I have the Saddle ring carbine in .357, basically the same gun.
I bought some parts from Steve's gunz and Jackfirst.
I bought a new stainless mag spring and cut that down about 6 inches,
a new stainless mag follower, a new and slightly more robust
ejector collar (the original split in half).
With the new cut down spring I can fit 9 .357 cartridges in the mag tube.
Smoothing out the loading gate ports sharp edges helped a lot, it sliced my finger
the first time I loaded it and I didn't even feel it.
I also plugged that goofy safety because I really didn't like that.
Remember to use RNFP ammo for easy feeding.
When you take yours apart you will see that it will need stoning of
all the rough and sharp surfaces.
Hope this helps.