I'm no expert, but I believe that only SR9/SR9C mags can be used. Checking the Ruger forum may provide additional answers.

OK found out that only the 17 round mags are interchangeable on the SR9 and SR9C, the ten round mags are specific for each pistol. and cant be swapped out. Also none of the other mags are usuable in the SR9C. Since I prefer the 10 round mags when im carrying does any one know of any after market mags made for the SR9C or any retailers selling them for less then the factory does?

Having picked up an SR9c recently I was wondering if it was required to use a spacer on the 17 round mag to ensure reliability. I have a glock 29 that requires a spacer for the G20 mags or it jams very consistently.

its recommended and one should have came with your gun when you purchased it, limits the wobble a bit and makes for easier handling, if your dealer didnt give you one with ur package then you should go back to him.

I received one with the gun, but when I started thinking about getting another 17 round magazine I could not find any spacers for sale.

Go to Cheaper then Dirt web sight, they have them for $5.84 which is reasonable. Also have the 17 round mags for $34.97 which is a pretty good price. If I dont find some ten rounders soon I might just get another 17 round from them.

The 10 round mags froma full size sr9 will work, you just have to change base plates. The fillsize 10 round mags are fitted with an extended base plate to limit its capacity. When I got mine I switched out my 10 round mags base plate to the pinky extensions that came with the gun. I plate to get another 10 rounder and put the flat bottom base plate on it for reloads.