Which mould will my rifle prefer?

I have been experimenting with cast boolits in a couple of single shot rifles. The one I have been giving most attention to is a Henry single shot in .357 MAX. But I also have a single shot Ruger #3 that started out as a .45-70. I had it rebarreled to .375 JDJ. It is impressive with J-word boolits but it kicks this old man too hard. So I decided to try cast boolits in it. The first mould I got was a Lee 250 grain flat point gas check. I have loaded up some of them with different powders with good results. My original goal was to reach something like 2,000 fps with this boolit. After studying load data and reported results for the .38-55 and the .375 Winchester I have decided that my goal should be reduced. New goal is to be in the neighborhood of 1,500 fps. Better for the shoulder and entirely enough for lower 48 game animals.

Since starting with the Lee boolit I found an RCBS two cavity mould that throws a flat point gas checked boolit to about 250 grains. So now I need to cast up some boolits and try them. I have a pretty good selection of powders.

Does anyone here have a recommendation regarding powder, amount, or which boolit they think will do better? With the old criteria I was casting the Lee boolit with Lyman #2 alloy because I thought 2,000 fps required it. I am using Carnauba red lube. Since I cut back velocity maybe I'd be as well off with a COWW alloy. I have yet to see a sign of leading.

Thoughts, anyone?

I can only reply with my experience with my 38/55 shooting the Lee 250 gr. Which vita my alloy is only around 240. Anyway, tried quite a few powders, 2400, 4198, 4227, benchmark, 3031, red dot & unique. Settled on 5744, around 23-24 grs. This was the most accurate load I found. Shooting this in an Encore with MGM barrel.

I would use a much softer lube and 15/1600 will work well with 50-50 WW /lead Ed

It's not up to us or even you. it's up to the rifle. I'll suggest buying small orders of commercial cast bullets before investing in more molds.

I haven't finished the rifle for it yet, but I got the Lyman #375449 265 grain molds for a 9.5x57. This cartridge is nearly identical to the 375 JDJ in capacity & performance. Norske has a good idea: buy some different cast boolits and try them out. The one that shoots the best wins the contest.

2nd on the Lyman #375449, best accuracy for full power loads with cast in either Win 94 or Win 1885 is with IMR3031. I use a load from the the Lyman #4 Cast Bullet Handbook.
Hornady Gas Checks too.

For lighter stuff I use the #375248 over Unique from the old Lyman #2 Cast Bullet Handbook.

I use White Label Lubes BAC for both loads.

I like the RCBS 300gr fp cast for 45/70 and as others have been mentioned the Lyman reloading manual will give you good loads, I also use this cast bullet in my458 WM with 18gr Unique and it shoots better than I can. My 357 Maximum built on a Martini will shoot cast into 1 1/4'' groups all day at 100 yards, it quiet likes the Lee 158gr R/F over 20gr H110 as a top end load and anything under that also shoots really well. I cast my own and size to .360 and find anything under that is a waste of powder, fit is everything with cast. Regards Stephen

Firearms are somewhat like women, they are all alike but different and each responds to different things. If you want to know if something will work well for your's, try it.

I am familiar with the rcbs 37-250-fn, but I use it in a couple of .375 H&H ‘s ( each with 1:12” twist) and have had excellent results accuracy wise. I also use Carnuba Red lube with no problems. Just my opinion but I’d go with a softer alloy than the Lyman #2 if you are hunting. Only killed one smallish n. Texas deer with this boolit, but he expired without voicing any complaints. To give some idea of the high lead content of the alloy I use with these; they run nearly 280 grains as cast.