Some really interesting & quite useful cartridges become moribund in
their infancy. I'm thinking that the .33 Winchester was a victim to faster cartridges, better marketed rifles, and the buying trends of hunters way back begining of the century past.
No one squawks and squeals that the venerable grandfather the .45-70 Govt. , is a non relevant has bin relic. Well, cold day In Fiji before you find any .33 Win. ammo or cases on the shelf. 
Just so happens, I was cleaning and found two complete 1871 actions, and I even made a trigger gaurd mold, and cast some spiffy
Trigger gaurds. It's a single shot, and it's a piece of history. 
I even have an Ideal 1930s mold. 200 grain flat point.  
Not exactly metallic rear aperture friendly, but I am sure some clever
fellow will come up with a way to dress up a long barrel.
And since New York State (gorgeous land), has turned most of the state into rifle hunting, go figure how that happened, I'm going do this project. Any thoughts, suggestions & commentaries. 200 grains of lead at 2000 fps goes a long way.

All of my handloads for the 1871 Mauser prior have been safe and well below pressure limits established for the 1871.
I used brand new 45-70 Cases reformed to .33 Win. 
200 grain lead cast, (soft).   
It's a slowster, accurate & mild recoiling.
150 yard if you are a good marksman.
Typically where I hunt, I shoot deer 50-75 yards. 
33 Win is a 120 year go back in time round.
Suits me just fine.

It really would be a lot more fun if we could shoot them, and have 
someone clean them for us. 
For 150 year old guns, black powder is the safer way to use them.
Some enterprising youth would make some money cleaning BP guns
For old guys.
2 hours of shooting and two days of cleaning.
Gee, how can so much fun turn into so much work?

So, lemme understand here. . .you're thinking of putting a .33 Winchester barrel on a Mauser 71 action?

The 1871 Mauser action was used by the Uruguay navy chambered in a smokeless powder 6.5mm cartridge. I would think m ost of the late 19th century military 6.5mm cartridges operated at 40,000 p.s.i or more so moderately loaded 33 Winchester smokeless rounds would probably be safe. It probably wouldn't hurt to get a little more feedback from some of the gunsmiths and ballistic experts who frequent this forum.

Come to think of it, one of my 71 Mausers was originally barreled to the 6.5x53.5 French Daudeteau (not to be confused with the 6.5x53 Dutch/Romanian Mannlicher). With only the bolt handle serving as the locking lug and the confusion with the loading data I'm glad I had the 8.15x46R Aydt barrel put on mine and never even considered going the 6.5 route. There also seems to be quite a bit of discussion about the "banana" effect of the single lug being on the side of the bolt and the less than great accuracy that causes for the 6.5s (not a problem for my 8.15x46R or the 11 Mauser).

My appologies, I forgot something.
Brand new still in the cardboard box, Ideal (Lyman) single cavity 
.338320 mold. 1930s.    It's even a GC little critter.
For all of you wondering how fast  I  am going to load the ammo for 
The. 33 Win., well, that I can not tell you at this very moment. Slow is the operative word here. Going be a black powder cartridge extravaganza.   

Be good to see it when it’s up and running 
Gumpy