I have several P239s at the moment. All are chambered for the 357SIG cartridge.
I have been shooting 357SIG since I was first introduced to 357SIG out in Texas when DPS was evaluating it as a duty cartridge, that was back in the early 90s. I have been carrying and shooting P239s since the mid 90s
While DPS initially adopted the P226 as the uniform pistol, the P239 was added for plain clothes or whomever could justify the smaller sidearm sometime in the early 2000s. The P239 with the 405- inventory number on it that is pictured above is my DPS pistol
While the original 357SIG/40S&W mags hold 7, the agency contracted with SIG for an 8 round variation using a +1 base plate. These were not polished blue like commercial magazines, they were phosphate coated for the improved corrosion resistance. We got them sealed in little baggies in a big old box.
I traded all my 7 rounders in for the 8s when that happened. The extra extension barely changed the mag length
I find the P239/357SIG to be a fantastic platform. The pistols are accurate and powerful, not to mention small enough to conceal. The Hard Chromed P239 pictured above was done by Accurate Plating and Weaponry and it is the pistol that I was carrying tonight
These were used by many agencies including the Secret Service
The P225 and P239 are distinctly different firearms. Neither evolved from the other. The reintroduction of the P225-1 is a design that is closer to the P239 than the original P225.
The 9MM magazine of the P225-1 is the P239 9MM magazine with a different base plate on it
Spare parts and extra magazines are always available, just not from the Factory. No different than looking for a Model 19 barrel from the 70s. They are out there to find.