choice of brass is limited, I beleive Norma and Lapua are the only makers at this time.
Brass is limited and expensive when you can find it. However, Wolf sells a line of 7.62x54r ammo made by Prvi Partisan with boxer primed brass. For 60 cents a round or whatever they charge, its still cheaper than buying new Norma brass. IMHO, using Norma or Lapua brass in a Russian Mosin nagant is like putting a spoiler on a Ford Pinto.