I load 6 grs of Trail boss im my schofield loads i use them loads in my keeper 45 schofield 1st and second model.
They can shoot under 3 inch groups at 25 yds to

I just got another first model one of the very first guns made by S&W Serial number under 50
Im gona letter the gun before i go shooting it. they only made 3000 or so first models.
I think the Schofield revolver is top of the food chain in break open action antique hanbguns. The Latch system is way stronger than anything else.
maby 5 grs would be a good starting point in a WG as they list 6 grs for the 45 colt as a max trail boss load in old guns in your soild frame gun the 6 should be ok but again try 5 first and the presure built up will have alot to do with the type of bullet you use.
I also load 5.5 grs of unique this is all with a .452 Keith 250 gr SWC bullet as schofields have tight bores in a WG you might want to use .454 SWC keith type. as the bores on your guns will be bigger than and orignal S&W schofield.
I just got a S&W DA converted to shoot 45 schofield its a long cylinder model gun i cant wait to try shooting it with a Trail boss load.
I like trail boss because you have a nearly full case of powder with 5 or 6 grs and its presure is spread out over a larger area of the chamber. it smells good to
Also keep in mind the new 45 schofield starline brass cases are alot stronger than the orignal brass made 120 + years ago now its soild head brass, i still only reload my cases about 10 times then toss them out.
This is what i use in my guns and have no extraction trobles or any signs of presure.
I know Jethunter has some WGs that cycle and shoot 45 schofield he has posted alot of info on that load i think.
He has some very good bullets to.