I'm sure this topic has been discussed alot, but I can't stay focused while doing searches (I get side tracked looking at other topics).
Do other Steyr model magazines fit the S-40? Did I read somewhere that a M-40 12 rnd mag will fit my S-40?
It should fit just fine. I think a lot of the S owners use a regular S40 magazine in their pistol for carry, but carry a M40 mag as a spare. If you really want to cram a lot of rounds in there, you can do the "Wulf Sigma conversion" to put 15 rounds on tap. 8)