15mm pinfire & 577 "solid" velocities?

[Boberama]

So apparently the "standard" load for both of these was 28 grains of "pistol powder" under a 450-grain hollow-base bullet... in some pinfire loads the charge was even smaller.


So, just out of sheer curiosity...


What kind of velocities do you think these would have?


I've read one source that claims 725 fps, but that seems suspiciously high to me, given only 28 grains of black powder with such a heavy bullet!



I've also seen someone who actually loaded for one, they posted that 42.5 grains of Goex FFFg under a 457-grain bullet gave them 680 fps.





So... 28 grains of "pistol powder"... maybe 600 - 625 fps? Or even lower? What do you think?

 

[Scorch]

Pistol powder was likely FFFg, and velocity was probably below 500 fps. As a comparison, a 50 Remington M71 fired a 300 gr lead bullet at 600 fps propelled by 25 gr of FFg. So approximately same amount of powder, heavier bullet, that pretty much means lower velocity.

 

[Mike Irwin]

Agree. No way velocity was even remotely close to 725.

I suspect 550ish, if that.

 

[Boberama]

A couple more things I've found... this one from some Dutch forum I believe:

Apparently the author of whatever book that photo comes from thought 550 ft/s was appropriate.

As well, some similar bullet weights/charges

40 gr musket powder (FFg?) in the Springfield pistol-carbine gave about 600 ft/s with a 468 grain bullet (1860s ballistic pendulum).

30 gr FFG in the 1855 Harper's Ferry pistol-carbine gave 577 ft/s with a 525 grain bullet (modern chronograph).

However both of those have 12-inch barrels, and it's FFg instead of FFFg. In any case I guess somewhere from 500-600 ft/s sounds about right to me for the .577 from a revolver.




In "The Webley Story", Eley and Kynoch 15mm pinfire cartridges are said to only have 21 grains of powder, I suppose that could put them as low as 450-480 ft/s! However another source shows Eley loaded at least some of their 15mm pinfire with the same 28 grains of powder as the .577 cartridge.


Also I should mention the guy who owns the .577 mentioned in the first post said that he had reduced his loads to 600 ft/s for fear of damaging such a rare piece.