RIC in .450CF - Safe to shoot .455 webley?

[fiscus]

Look at the pressures in those graphs, they are twice as high as what you will be loading and are more applicable to rifles than a pistol. The safest bet for reloading is to work with published data. You can get a lot of info and ideas from loading manuals, get as many manuals as you can. For example the alliant manual lists a light target load for .45 acp that could be used in a .450 cal antique gun: 200gr swc, 1.19 oal, 5.1gr unique powder makes 810fps from an unvented 5 inch test barrel @ 9600psi. They don't have any light loads listed with 2400 powder.

 

[DEZ]

Look at the pressures in those graphs, they are twice as high as what you will be loading and are more applicable to rifles than a pistol. The safest bet for reloading is to work with published data. You can get a lot of info and ideas from loading manuals, get as many manuals as you can. For example the alliant manual lists a light target load for .45 acp that could be used in a .450 cal antique gun: 200gr swc, 1.19 oal, 5.1gr unique powder makes 810fps from an unvented 5 inch test barrel @ 9600psi. They don't have any light loads listed with 2400 powder.

original 450 loads were only about 650 fps

 

[fiscus]

With a heavier bullet and out of a revolver with a cyl gap. That data above is from a non-vented test barrel, at the beginning of the book it even says actual velocities will be lower.

 

[jethunter]

...Has anyone experimented with both 2400 and unique, and if so, what were your observations? For those that use one or the other, I'd also be very interested in reading about whatever your experience was, positive or negative...

I used Quickload to compare 2400 and Unique in .455 MkII case using a 250 gr .455 bullet in a 4" barrel.

Unique: 4.0 gr, case 70% full, velocity 631 fps, peak pressure 11,308 psi at 0.200 milliseconds, powder burned 85%, ballistic efficiency 25%.

Alliant 2400: 8.0 gr, case 85% full, velocity 633 fps, peak pressure 11,303 psi at 0.176 ms, amount of powder burned 44%, ballistic efficiency 14%.

As you can see, 2400 reaches peak pressure earlier than Unique to reach the same velocity in the .455 MKII case, which means that 2400 would generate MORE stress on the chamber than Unique. Quickload does not show that 2400 has any advantage over Unique in this cartridge, and in fact indicates that Unique is more efficient and arguably "safer" due to the softer peak pressure rise.

I think that the advice to use Alliant 2400 as a black powder replacement is based on use in larger capacity rifle cartridges that used FFG black powder and does not apply to most handgun cartridges. Smaller black powder handgun cartridges were commonly loaded with FFFG which is faster burning than FFG and better suited to use in smaller cartridges and shorter barrels. 2400 is not a good replacement for FFFG.