I am not offering legal advice. However, my understanding is that you area allowed to sell off firearms in order to enhance or expand your collection. Buying a crate of 20 and selling them off individually to make a profit would probably not be a good idea. Buying a crate, keeping the nicer, unusual, and/or hard to find Mosins and selling off the rest so you can buy more is perfectly fine. Buying a crate with one or two other C&R holders each paying a share for the guns they receive, completely ok.
Anyone with questions regarding C&R purchases should contact the ATF at their Nashville field division (615) 565-1400 or review the helpful FAQ on their website: http://www.atf.gov/firearms/faq/curios-relics.html .