Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Suppressor Zero Shift Fix?

  1. #1
    Site Supporter
    Join Date
    Feb 2011
    Location
    North Carolina

    Suppressor Zero Shift Fix?

    Can anything be done to fix extreme zero shift due to mounting a suppressor?

    I have a Gemtech GM9 that, when mounted via 3-lug to a Sig MPX, will, at 50 yards, group over a foot to the left compared to when the suppressor is not mounted. (Curiously, at 25 yards, the leftward shift is only about 2-3 inches or so.)

    By comparison, when the same suppressor is mounted via 3-lug to a Colt 9mm carbine, there is almost no discernible shift at 50 yards.

    Any ideas on the cause, and how I might fix such an extreme shift on the MPX?


    Sent from my iPhone using Tapatalk Pro

  2. #2
    Site Supporter
    Join Date
    Aug 2011
    Location
    TEXAS !
    Quote Originally Posted by nalesq View Post
    Can anything be done to fix extreme zero shift due to mounting a suppressor?

    I have a Gemtech GM9 that, when mounted via 3-lug to a Sig MPX, will, at 50 yards, group over a foot to the left compared to when the suppressor is not mounted. (Curiously, at 25 yards, the leftward shift is only about 2-3 inches or so.)

    By comparison, when the same suppressor is mounted via 3-lug to a Colt 9mm carbine, there is almost no discernible shift at 50 yards.

    Any ideas on the cause, and how I might fix such an extreme shift on the MPX?


    Sent from my iPhone using Tapatalk Pro
    Itís not the suppressor. Itís either a defective barrel because the threads are not concentric or itís the tapered shoulder on the MPX barrel.

    Are you using an adaptor to square the shoulder and mount the 3 lug ? SIG used to sell these but stopped and wonít say why.

    Options are:

    send it back to SIG

    Buy an aftermarket barrel

    Buy a SIG or Q suppressor with a matching taper

    MAC had a similar experience here:

    Last edited by HCM; 08-28-2020 at 12:41 AM.

  3. #3
    Site Supporter
    Join Date
    Feb 2011
    Location
    North Carolina
    Quote Originally Posted by HCM View Post
    Itís not the suppressor. Itís either a defective barrel because the threads are not concentric or itís the tapered shoulder on the MPX barrel.

    Are you using an adaptor to square the shoulder and mount the 3 lug ? SIG used to sell these but stopped and wonít say why.

    Options are:

    send it back to SIG

    Buy an aftermarket barrel

    Buy a SIG or Q suppressor with a matching taper

    MAC had a similar experience here:

    Thanks for your insights! I do remember being surprised at the tapered barrel when I removed the original flash suppressor, and wondering if it would cause any issues with interfacing the 3 lug muzzle device. I guess the answer is Ďyes!í

    I wonder if using this 3 lug adapter supposedly specifically designed to interface with the tapered barrel might also fix the issue?:

    https://inleadwetrust.com/product/hk...essor-adapter/



    Sent from my iPhone using Tapatalk Pro

  4. #4
    Site Supporter
    Join Date
    Aug 2011
    Location
    TEXAS !
    Quote Originally Posted by nalesq View Post
    Thanks for your insights! I do remember being surprised at the tapered barrel when I removed the original flash suppressor, and wondering if it would cause any issues with interfacing the 3 lug muzzle device. I guess the answer is Ďyes!í

    I wonder if using this 3 lug adapter supposedly specifically designed to interface with the tapered barrel might also fix the issue?:

    https://inleadwetrust.com/product/hk...essor-adapter/



    Sent from my iPhone using Tapatalk Pro
    Maybe, if the issue is the taper. However itís more likely it is a defective barrel with non concentric threads.

  5. #5
    Site Supporter
    Join Date
    Feb 2011
    Location
    North Carolina
    Quote Originally Posted by HCM View Post
    Maybe, if the issue is the taper. However itís more likely it is a defective barrel with non concentric threads.
    Besides the extreme zero shift, is there any other way to tell whether the threads are truly concentric or not?



    Sent from my iPhone using Tapatalk Pro

  6. #6
    Quote Originally Posted by nalesq View Post
    Besides the extreme zero shift, is there any other way to tell whether the threads are truly concentric or not?
    There are alignment rods out there you can use to check for concentricity once the can is mounted, though some of them aren't cheap (e.g., https://www.brownells.com/gunsmith-t...rod104864.aspx). You might be able to tell with just a visual inspection. Might.

  7. #7
    Site Supporter Sensei's Avatar
    Join Date
    Jul 2013
    Location
    MI/NC
    Quote Originally Posted by HCM View Post
    Maybe, if the issue is the taper. However itís more likely it is a defective barrel with non concentric threads.
    Yep. It sounds like Sig had a bad batch of barrels with non-concentric threads. Good luck getting them to admit it.
    I like my rifles like my women - short, light, fast, brown, and suppressed.

  8. #8
    Quote Originally Posted by Default.mp3 View Post
    There are alignment rods out there you can use to check for concentricity once the can is mounted, though some of them aren't cheap (e.g., https://www.brownells.com/gunsmith-t...rod104864.aspx). You might be able to tell with just a visual inspection. Might.
    This is a cheaper alternative that was posed over on M4C by JPMuscle. I havenít picked up a can yet, so I havenít tried them.

    Name:  D1BD780D-B683-473C-B76A-CA1BF0C3A071.jpeg
Views: 191
Size:  92.4 KB

    https://www.mcmaster.com/8893K191-88645K33/

  9. #9
    King of Craft Clusterfrack's Avatar
    Join Date
    Jun 2013
    Location
    Redneck wonderland

    Suppressor Zero Shift Fix?

    @nalesq, thatís a pretty big shift. Are you getting baffle strikes? Key-holing?
    "BJJ is sort of like nonconsensual yoga"
    "You donít really graduate from certain problems or certain thingsÖ like you always have to work on trigger control and pulling the trigger straight. " --Ben Stoeger 1/24/2018

  10. #10
    Quote Originally Posted by omega9 View Post
    This is a cheaper alternative that was posed over on M4C by JPMuscle. I havenít picked up a can yet, so I havenít tried them.

    Name:  D1BD780D-B683-473C-B76A-CA1BF0C3A071.jpeg
Views: 191
Size:  92.4 KB

    https://www.mcmaster.com/8893K191-88645K33/
    I've bought a fair amount of drill rod over the years. It isn't spec'd for straightness. In general, the stuff I've gotten won't be straight enough to use as an alignment rod.

    Maybe shorter, fatter pieces for a pistol, but in general I don't think it will work well for rifles.

    I have one of the .30 alignment rods, and I had the same idea, and tried several pieces of drill rod (and other stock) I had laying around as rods for a 22, and none were straight enough to be useful. You might get lucky, but don't count on it.

    Any machinists in the house? It's fairly easy to grind long skinny stuff to an accurate diameter with a centerless grinder. I don't know how you grind it straight.

User Tag List

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •