Found a site, which I can't get to from work to link to because of a silly internet filter... that has a number of Swedish Rolling Blocks in "12.17x42RF"  I assume that means "rimfire".   
I was unable to find any cartridge references at home last night (but I haven't exhausted my references yet).

The prices (around $500-ish) and conditions have me interested...
But I have no idea if there is ANY practical way to convert the block to centerfire (the least daunting part, to me at least) and to form some centerfire brass from something reasonable (the far more daunting part of the equation from my perspective).

Is there some way to get one of these old 'Rollers shooting WITHOUT rebarreling one?  I have a certain sick fascination with finding the really weird ones cheap, and spending an inordinate amount of time and money making 'em shoot. This is a recent affliction, and I'm hoping I come to my senses before too long..

Anyone know anything about making a 12.17x42RF shoot centerfire?
Thanks in advance!
Paul F.

Hate to burst any bubbles, but the .50-70 dies wont work with the 12.17x44 very well. I had this chambering in a Swede Roller and heard the same thing, but it just wont work. Resizing works the brass too much, and the shellholder is different. Best to get the correct dies and brass from Buffalo Arms.
The rimfire breechblock can be converted to CF, so that will work.

Now I'm confused.  The Pettson site was my information source about using 50-70 dies and bullets.  Marlinguys experience was they excessively sized the cases and Paul found they didn't size the brass at all?    Something's rotten in Denmark (Sweden - Norway?)  As for the shell holder, obviously you would need one for the .348, the source of the brass, rather than one for the .50-70.

Jerry Liles

.50-70 brass wouldn't even come close to fitting in my chamber! When I ran one into the chamber after sizing, it still was too large for the chamber. 
I guess I didn't say this right the first time. If the brass is already sized to fit the chamber, it will rattle around inside the dies. If you use .50-70 brass, it's way to large to even chamber in the 12.7 Swede.

Sorry, I am a little late on this one.

I have looked closely at the specs for both 12.17 and 50-70 brass.
The base (not the rim) of 50 70 brass is .557 while the 12.7 is .545.
The 50-70 tapers slightly to .532 at the neck as opposed to a fairly straight .543 for the 12mm.
So with a 12 thou larger base I would not expect a 50 cal case to fit a 12mm chamber.
I quickly discovered however if you take 10 thou off the RIM (which IS too large)  50 cal brass  will fit quite nicely into the 12mm chamber,or at least they have on the dozen or so rifles I know of over here.
Obviously the chambers are fairly generous on the Swedes,and the starline brass may be a tad smaller than the specs.
All the information I have read says this is not possible,but unless I am missing something then I see no reason not to use 50-70 brass in the Swedes.

A few years ago I talked to the dealer in Arizona who was selling the Swede Rollers,  he said a 50-70 reamer would clean up the 12.17 chambers and would sell them original or reamed to 50-70.  I have not worked on one myself.

Gundoc

Howdy
Having had a few of these 12.17 rifles, I have basically done almost all of the above. The 348 brass does work, although the rims were a little small, but worked just fine. Turning the rims on the 50-70 worked also, but they would not go in one rifle. After a while you have to figure the answer is it depends, on the particular rifle. I did have a 50-70 reamer turned in one to cure a bad chamber and open up the rim recess. Worked very well, except for one small problem. The pilot for the bore ended up being smaller than the front of the reamer. We didn't realize this till later, and cut a step in the rifling. Shot great, but leaded at the step something fierce. A coned throater cured that, still have this rifle and it still shoots great.

Tom