I have three hi-cap SW99 mags and four hi-cap P99 mags. I have used both in my P99 with no problems. They appear identical, except that they floorplates say "S&W" or "Walther" depending on the mag.
I bought the SW99 mags when the ban first lifted, because they were what I could get at that price. Now the Walther mags are around, so I'm getting those just because I like the banner (hey, it's a good enough reason).
Thanks for getting specific that's exactly what I needed. The plan is to get the SW99 compact as a back up (BUG), to compliment my P99AS. I intend to carry only one spare mag (the P99 15 rounder) so the theory is if the P99 goes down, or I loose it somehow, i can use what's in the Smith then if I need it slap the P99 mag in the SW99C (overhang bedamned) and extracate myself from whatever situation i should not have put myself in in the first place. So brass tax, I should be able to put a P99 mag in a SW99C. You would think they would know this, you think they have any interest in UP-Selling me?
It was on the faqs though I have not used a normal p99 mag in my p99c since they both the p99 and p99c sw99 and sw99c are in detail the same guns there is no reason they would not work give it a try. If you plan on having both any way.
eeni: I got the same response you did when I called both WaltherAmerica and S&W (really same place). I spoke with two different people a few days apart from each other, and they both told me that the mags would work, but not as well as if you kept the Walther mags in the P99 and the S&W mags in the SW99.
They said they could not guarantee 100% reliable feeding if you mixed the mags. I called soon after the ban had lifted.
I don't know why they would say this... maybe the sales force isn't trained well enough to know how similar these two handguns are.
To be fair, I have spoken to a few people there who truly knew their way around the P99 and could sense their appreciation for handguns.
I never pursued it further since I was able to find 16 round Walther magazines.