I have one of these, the ones with the really neat camo finish, and understand that they have been discontinued. My question or questions revolve around the overlap between my pistol and the 10mm Legion, specifically in terms of parts replacement. How much do they share parts-like, the recoil spring? Should I try and stock up on any replacement parts that won't be around for the Legion?

Yes, you should have a few parts on hand like springs and pins. I’m pretty sure the internal parts are the same as the Legion. Someone who owns a Legion can chime in on this.

A spare extractor would be good to have, as well. Enjoy your new SIG.

I believe the internals are the same. For example, the Legion 10mm SAO lacks the SAO-specific SRT safety lever that is included with the 226 & 220 (45) SAO Legions - ie it lacks the short reset.

Welcome to the forum and congrats on your 10mm Hunter ownership. Yes it's always a savvy thing to load up on spare parts. As 2Adefender has already pointed out, a healthy supply of springs and pins would be at the top of my list of the parts to build backstock on. I'd also scarf up as many magazines as I can afford...and use, just in case production evaporates into nothingness in the near future. Which with how the winds blow in Newington, is always a very real possibility given SIG's past tendencies with "retirements". Just ask owners of the recently nixed P225-A/A1 about the lurch they've been left in.

In addition to the above consumables, I would pick up at least one extractor, spare followers, perhaps an ejector, and probably at least an extra proper 10mm SAO locking insert (particularly if you have the tendency to shoot a lot of ultra toasty 10mm loads). You can probably hold off on other internal components, but I admit that I can go (and have gone) overboard, especially with guns that I have a habit of shooting a lot. Hell I even buy extra barrels from time to time, and if I happen to come across a slide at a great price...