Jeff,
I have it from German Salazar that the "magnum" designation in the Russian primers refers simply to cup strength, not priming compound. The priming compound is the same in both the LR magnum and LR -- just as with the SR and SR magnum.
I *think* German remarked that all the so-called "Russian" primers have the same manufacturer; he likes them quite a lot.
I've found happiness with the standard Russian LR primer in the BooBoo size case with H-4831-SC. Just out of curiosity, I tried them in a .338 Lapua size case (really, the .404 Jeffery necked down to .338), and had one "bang" and one "click-bang," but the case was pretty empty with only 79 grains of 4831, in a case that will physically hold 111 grains of 4831 -- that is not a load, just a capacity. BTW, the 79-grain charge of 4831 in that case works quite well with a Winchester WLR primer, though velocity is a bit low.
From the "what some guy said" data bank, the Russian primers apparently need to be seated pretty firmly. I am a bit surprised they don't work well for Baron with Rel-25, which usually lights off pretty easily, but again, that's a case with over 100 grains water capacity. The Boo is about 88 grains H2O, and the .338/404 holds 114 grains water.
Other "what some guy said" data is the cups may be a little short, so in some cases, with some firing pins, the hit is not firm enough, even with firm seating.
IIRC, you're down around Boo size case, Jeff. There is a fair chance they will work very well for you.