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  1. #1
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    Sig MCX Discussion

    I think Sully and I are the only ones with these things, but they're pretty sweet. I finally got to shoot mine a bunch, and it is smooth. Flipping the gas block over to suppressed mode keeps the rifle feeling almost identical when I throw my Saker on. A couple guys at the range today are very interested in the MCX for 3 gun, and it's easy to see why.

    Should we trust Sig? After the botched 556, I wouldn't. Heck, I think they are generating a lot of hate right now with the gen 2 MPX changes that aren't backwards compatible with the original guns. I'm surprised at how much I like the MCX, so hopefully Sig can get their act together and support it. All the proposed short barrels in several calibers, alternate handguards and stocks, and caliber conversions are still vaporware.

    Will - Owner of Arisaka LLC - http://www.arisakadefense.com

  2. #2
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    I thought you sold that thing.

  3. #3
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    He had a change of heart.. But I really want to test it out ASAP!

  4. #4
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    Quote Originally Posted by UWone77 View Post
    I thought you sold that thing.
    The buyer backed out, so I thought I'd at least try it out. Probably shouldn't have, because now I want to keep it. :)
    Will - Owner of Arisaka LLC - http://www.arisakadefense.com

  5. #5
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    Sig's recent record scares me, and the fact that they are already producing a gen2 doesn't give me great confidence. I do think it is a very interesting design and I think that the potential is huge. I will agree they are very smooth shooting.
    FFL 07/ NFA 02
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  6. #6
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    Will - Owner of Arisaka LLC - http://www.arisakadefense.com

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    If I lived somewhere I could SBR one I'd be more interested. The folding stock would make it a nice backpack gun.

  8. #8
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    Quote Originally Posted by wsaraceni View Post
    If I lived somewhere I could SBR one I'd be more interested. The folding stock would make it a nice backpack gun.
    I think the MCX is only a viable platform as a SBR. Full size I see no benefit.

  9. #9
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    Agreed. So I'll never get one unless I move out of NJ. But the weird thing for me is if rather have the McCain receivers over the 556. I just wish they could make
    It have the 556 classic forend and folding stock. Until then it's just another case of sig building ALMOST what i want.

  10. #10
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    Now that I have an MPX I'm looking more closely at the MCX. I'm impressed by the design although I'm generally a mil-spec DI guy. I didn't mind venturing further afield on the 9mm platform as I never seriously consider 9mm ARs anyway (would have gone with an MP5).

    I don't know any other company that is investing/risking as much in R&D for the civilian consumer as Sig and the innovation is showing. They've had some issues along the way (gen 1 / 2 w/ MPX), but I'd rather them continue to learn and risk obsoleting themselves then abandoning all development once it's out the door (which we've seen several times from other manufacturers).

    It will be a while until I have budget to seriously consider picking up an MCX, but I definitely understand the attraction now.

  11. #11
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    Sorry to dig this old post up, but I've had the MCX on my mind recently.

    Any further thoughts from folks on the MCX? Experiences with them over the last few years?

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    Name:  20200218_223301.jpg
Views: 736
Size:  1.57 MB

    Love my 11.5 virtus. Smooth as butter.

  13. #13
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    SPEAR LT

    Quote Originally Posted by BoilerUp View Post
    Now that I have an MPX I'm looking more closely at the MCX. I'm impressed by the design although I'm generally a mil-spec DI guy. I didn't mind venturing further afield on the 9mm platform as I never seriously consider 9mm ARs anyway (would have gone with an MP5).

    I don't know any other company that is investing/risking as much in R&D for the civilian consumer as Sig and the innovation is showing. They've had some issues along the way (gen 1 / 2 w/ MPX), but I'd rather them continue to learn and risk obsoleting themselves then abandoning all development once it's out the door (which we've seen several times from other manufacturers).

    It will be a while until I have budget to seriously consider picking up an MCX, but I definitely understand the attraction now.
    So, here we are 7 years later with the SPEAR LT, the 3rd generation of the MCX. The SPEAR LT addressed the main thing that was holding me back from the MCX: fully ambidextrous controls. So with the looming WA AWB I finally jumped in with the 11.5 5.56 pistol, immediately dropped my Form 1, and also purchased the 300 AAC conversion parts. While I do want to get one of Sig's new suppressors, I decided to run the SF RC2 for now. Sig lore hit home and I could NOT get the Muzzle Device off the barrel so sent the barrel back to Sig. They sent me a new barrel so apparently even they had a hard time removing the flash hider! I've added an EXPS3, Arisaka light set-up, KAC BUIS, and Surefire closed tine flash hider / SOCOM mount. Decided on the SL-M stock which is new for me. I'm usually a SOPMOD stock guy, but those are too wide to sit close to the receiver when folded. The SL-M seems like a good compromise. Also added the Tango Down vertical grip, which reminded me of why I hate the M-LOK system (yes, it looks better than Keymod, but actually using Keymod is much easier IMO). I'm also using Magpul M-LOK panels for the first time. I like them, but the geometry of the SPEAR LT handguard makes them not want to sit flush one the 3/6 o'clock sections once you get aft the cutout for the M-LOK sections at the 1:30 / 10:30 positions, so am using a narrower BCM panel section on the right side.



    I finally started running some drills with it yesterday to get a feel for it. Initial impressions are very positive. Super smooth and light recoil. I was hoping for this, as I believe the MPX is smoother than even MP5s, which are sweet, so my initial reaction is the SPEAR LT gives you roller-lock level smoothness in the M4 platform - which is awesome. The stock trigger on the SPEAR LT is also quite good. The Geissele Super Tricon is my go-to, so I generally prefer two-stage triggers. Sig's trigger is a two stage with similar pull weight to the SSA (4 to 5ish lbs, I'm guessing), is pretty smooth, breaks cleanly and has a good reset. While not as good as a Geissele, I don't feel the need to replace it. Sig has also improved the ambi charging handle at least over the stock version that came on my MPX that I eventually replaced with a Raptor, but I don't feel an urgent need to replace the CH on the SPEAR LT.

    Now for the bad news - I realized pretty quickly that my MD must not be concentric as accuracy when shooting suppressed was just horrible. No damage to the suppressor, thankfully, but I must have gotten a light baffle strike or nick as i had keyholes on paper. Luckily I figured this out after just a few rounds. The challenge here is Sig uses a taper at the end of the barrel instead of a 90 degree shoulder like everyone else in the world, so you end up needing a taper adapter if you want to use someone else's muzzle device. I used the Sig taper cap, but I'm sure it ended up not going on perfectly concentric. So, I need to re-install the MD and I'll use this as the excuse to finally get the bore alignment rod(s) that I should have always been using anyway. A little internet research quickly showed that I'm not the first one to have similar issues, so for those that make the jump over to the MCX just be aware and cautious when using any thing on the muzzle that isn't Sig's taper system.

    I know there are some concerns out there regarding the rigidity of the handguard, especially for the 16" versions, but I'm not currently concerned about that given my SBR setup.

    Overall, though, I think Sig has a real winner with the SPEAR LT and suspect this will end up becoming the first thing I reach for when heading to the range.

  14. #14
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    I received my SureFire suppressor alignment rod (also co-branded with Geissele) today and quickly confirmed my suspicions that the Sig Taper Cap was not mounted concentric and thus causing my Flash Hider / Suppressor Mount to not be concentric:



    However, with some trial and error I figured out a few tricks that allowed me to successfully mount the taper cap and Flash Hider to achieve a concentric Suppressor mount:



    If you are going to install your own suppressor mounts on any Sig with tapered barrel using a taper cap, I suggest that the $70 on the alignment rod is cheaper than damaging your suppressor. A few tips that may be useful to those following this journey:

    - Check alignment concentricity of MD + Suppressor without using the tap cap first. This should confirm there are no issues with the barrel threading and give you the confidence that if you have alignment issues with Taper Cap + Muzzle Device + Shims it is a factor of the installation, not the hardware
    - Next install the MD + Taper Cap with no shims. I put a little anti-seize on the barrel taper so I could spin the taper cap easily. Use the force from threading the MD on the barrel to seat the Taper Cap. That should help with concentricity. Torque per spec, check alignment.
    - If alignment is good and no timing is required, you're done, but if timing is required back off the MD and install shims. The Taper Cap should stay put pretty well from torqueing the MD previously. I'd avoid putting the paper thin shims directly against the taper cap as I destroyed one when it was compressed against the taper cap. Try to keep a thicker shim against the taper cap. Keep checking for alignment. If you lose the alignment, knock off the taper cap and start over.
    - Note that removing the taper cap after it's received torque can be challenging. I used an adjustable wrench around the barrel and backed up against the taper cap and hit the wrench with a light hammer to knock off the taper cap.
    - It was basically trial and error until everything aligned properly under torque

  15. #15
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    Thanks for posting this. I ordered the 7.62 version. I've had "issues" with a 300BO upper, and my son's 308.
    NRA Benefactor Member
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