Scott,
I did quite a bit of shooting with the .25 Hornet a few years back.
It's the .22 Hornet case blown out to .25 cal. as you might have guessed.
The only info I ever found....... admittedly I didn't look all that hard..... is in one of Ackley's two vol. set of "Handbook for Shooters and Reloaders". Page 327 Vol. I.
It's strictly a wildcat cartridge so you'd be pretty well on your own outside of Ackley's work. Not really an awful lot there. The only powder listed is for IMR 2400. with 8 & 11 gr. loads for the 60 gr. bullet, 6 & 10 grs. for the 86 grainer. MV's run from 1525 fps to 2035 for the 60 gr. & 955 to 1675 fps for the 86 gr., using the standard 1-16" twist.
The case has a very shallow neck, similar to the .32/20, which makes it almost a straight case. Ackley says that a load of 12.0 grs. of 2400 and the 67 gr. bullet will give a MV of 2000 fps with very low pressures making it suitable for weak actions such as the Ballard.
Never did any hunting with it, but it's more than accurate enuf for animals as small as head shots on Squirrels out to 100 yds. or so with hard cast bullets. I had mine set up on a Win. Low Wall. It's kind of my switch barrel gun, thus the "had".
If I can be of any other help let me know!
PETE