So I've got a MPX on the way. Should be at the local shop in a few days. It's a 8" Gen 2. I've got the SB Tac Sliding brace as well.

Other than buy some 9mm and mags. Any other upgrades or things to look out for?

Congrats. Mine is a 8" Gen2 w/ the folding brace. I put a Radian charging handle in mine to prevent the finish gouging caused by the factory handle. I bought Gen1 mags from Gunmagwarehouse. Some guys have said Gen1 mags haven't worked for them but I haven't had any issues. I put a Vortex Strikefire2 w/ the cantilever mount and it's perfect for me. Backup sights co-witness well. I installed a small Sig laser on the left side of the rail, I modified (shortened) the keymod mount so I could mount it farther forward, this gave me enough hand room on the rail for a comfortable grip. Overall very happy with mine.

Don’t fully load the mags until broken in. Only aftermarket trigger I know of is Timney, Geiesele is still working on one. I dropped the folding stock for the SBR Tactical brace which is very nice. Fun little chunk of steel.

Wilson and Elftman also have triggers that they say work for the MPX, but Timeny is what I have in mine. All are drop in triggers.

Word is that Geissele has abandoned work on their MPX trigger.

Try not to giggle too loudly when playing with it at the range. Apparently some folks find that annoying.

Buy spare parts now for when SIG discontinues it in a few years. Seriously, who thought the 556 would be gone so soon.

Heck you can't even get them now.

On the note of spare parts, what would be good to have for this? May buy some while they still exist?

quote:

Originally posted by Fullsize.45:
On the note of spare parts, what would be good to have for this? May buy some while they still exist?

Wondering this as well.

Ideally, I'd like to have a spare bolt and buffer springs, but after some discussions with Sig, you can get firing pin, but they won't sell the bolt, or at least they wouldn't sell ME the bolt.

The firing pin is the only thing I've read of any failures about, after that the buffer springs would be nice to have.

Trigger springs are AR parts so not much worry there, and anything else past that would be a big enough issue you'd probably be sending the gun back to Sig.

quote:

Originally posted by BB61:
Buy spare parts now for when SIG discontinues it in a few years. Seriously, who thought the 556 would be gone so soon.

What exactly happened with that?

I'll admit I haven't paid attention to the rifle market for the past 2-3 years. So when I recently decided to look for a new one, no 556, or any 55X rifles to see.

sig discontinued new 556 production (which in and of itself wouldn't bother me), but at the same time essentially all support and parts for the installed base went with it. I have a gun with a lifetime warranty that sig simply does not have the parts to fix and can't.
Need a spring for your 556. good luck. Its a travesty full stop and they deserve to be abused about it.