So I’ve searched this and know it’s been talked about, but every time I click a post it takes me back to the home page, so here it is again (sorry). Snagged myself an MPX-K for my birthday on Sunday (DOM:10-22-2020) to replace my stribog SP9A3, which I had no issues with ever. I took it to the range in a huge hurry today to just get a quick zero on it, and I couldn’t do better than 3-4 inches at 25m supported. I’m not expecting sub MOA accuracy, but I can shoot nearly that kind of group with my P-07 standing if I take my time. I lubed it, checked torque on the barrel, optic, etc.. and everything looked good. I had/have really high hopes for this platform, but is this the kind of accuracy I’m going to just have to live with, or is there some kind of issue going on possibly? I’ve got 25m from my bedroom to my front door, and as of now I’d be hesitant to use this as an HD/SD platform. This was with the factory birdcage, and today threw a tapered tri-lug adapter from In Lead We Trust on there, so will try it and report back. When I called Sig they said something must not be torqued properly, and that offhand, 3-4” is ‘standard’ at 25m, but should be significantly tighter when supported. Pics for your time Attached File
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Sig MPX barrels have something wrong with them imo.  You can't put a damn tri lug on them without them becoming wildly inaccurate.

I bought the in led we trust barrel with the integrates teilug and it's been grate.  Pisses me off that Sig did such a bad job with the MPX barrel and charge so much money for it.

So I bought Rob’s (ILWT) tapered tri lug to try and remedy the problem. If that doesn’t work, I may sell my 4.5” barrel with 30 rounds through it for like $200 and buy an ILWT barrel. That brings me to my next issue. I can’t get the barrel out lol. I have undone the screws, used my torch to try and separate it, and nothing. This has been a grail gun of mine so I’m willing to put up with some shit, but other than the look and the quality of the build, I’m less than impressed thus far.

Hope you get it worked out. My experience with Sig (and their CS) has been terrible. Maybe they’ve improved some, sounds like they’re “trying” to be helpful at least.

Well, I hope so. They’re being nice, but I don’t think the lady I spoke with knew what she was talking about. I told her I had my optic torqued to 25in/lb, and the barrel to 40in/lb. She must have just been reading right out of something cause she said ‘I think the problem could be that the manual says the optic should be at 28 inch per pounds, and the barrel should be at 30 inch per pounds, or something called t25’

I've had the opposite experience. My Gen 1 factory 4.5" barrel with tri-lug adapter (can't remember the maker) is much more accurate than my Gen 1 machined tri-lug/threaded ILWT barrel which now just sits in the parts pile.

I’m actually hoping to get to the range with it here in the next hour or so and see if the tri lug with taper has helped at all

Just a quick update after a gunsmith look over, a trilug install, concentricity check, both with and without a can. Attached File
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Got any other ammo besides Blazer to try?

Yeah man I tried blazer, Sig 147gr hollows, flat nose subs, round nose subs, 114,124, 140,147 and 150gr. All the same groups. It’s just not accurate. I’m absolutely blown away by the handling and the overall construction of the gun. I really want to love it. I’d rather like white dog shit with Dale Dobeck in the park than say I’m pleased or even will accept the accuracy I’m getting from it

My Gen2 MPX is the same way with a suppressor.  It shoots fine with factory 4.5" barrel and birdcage.  With the tri-lug adapter alone the groups open up a little bit.

With the suppressor groups are 6-8" at 25yds. I even tried two different IWLT 4.5" barrels with the same results (Rob sent me a replacement).  

I have thought about trying IWLT 6.5" to see if it has any better results.  The only other thing I haven't tried is the adjustable gas block.  I am pretty frustrated with my MPX and have been looking at APC9s recently.

Sorry you have a bad one. My MPX K is more accurate than the MP5s I owned. Just a tack driver. If you feel you have issues with it, send it to Sig to check out. I love my MPX. Best 9mm PCC out there.

I would send it back to Sig.Mine are gnats ass accurate.I’ve got 2 of the current model with the flat trigger and m-lok rail.I’ve got no plans to suppress mine.A large part of the problems I’ve ever seen personally or heard about center around people trying to suppress them.There are so many variables with suppressor design and construction that it’s gotta be hard to design a gun that will work good with all the suppressor and ammo combos double extra for a small caliber gun that’s actually gas operated.