You might want to try these for a low cost plinking load. Seat them flush with the case mouth over a couple grains of Bullseye, then dab a little liquid alox on top for lube.
I shoot buckshot round ball loads in my Cadets and they have a surprising amount of wallop.
I've been using a 93gr LBT mould for mine, and some AA9 powder. 32long Colt are short, but, will work in them as well. They are fun on gophers, and are a really sweet handling gun. The one I have is an H&H, that was built in 1887, a side lever break action.
I sold my Rook rifle about 20 years ago. It had been rechambered to .357 Magnum. Not as nice as yours but one I still miss from time to time. Congrats on getting that one.
I just bought a Westley Richards falling block 300 Rook. I have bullets inbound as well as Bertram brass. I have not shot one but would love to hear about your experiences, you load data etc. Better tomorrows and Merry Christmas! Mims (AKA Harry)
Tex, I dunno what you're planning, but the old Rook guns were somewhat surprising in velocity with BP. If you load black, let us know what it's doing. The .297-250 ran in the mid to high 1300 fps range.
I am..........disturbed.
Concerning the difference between man and the jackass: some observers hold that there isn't any. But this wrongs the jackass. -Twain
Think my biggest concern about black is cleaning, since it's a Martini Cadet pattern and you can't clean from the breech with a normal rod. Not real crazy about trying to clean a BP gun with a Bore Snake or similar widget.
I own a bunch of clean-from-the-muzzle guns. 'Tain't no big deal. fit a rod guide to the muzzle and all is well. When cleaning a Martini I drop the breech block/trigger assembly out of the receiver first for ease of mopping up blackpowder residue. Easy peasy.
"You can lead a man to logic, but you cannot make him think." Joe Harz "Always certain, often right." Keith McCafferty
The research I've seen suggests that the load most folks use is either 10gr of blackpowder, or 4.5gr of Unique under the 80gr RN lead bullets. I'll just have to see how it shoots and how close I can get it to the fixed sights. Mr. Potterfield didn't have any useful info related to shooting it.