Awright, let's get this party started! One GREAT idea from Molly.
I now have about 400 cases in 25-20 WCF awaiting refill, to service a Marlin 1894CL so chambered. This rifle will shoot LIGHTS OUT with 11.0-12.0 grains of IMR-4198 and the Speer 75 grain flat-nosed soft point, but I don't think that bullet is long for this world. It also shoots well with the Hornady 60 grainer. My idea is to find a load that shoots well with castings--and that has been an elusive goal for 3-4 years.
Progress so far.........these rifles have 1-14" twist rates, which per my experience and that of a few other posters limits their accuracy with longer bullets (80-90 grain) to varying degrees--esp. if "plinker" loads at reduced velocities are the object. I am beginning to think that plinker loads might not be an option in this caliber, but haven't thrown in the towel yet.
I have 3 boolits at hand that are appropriate for the caliber--Lyman #257420 (70 grain GC/FN), Lyman #257312 (88 grain GC/FN), and RCBS-85-CB (85 grain PB/FN). 80% of my cast boolit work has involved the first design, 15% involves #257312, and the 5% tried with the RCBS PB'er has been dismal.
Overall, #257420 has given the best performance so far, and gets better as it gets run faster (to about 1700 FPS) where it "plateaus" accuracy-wise, and stays about the same (1.5" to 1.75" @ 50 yards) to the limit I've run it to--~2000 FPS. Use of neck-sized cases REALLY reduced the flier dispersion, but the fliers still occur--1 or 2 in a 10-shot group, every time. When I see them in a group, I exclude them--which is kinda bogus, really--but 10 shots out of 11 or 12 will stay inside the 1.5"-1.75" @ 50 yards pretty reliably. Tantalyzing.......accuracy just out of reach, it seems like.
#257312 was awful at 1890 speeds (1450 FPS), and improved somewhat as I ran them faster--but not like the lighter Lyman. Further work is indicated.
More work is pending with the plain-based RCBS castings, too. I don't imagine a PB boolit is going to stay real accurate past about 1400 FPS, but I won't know until I try it.
Flier control might mean scaling boolits. I would prefer a root canal, since eyeballed RCBS 6mm x 95 grain castings can do 1.25"-1.5" at 100 yards in my 788 x 243.......but ya gotta do what ya gotta do, I guess. Buckshot and I spoke yesterday at the range on this subject, referring to the one round per group fliers the 243 was throwing at 100 yards. If scaling does the trick, I see an electronic scale in my future.