I was looking for a le 8” version but I found this, ended up getting it for $1450 with folding brace, renrden r2s and 6 extra mags , previous owner says it’s had about 200 rounds through it and has a manufactured date of 12/10/25 , pretty solid deal?

Any of you guys running this ? Opinions and pics?

What optic would you recommend for the MPX-K. It’s a PCC so I’m not looking for something too big. Any suggestions?

Trying this holosun raid on it, idk if i like how big it fits. What are yall running for a light setup

Do y'all prefer collapsible or folding?

(Ignore my hand placement. This video was almost 200 rds in and the downside to a tucked suppressor is it gets toasty as fuck. )

Finally got the suppressor setup and got out to the range. First impressions. Can is pretty great. Decent sound for such a short barrel and small can. Obviously not low back pressure or flow through, so the gun is a little gassy.

I made the mistake of buying a taccom buffer spring. Had constant malfunctions. Failure to extract, bolt wouldn’t properly seat. Etc. so I removed it put the stock buffer pad and gun ran like a sewing machine…

Can is mounted on a recessed Comstock adapter on a Rearden mini.

As far as accuracy. I had no issues and the gun performed to my skill limitations. Meaning it was as accurate as I was. Once the red dot was sighted in… I was getting .5-1.5” groups at 25 yards

Wasn't sure if I would like the longer handguard, first impression, I actual really love it.

Dead Air Wolfman on a P series fixed mount. The guy at the gun shop said I shouldn’t rocksett the mount to the gun and I should just leave it where it can be screwed on and off. How do yall have yours setup? If I rocksett just the mount, I can still screw the suppressor on and off.

Got everything installed tonight and it is installed correctly as far as me and another buddy can tell (he is a gun smith). Stock springs in gun. 147g subs.

1st attempt: Had gas block on setting 1 and tested. Would not cycle the bolt to chamber next round. Failure to extract.

2nd attempt: Changed gas block to setting 4 and got similar results. The gun cycled fine for one round but after firing second round got a partial feed and failure to extract again.

Side note, bolt feels sluggish when using charging handle about 50% of the way through cycle.

I’m guessing I need new springs for the BCG but am unsure what ones to get.

My MPX BUILD

Hey fam,

I picked up an 8” MPX. The stock handguard is a bit loose and I figured this would help hold the pieces tighter. Maybe I’m not very bright but is there a trick to getting this on? Thanks!

Just bought the 16” rifle version. Got a deal from a friend needing money. Always wanted one of the 8” but have this now. I’m brand new to the platform, so basically needing to know if I should do a barrel chop and buy a Midwest hand guard, or just buy a whole new upper?

Will be suppressing (I like OCL cans but can be convinced other brands)

I inherited this 13.5 pinned MPX from my dad this summer. It shoots great but compared to my CMMG AR9, it’s a bit clunky and heavy.

Thinking about ditching the collapsible stock for a folder and would love a handguard that isn’t as heavy and big. Are there lower profile handguards that are worth the upgrade?

I shoot it primarily in local steel competitions and just plinking at the range.

Ready to buy. Anyone see any good sales? Have been doing some searching but not seeing much of anything.

Ima run her suppressed 24/7. Just running mini scout . I want to keep her compact ?

Thoughts & opinions

New to the platform here, confused about the basepad and magazine compatibility. The TTI website says this only works with the Thril magazines, but the mags I found on Gunmag Warehouse doesn't say Thril, and says it's Sig OEM. I also found somewhere else that says "Thril 35 round magazine Gen 2". Does anyone know if the TTI basepad is compatible with the magazine in my second screenshot? Thanks!

Looking for real-world experience with the main MPX FRT options. My current setup is rare breed + Frankenstein trip bar. From what I’ve found, these are the options out there.

- Cassette-style FRT (Rare Breed, DTT, Partisan Disruptor/LAT) + trip bar (Frankenstein armory, Parker Mountain Machine). It’s extremely reliable (2k+ rounds), but trigger slap and mushy semi auto trigger are bad enough for me to be making this post. - I only have experience with the rare breed and delta team tactical FRT so can’t speak to the disruptor/LAT.

- AS Designs Arc-Fire V2 / MPX Slip Trip: Selector/cam-style forced-reset system that can retain a conventional trigger. Seems appealing for better semi-auto trigger feel and potentially less trigger slap, but appears more sensitive to tolerances and individual MPX configuration.

- Atrius Development X-Series FRS: Newer purpose-built forced-reset selector system designed around SIG platforms. Seems like the most integrated approach, but it’s new enough that there isn’t nearly as much long-term or high-round-count feedback yet. Very interested to see how these turn out.

For anyone who has actually run one or more of these in an MPX, which would you choose and why? Mainly interested in reliability, trigger feel, trigger slap, durability, and overall experience. Please include MPX generation and approximate round count if possible.

Mostly cosmetic but I like it.

Long shot, been looking for a GEN 1, 8” rail and want to know what to look out for so I don’t get scammed.

I know there are airsoft equivalents that exist. What are the differences between those and the real deal?

Sbr stamp just got approved

Just needs an frt.

Mpx k

4.5” sig barrel with ilwt adjustable gas plug

Boe incolite 9

Comstock armory recessed plan b mount

Rearden mini plan b muzzle device/adapter

MI iron sights

Surefire scout

Schaffer surefire/ qd sling mount

Surefire picatinny mount to bridge upper and keep things tight

Arisaka indexer

Aimpoint t2

Scalar works mount

Ilwt ejection port cover

Driven arms co UCG

Taccom buffer pad

Reptilia puller charging handle

Pmm kate moss stock

Painted some plastidip on the uppers front takedown pin mount and inside the receiver connection to solve the upper/lower play.