from the old forum:
I am curious as to which bullet lube you would recommend. I am presently working on loads for my .357 mag in my Marlin 1894 and .375 Win in a BB94. So far, the Winchester has proven tough to get to group and even tougher to keep free from leading. I have been using LBT Soft Blue. Bullets have been cast from WW and air
cooled then sized .002 over bore. The .357 mag shoots well using a SAECO 170 grain GC bullet and 10.5 grains of 2400. The .375 win shoots well using duplex PB loads and SPG lube but any attempt to push a smokeless load over 1500 fps with even GCs starts leading badly using LBT Blue. So, until I can order a mould from you, do you have any lube suggestions that might help.
Regarding lubes, the best you can hope for is that good lube may make a good load a little better. If your gun has a serious problem, the lube is not going to fix it.
My Marlin 357 isn't fussy about lube. That doesn't mean it will shoot all cast loads well, it just means that it shoots all cast loads about the same regardless of which lube is used. It definitely prefers heavy bullets. At the moment, my Marlin loads use Rooster HVR. HVR picked up 15 fps or so compared to soft lubes, but there was no difference in accuracy.
The 375 Winnie has a long and grossly oversize throat that is rough on cast bullets. You are not the first person to run into problems with the 375. You may have a heck of a time finding a full throttle cast load that is accurate, and that cycles and feeds. HVR seems to be the most likely to succeed, but I'm not going to lie to you -- you're probably going to have problems no matter what lube you use, due to the stupid throat.
I've seen lube make a big difference in revolvers, and I've seen lube make a big difference at 2700 fps, but I haven't seen lube make a big difference at 1400 - 1800 fps in rifles.