For the RCBS bullet (#25-85-CB).......I used the Ross Seyfried blackpowder equivalency formula with IMR-4198 to arrive at the usual 1400-1450 FPS of that era. It states that you take the nominal blackpowder charge weight (20.0 grains) and multiply that by 0.4. 20 x 0.4 = 8.0 This 8.0 grain load produced ~1300 FPS and shot pretty well. With the PROPER PRIMERS FOR THIS CALIBER--Remington #6-1/2--this kinda-slow-for-application powder burned fairly clean. I cannot over-emphasize the uptick in consistency and accuracy you get from the #6-1/2 primers in these small rifle calibers. IMR-4198 has done some really good work in this caliber--11.0-12.0 grains underneath those Speer 75 FPs really shot well for me. It does similar work at those weights with Lyman #257420 (12.0 grains) and #257312 (11.0 grains).
Some other data on the 25/20 is found in a 3/91 edition of the Hercules "Reloader's Guide" (pp. 44). The 86 grain Remington exemplar got 1340 FPS from 8.0 grains of 2400 (18,300 CUP) and 1460 FPS from 11.5 grains of RL-7. CCI 400 primers were used here, which IME are significantly hotter than the Rem 6-1/2s. Both of these loads worked decently with "420" and "312", though mild. Both loads shotgunned the RCBS plain base, but 7.0 x 2400 restored order to the world and 6.0 grains is my 1100 FPS load.
And now--more ancient history for your edification, this from the Winchester "Reloading Components Manual" dated 1995, pp. 41. 3 bullets are listed, and one powder is used--WW-680. That gives a clue as to the era we are examining. No primer characteristics are listed. 60 grain "OPE" shows 13.0 grains of fuel for 2300 FPS and 26K CUP. 86 grain "Lead" lists 11.1 grains for 1895 FPS and 25.5K CUP. 86 grain SP has 11.0 grains for 1800 FPS and 23.5K CUP. Dunno if I would run these in older slide-action rifles, I don't in my 27-S. Win 92 or Marlin 94 should be fine, though. Some kind of rifle primer is indicated IMO, for cup strength at least. Maybe small pistol magnum. The Rem 6-1/2s were so instantly better in several calibers for me I stopped messing around with anything else 10 years ago+. WW-680 runs pretty close to the now-available AA-1680, according to those who know both fuels.
Brass life can really suck in 25/20 chambers. My 1990s-made 1894CL is "chambered long", with a shoulder ahead of where SAAMI claims it should reside. This is a feature of these late 80's-early 90s rifles, and they are not alone in that regard. Care should be taken to not set the shoulder back significantly during the resizing process. I handle this in one of two ways--partial full-length sizing in the F/L size die, or neck sizing with a 25 ACP sizing die. I set the decapping rod at the proper depth to kick out the spent primer while sizing the upper 2/3 of the case neck. The 32/20 has similar chamber poetry, so I would assume that 218 Bees share that personality trait. You can figure on having rifle-specific lots of brass if you own more than one of these creatures.
Other fun factoids......some throats in these calibers don't get along with some bullets, especially leverguns. The bullets' front drive bands collide prematurely with the abrupt leades present in these rifles. You CAN do the right and proper thing, and have the throat and leade relieved and tapered like a self-respecting modern bolt rifle would do.......but what fun is that, being proper and meticulous? NO, BY THUNDER--trim that brass back to ~1.275"-1.290" like a respectable rimmed magnum revolver cartridge does and carry on. You choose.