Most 25-20 components seem to be seasonal items. I'd been looking for 25-20 brass for about two years without finding any. I found some at Duck Creek five or six weeks ago and picked up 150. I just looked now and they don't show any. Apparently Winchester ran a batch recently so hopefully you can find some. Hornady 60 grain flat points were scarce for a while but I see them for sale now. Lead bullets are never a problem. Factory ammo is scarce, but around. You'll pay about $1.25 a round though. Starline sells 32-20 brass and I've read of people necking it down. I've not done that, but I do neck their 357 brass down to 256 Win mag without too much problem.
Good luck. It's a fun round. When rimfire ammo was so scarce a while back I shot lots of lead bullet 22 magnum type velocity rounds for very cheap.
