I see in stock at various places, Jamison brass in calibers like 40-70 Sharps Straight, 40-72 Winchester, and 35 Winchester, that could be formed and trimmed to 30-40 Krag length.  35 Win would be the easiest, might need an intermediate 8mm die of some sort.  A bit rich for me at nigh a buck and a half each.  The .070 thick rim of the 40-70 might be a bit much for some rifles.  Jamison has an online store of their own too.  (You need to Login to view media files and links) Hmm, 405 Winchester at a more reasonable price.  I have made 6mm/30-40 Ackley improved from Hornady .405.  I made one, sold the rest of the brass, I saw it could be done, and without fancy forming dies.

With PRVI .303 I used the rifle to size them down.  I posted the info above for those who just gotta have the full length case, and those with deeper pockets than I have.  One of my big studies when going to college in the 90s was Nonte's book on cartridge conversions.