I have 2 of each - the 2 P99c mags that came with my gun, and 2 SW99c mags I ordered from cdnn. I recently noticed that with mine, at least, there is at least one difference that I haven't seen documented here before:
The SW99 mags have different springs in them than the P99c mags. They have 2 less coils, resulting in a less powerful spring. (They appear to be made from the same type of coiled wire.) The reason I noticed this was that I had long noticed that they didn't eject as positively as the P99c mags, which practically fly out of the gun when the mag release is depressed, and they're slightly easier to load. This prompted me to disassemble them side by side, and lo and behold, the springs are different. I'm not sure if it's anything to be concerned about, as both types function properly, but I figured it might be of interest to some people. It certainly seemed goofy to me, anyway.
If there's significant interest, I can post some comparison shots, though it's just a pair of springs, so it's probably not too exciting to look at.
The SW99 mags have different springs in them than the P99c mags. They have 2 less coils, resulting in a less powerful spring. (They appear to be made from the same type of coiled wire.) The reason I noticed this was that I had long noticed that they didn't eject as positively as the P99c mags, which practically fly out of the gun when the mag release is depressed, and they're slightly easier to load. This prompted me to disassemble them side by side, and lo and behold, the springs are different. I'm not sure if it's anything to be concerned about, as both types function properly, but I figured it might be of interest to some people. It certainly seemed goofy to me, anyway.
If there's significant interest, I can post some comparison shots, though it's just a pair of springs, so it's probably not too exciting to look at.