I searched, but could only find one thread on this, from 2008 or so. That post mentioned "14+1" magazines for .40 S&W/.357 SIG. I've seen numerous mentions of 12-round, 13-round, and 15-round Mec-Gar mags, and I have six 12's and two 15's. I think four of the 12's came with my P226 DAK when I bought it, and I got a couple more with the "Anti-Friction Coating" afterward. I only acquired the 15's in the last month or so, and they were big buck$.
The lowest witness hole on my flush-fit ones says 12, but are they really 13-rounders? I haven't tried loading one past 12, and I s'pose it could be a dumb idea to try that. The Mec-Gar site lists Model MGP2264013, which says "Increased capacity to 13-rounds while remaining flush-fit." In the photo on the site, it looks to have a different base from the ones I have already.
The other type is the MGP2264015, which adds a "Plus-2 Adapter" (also available separately, if you can get any) to the basic mag. The bottom witness hole on the ones I have says 13. They're about 5/8" longer than the other type. <http://www.mec-gar.com/Magazines/Sig-Sauer/MGP2264015
Are there actually two different kinds of flush-fit .40/.357 mags for the P226?
Thanks for any clue-ins.