Can't speak to the usefulness of tumble lube for your application, but my gut questions the efficiency of such a long slow bullet in a 1-10 twist. Didn't the .25-35 with a long 117 grain bullet (at much higher velocity than a .25-20 ) utilize a 1-18" twist?

I purchased the Borton mold from a forum member. I think Match Results indicate some shooting this weight bullet with 25-20 SS and 25-20 wcf in Quarter bore competitions. Nice looking bullet. I will pan lube some and will know in a few days how they do. I made 200 cases from 223 (what a time consuming project). Looking at the amount of effort now should have sent SSDAVE funds for some Jamison like I used for my R2 Lovell.

gnoahhh wrote on May 3^rd, 2026 at 8:01am:

I tried lee tumble lube  breech seated. Mind you, this is in my 30-06 Ruger #1  which isn't the most accurate but shoots best breach seated with cast bullets over fixed ammo. Everything went good for about 50 or 60 shots.Then I could barely push a bullet in and shots all over the paper. Leading  was severe in two inches forward of the throat.
This is only one instance , but that was my experience.

Tried Red Rooster  clear lube. Throw 100 bullet in a plastic bowl,swish around and dump on wax paper.....Will sell bottle CHEAP !   Back to Javalina lube and stick with it...period.

I believe tumble lube works pretty well on low velocity pistol bullets. I used 45-45-10 on hundreds of 45ACP bullets when I was shooting BE pistol. Also on 32&38 WC. It worked perfectly. 
I’ve tried it on 30 cal rifle bullets applied in addition to my regular lube. I can’t say there was any benefit there.
For rifle length barrels and higher velocity, I'm pretty sure leading will be a problem.