes in two pressure tiers. Standard loads (around 14,000 PSI) are designed for older Colt Single Action Army revolvers and replicas. Heavy loads pushed by handloaders using strong modern revolvers like the Ruger Blackhawk or Thompson/Contender run at significantly higher pressure — sometimes approaching .44 Magnum territory. Your alloy choice depends on which tier you're loading.
| Weight | Profile | Best Use |
|---|---|---|
| 200 grain | RNFP, SWC | Cowboy action, light target loads |
| 250 grain | Round Nose Flat Point | Most popular cowboy action weight |
| 255 grain | Keith SWC, RNFP | Classic all-around load |
| 300 grain | Flat Point, WFN | Heavy hunting loads (strong guns only) |
Cowboy action note: SASS rules require flat-nosed or round-nosed bullets — no hollow points or sharp-edged designs. The 250 grain RNFP is the standard choice for cowboy action .45 Colt loads.
No caliber is more closely tied to the cowboy action shooting community than the .45 Colt. Serious SASS competitors shoot thousands of rounds per year, making cast bullets essentially mandatory for the economics to work. A competitor shooting 3 matches per month at 100 rounds each needs 3,600+ bullets per year just for matches — and most also practice heavily. High-volume casting is not optional at this level; it's a requirement.
The M2R Automatic Casting Machine handles .45 Colt and all major handgun calibers. Ideal for cowboy action shooters and small manufacturers.
View the M2R MachineNo — they are completely different cartridges. .45 Colt is a rimmed revolver cartridge from 1872. .45 ACP is a rimless semi-auto cartridge from 1904. Both use .452" diameter bullets but are not interchangeable.
Most .45 Colt revolvers run well with .452" bullets. Some older guns with worn or oversized cylinders benefit from .454". Slug your cylinder throats — they are often the tightest dimension — and size to match.