Hard to find ammo for? It is, and always was, a necked-down 45/70... I have shot mine lots with a mixture of .33 wcf, and 45/70. It was a lot of gun in 1907, and still is. I never figured out why the 30-30 model 94 lasted all these years and the .33 model 1886 didn't. The '86, IMHO, is a far superior rifle, and one of my all time favourites. My .33 was made in 1894 (S/M 93,###), but was shipped back to the factory and re-barrelled, which was a common practice for a while, after the introduction of smokeless powder.
My grandfather carried a .33 for 50 years (my cousin inherited it, the bugger) and my dad used to tell a story about Grampa meeting an old native guy in the bush one day. The native guy checked out Grampa's .33, then dismissed it as being too small of a bullet. Grampa suggested they shoot into a tree, and compare. The native guy popped 45/70 into the tree, went over, put his little finger into the hole and proudly showed that the slug had gone in almost to the third knuckle. Then Grampa popped one in with the .33. The walked up to the tree, and the guy started laughing, "no hole, white man missed tree". Grampa said "look around back". There was a slab of bark about 2 feet long missing, where the .33 had passed right through. Native guy said "hrmph", and went home. Family folk lore...gotta love it!