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Ruger PC Carbine and 9MM Suppressor Issues

Thread in 'Class III & NFA Discussion' started by js415, Nov 18, 2018.

  1. js415

    js415 ODT Junkie! Supporter

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    I recently bought a Ruger PC Carbine (9mm) and have not even fired it until today.

    Using the iron sights, laying the rifle in a rest, and shooting in my backyard I was able to get several 3 shot groups all within an inch or so. All shot within a inch of my bullseye on the target. I'm just looking to get on paper to mount a Holosun Red dot so I was pretty happy.

    I'm shooting in my backyard, so I was shooting at only 20yds.

    I'm not the best rifle shot so I was pretty happy with that.

    I mounted the Holosun and was able to duplicate the same groups, so I thought I was ready to go.

    Since it's threaded, I thought I should go ahead and give it a try using my Huntertown Arms Suppressor.

    I was able to duplicate the same groups, however, my point of impact shifted to the right a good 8-9 inches. No matter what I tried, the shots were all to the right. A long ways to the right!

    The same suppressor on my SBR shoots dead perfect using a similar Holosun, also in 9mm.

    Anybody have a guess or venture a guess as to a solution to this issue? Am I just going to have to not shoot the Ruger suppressed?

    Thanks,

    Jerry
     
  2. HydroAuto

    HydroAuto Frontiersman

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    Did you inspect your suppressor for any sign of baffle/end cap strikes? I'd assume that a factory could thread a barrel properly concentric/straight for a suppressor, but there are no guarantees. It might be marginally "good enough" for a muzzle brake or flash hider, but just enough out of spec that it is disturbing the bullets flight path as it goes through the suppressor.
     
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  3. GAgunLAWbooklet

    GAgunLAWbooklet The Hen that laid the Golden Legos

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    I've noticed a point-of-impact shift on my .22 rifle when I attach my AAC "Pilot" suppressor.
    That much weight on the end of a 22" and slender barrel can have a big effect on barrel harmonics--the whipsaw effect that you can't see, but is there nonetheless.
    Sometimes adding weight to a muzzle can dampen the whipsaw effect, or cause the timing to work to your advantage-- the bullet leaves the muzzle at the moment when the barrel has paused at the full end of its range of motion, prior to it flexing back toward the center or "straight line" alignment. It's actually better if the bullet leaves the bore when the barrel is paused and tilted to one side, rather than when the bore is moving through the dead-center alignment point.

    Try adding some weight to your suppressor, a few grams at a time, and test-shooting in between, to see if you can re-establish a spot of barrel harmonics that work for your particular ammo in that gun.
     
  4. js415

    js415 ODT Junkie! Supporter

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    I just took the endcap off since you suggested it. There are a very few, very light marks on the inside of the endcap. Just enough that you could see metal under the fouling, and barely enough that you could feel it with your fingernail.

    I suppose that could be enough to cause the groupings to go so far off. I'm not sure if they were there before today or not.

    Thanks for the suggestion,

    Jerry
     
  5. HydroAuto

    HydroAuto Frontiersman

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    Yeah, any touching is bad touching. Might want to ping one of the gunsmiths in the area to see what your options are for getting barrel threads checked, and trued up, if necessary. Or maybe re-boring the end cap a few thousandths to get enough clearance for no interference. (the latter would be a "git 'er done" solution, but less work than the former)
     
  6. spencer60

    spencer60 The Hen that laid the Golden Legos Supporter

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    I've used my Octane on my PC Carbine with no problem. It does shift it a little, but maybe an inch low at 25 yards. Nothing really significant.

    Since it's a take down you should be able to pop the barrel off and use a light to see if the threads are concentric with the bore.

    one other thing... If it's not direct thread, have you removed the piston assembly so it won't move around under recoil?
     
  7. Rolling_trip

    Rolling_trip The Hen that laid the Golden Legos

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    Same with my obsidian on my PC.
     
  8. jeep78

    jeep78 The Hen that laid the Golden Legos Supporter

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    Send a note to @Nonliberal , see if he can fix it or tell you who can.
     
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  9. Nonliberal

    Nonliberal Lead Janitor at Dobbs Defense Supporter

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    99% of the time it’s no thread relief in front of the shoulder. The other 1% of the time the shoulder is bad on the can. Pretty much always a mating issue. Easy enough to fix either way though.
    Even if it’s not bad enough to have to have an end cap strike it causes turbulence or something on one side of the aperture.
    Happens pretty often on the 22/45s from ruger
     
  10. js415

    js415 ODT Junkie! Supporter

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    I've got my Red Dot sighted in pretty well, and I think I'm going to give it another test or two to see what happens.

    Are there any tests I can do here at the house to see exactly what is happening?

    I'm not sure I know what the "Thread relief" and "shoulder" issues are or what to look at. Maybe I need to bring it by your shop one day and see what happens?

    Thanks,

    Jerry
     
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