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Thread: Sig MPX and MCX Full Autos

  1. #1
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    Sig MPX and MCX Full Autos

    Hello ALL
    anyone have experience with any of these Firearms?
    They are Post 86 of course and there are some that have been converted
    There are a couple of firms that do the conversions.
    Thanks
    Haris1
    Any One Who Thinks The Pen is Mightier Than The Sword
    Obviously Never Encountered Automatic Weapons
    General Douglas MacArthur

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    I had a full auto MPX...used a post sample DIAS and PMM trip. I hated it. Gassy and LOUD suppressed. Over 1100 RPM and no way to tune it. I also had the 4 position ILWT gas regulator as well as their 3 lug barrel. So glad I sold the host gun and didn't commit to drilling an auto sear pin hole.

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    While we do not have either, I have shot both the factory MPX and Scorpion.........both suck
    Chris Hipes
    Hipes Consulting Services LLC
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    Registered User rentprop1's Avatar
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    I have one, was in love with the MPX forever, used to see that thing in the gun mags and drool.....committed and took the plunge when they first came out, wanted to have one of the 1st guns, drilled the hole for the auto sear, made my own Z-bar to trip the paddle, its a Gen 1 gun, Kak tube and Strike AR stock, cut the barrel back to 4.5 inches and run a Omega 9K on it full time under the full length hand guards, I shot it 2 years in a row at Knob Creek, its fast, like FA Glock fast, haven't fount someone with a RPM shot timer to ever figure out the true RPM.

    I have a Scorpion Evo as well, also super fun, only the trip is registered so I didn't burn the host, don't know why Chilli says they suck, totally fun guns, lots of folks pay to use them as rentals, while not classics as Uzi's, M11's or Stens #eyeroll they sure trun heads and run like raped apes.

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    I too was crazy about the MPX before it came out. Got a Gen1, but didn't want to drill the hole so made my own trip that worked but wasn't heat treated and later bought the PMM one.
    At that time MPX specific triggers were not available and so I tried using my Geissele SSF as well as standard M16 firecontrol. I was getting horrendous trigger slap and didn't use the Geissele SSF much as I was afraid I was going to break it. I think it was around that time that Geissele warned that use of their triggers in an MPX would void the warranty due to the fast cycling bolt.

    So I put some M16 firecontrol parts in mine instead of the Geissele. Then tried what I could to slow it down with the ILWT 4 position gas regulator which didn't do much.

    I think all full autos are fun but it is all relative.

    Not to speak for Chili but I like my full auto's to run around the 600 RPM range. The exception to that is 22LR. Whatever it will run reliably at will do for 22.
    For open bolt, there are many choices that run in the 600 RPM range and if you want faster, you can easily tune most of them to run at the rate you want which is great.

    Now in the closed bolt world, getting something to run in the 600's SMOOTHLY is hard. Yes, I've had straight blow back 9mm Colt's run as slow as 465 RPM but they bounced all over the place.

    One of my C2 friends has won Knob Creek several times and has just about every post sample SMG you can think of including BT's, Scorpions, MPX's, etc....As he is always trying to rival the MP5. He doesn't like the MPX or Scorpion either for the same reason I don't, too fast and nothing you can do about it.
    He said if he is in a match that forces you to keep the selector on full, his choice for a closed bolt is still the MP5 but again still waiting on something better....MP5 still cycles a tad too fast to easily pull singles.

    These days, I just compete at the Port Malabar match in FL in a relaxed environment. Not many full auto guys like there were 10+ yrs ago. So we don't do like the Creek and have open vs closed bolt classes. However, I still run with the selector on full on whatever I'm running and like to be able to pull singles, doubles and triples on demand. Something I can't do above 800 RPM reliably. Never crossed my mind to use the MPX in one of these matches.

    Until something better comes along, I'll continue to run my tuned CMMG RDB that I have running in the 600's smoothly. If I want to go faster, I can easily swap bolts which control the delay, springs and buffers to go over 1K RPM. All using my Geissele SSF that I'm not concerned about breaking as the recoil impulse is softer than a 556.

    Several are so excited to shoot the MPX since they are seen in movies and video games but after trying it compared to my tuned CMMG RDB or MP5 or even UZI's, they don't care for it. Especially when trying to engage several targets at such a high cyclic rate.
    With the piston design, I think it is one of the worst suppressor platforms. So much port pop which is LOUD and gassy. Several friends wouldn't even complete a mag and hand the gun back saying it sucks from the blowback.
    I do have a friend that got his full auto MPX integrally suppressed and from what I hear that is the way to go but since I can't control the cyclic rate and I decided not going to invest more into the platform and get rid of it.

    Picture below of my MPX when I clocked mine.

    Last edited by amphibian; 12-24-2021 at 11:22 AM.

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    Maybe "suck" was to harsh They both were just to fast and bouncy compared to most things I shoot. Best closed bolts that I have shot in 9mm, CMMG RDB, MP5, AUG. None are as smooth as a good open bolt IMHO though.
    Chris Hipes
    Hipes Consulting Services LLC
    FFL/SOT 07/02
    poulan10takethisoutsoidonotgetmorespam@yahoo.com
    North Texas

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    I think I remember someone running one at creek 2 or so years ago. I remember them saying it wasn't great and finding it hard to believe. I mean. I guess it's like the Kriss Vector; who has actually shot one in FA in real life?
    Last edited by Gaujo; 12-25-2021 at 10:41 PM.
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    Kriss Vector also has a ridiculous cyclic rate -1200 RPM. I'm personally not interested in any 9mm running over 700RPM for a SMG match.

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    Converted or repaired close to 100 of both that people thought they knew how to do. Both of the guns are hard on parts by design. The MPX will break hammer pins because the unlock time is just that violent. Same reason they had to put a bridge in it. Overall a decent blaster though. The early gen 2 guns are the one to convert if you can find them. They came with an undersized gas port compared to the Gen 1's.

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    Registered User jurist's Avatar
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    The Kriss Vector sucks in real life. They constantly break hard to replace parts in full auto. As far as the MPX the current MPXks have TERRIBLE trigger slap in full auto.

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    Quote Originally Posted by jurist View Post
    The Kriss Vector sucks in real life. They constantly break hard to replace parts in full auto. As far as the MPX the current MPXks have TERRIBLE trigger slap in full auto.
    If your MPX has trigger slap it was built wrong by whoever did the conversion.

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