45 “Cowboy” Special

45 Cowboy Special (or sometimes just 45 Special) is a 45 ACP case, with a 45 Colt rim. The 45 Colt rim is smaller than the rim on a 45 Auto Rim. This lets it feed in many cowboy-action guns and use common 45 ACP load data. The smaller case-capacity means better performance with light loads, which is why I am interested in it.

Factory Ammunition

I found a source for factory “American Cowboy Ammo” .45 Special. Specifications: “180 Grain Round Nose Flat Point” at 475 feet per second. I disassembled a loaded round and the bullet weighed 183.5 grains actual, over 4.4 grains of mystery powder. Unfortunately the factory rounds would not reliably chamber in my Ruger Blackhawk 45 ACP cylinder. I believe they were hanging up on the bullet nose. Only about half would fit in an EGW chamber gauge. Rounds that fit would not always chamber. Everything chambered fine in a 45 Colt cylinder.

Firing Record on 3/7/2017 at Sunnyvale Rod & Gun ~ 55℉ outside

Firearm 5.5″ Ruger Blackhawk with a 45 Colt cylinder

LabRadar Series: 68

Velocity: 485fps avg (555,513,526,472,576,347,450,435,488)

Spread: 576 – 347 = 229fps

Std Dev: 69.45 fps (9 shots)

Approximate Drag Coefficient: -0.64 fps/yard

Notes: Very light recoil, very quiet report, but significant unburned powder. Power Factor ~90 or only double the recoil of a .22lr.

Hand Loads

After firing the factory ammunition I uniformed the flash holes on the brass.

Bullets: 165 grain DEWC from Matt’s Bullets (Seated Flush by using an expander die, taper crimp in separate step.)

Primer: Rem 2 1/2

Powder: 0.7cc (Lee Dipper) Trail Boss

Brass: 1x Fired

Firearm 5.5″ Ruger Blackhawk with a 45 ACP cylinder

Velocity: 764fps

Spread: 784-748.5 = 35.5fps

Std Dev: 13.44 fps (6 shots)

LabRadar Series: 71

Notes: Clean burning. Clean holes. Mild recoil, but not recoil-free (~125 PF).


165 grain DEWC from Matt’s Bullets, seated flush, taper crimp. Fired in a 5.5″ Ruger Blackhawk with a 45 ACP cylinder. Velocity in feet per second.
Avg Vel Spread StdDev N Charge Primer LabRadar # Notes
766 799-747=52 20.5 6 3.0 Red Dot Rem 2 1/2 S97 Smelly
764 784-748.5=35.5 13.44 6 0.7cc Trail Boss Rem 2 1/2 S71 Accurate and good holes
591 615-546=68 30.4 5 0.5cc Trail Boss Rem 2 1/2 S99 Smelly
517 554-494=60 32 3 2.0gr Clays WLP S98 “Crackling” burning powder in air. Some holes were not clean. Some shots were silent with no hole, but clear bore.
411 6 3.1 3 1.5gr Clays WLP S100 No crackeling
580 603-551=52 16.9 12 2.0gr TiteWad (3BR #18) WLP S104 Unburned powder in case
467 480.5-452.5=28 14 3 1.5gr TiteWad (3BR #15.25) WLP S105 Unburned powder in case
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