44 Spl guns and SBH guns take two different diameter cylinders; 44 Spl is a mid size and SBH is the full size.
Easiest way to get a mid size 44-40 cyl is to obtain a used mid size .357 cyl, either old or new model will work, about $75 to $100. Buy a reamer from Brownells for $135 and ream it or have it reamed to 44-40.
Remember both 44S and SBH barrels have .429" bores so additionally, ream the 44-40 cyl throats to .429" and use .429" or.430" bullets for decent accuracy.
Easiest, and what I did for my SBH was pick up a used 44 mag cyl, fluted or smooth. You can also use a used full size new model 357, old or new model 30 Carbine or 41 Mag cyl (but they will all be fluted), and have reamed, again with .429" throats.
The 44 Mag cyls are easiest to ream and can be done by hand because hardly any material is removed and that's the only way to get a used smooth cyl to make your 44-40 cyl. Also the throats will already be .429". Some will be quick to tell you that a 44-40 reamer case neck is smaller than the 44 Mag chamber neck size, which is true. However, since you must use .429 bullets in the 44-40 cases, the 44 Mag neck size will work to your advantage. I get great accuracy with mine.
When buying an extra cyl, you want one with the same or longer overall length as the cyl in the gun now.
Other options include custom cylinders that start at about $300.
