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Author Topic: PS90 SBR with Suppressor POI Shift  (Read 7256 times)

Icer

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PS90 SBR with Suppressor POI Shift
« on: October 23, 2018, 12:42:07 pm »
I hardly comment on here, but I thought I'd ask my question here.

I have a PS90 that I Form 1'd into an SBR, TROS USA did the barrel, and I have a Specter II that I enjoy using on it. My optic is a Sig Romeo5 red dot. I've got a massive POI shift to the right (4-5 inches at 25 yards.) when I mount the Specter II to the barrel. I don't seem to have enough windage to change to match the new POI. Is there any particular thing that would cause that large of a shift? Does anyone have experience with that on these? Any solutions?

My ARs that I've mounted my Specwar 762, and my SRD556QD on don't have nearly the POI shift. That's why I'm this confused by the shift.
Nebraska

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    booksmart

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #1 on: October 23, 2018, 01:48:05 pm »
    Shoots straight without the Specter II?

    ynotaz

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #2 on: October 23, 2018, 06:30:11 pm »
    If you answer yes to the above question "yes",

    Then check all mounting surfaces.  Are you using any form of crush washer, which you probably shouldn't, is there any type of a suppressor QD mount on that rifle that is different than your ARs? 

    Last question which I hate to ask but, are the threads and shoulder concentric with the bore?  You may need a good Smith with tools or a good machinist to answer that question.
    Arizona

    Icer

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #3 on: October 24, 2018, 12:28:39 pm »
    Shoots straight without the Specter II?

    Yes. Shoots far to the right, and down, with both the iron "sight" and the Romeo5 with the can, shoots straight without.

    If you answer yes to the above question "yes",

    Then check all mounting surfaces.  Are you using any form of crush washer, which you probably shouldn't, is there any type of a suppressor QD mount on that rifle that is different than your ARs? 

    Last question which I hate to ask but, are the threads and shoulder concentric with the bore?  You may need a good Smith with tools or a good machinist to answer that question.

    No other mounting surface. Just the can to the barrel direct. Might have to take it to a former place of employment to check that info. I don't have nearly the number of tools for it.

    I did double- and triple- check the mounting hardware for the red dot to make sure it hadn't shifted, I have a solid mount on that.
    Nebraska

    booksmart

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #4 on: October 24, 2018, 01:01:48 pm »
    Have you shot with the red dot but without the can?

    Can you post photos of the barrel end, side profile and head on, with & without the can?

    Grant

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #5 on: October 24, 2018, 09:15:05 pm »
    I've never seen that drastic of a shift to the side.  Sometimes elevation.

      Is there any chance it is a teeny bit non-concentric and it's glancing off the edge of the can?
    Montana"I’d say the worst part of all this is the feeling of betrayal,           but I’m betting the part where they break in here and beat us to death might be worse.”

    booksmart

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #6 on: October 25, 2018, 09:17:12 am »
    I would think he would notice a baffle strike.

    Icer

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #7 on: October 25, 2018, 04:13:58 pm »
    I would think he would notice a baffle strike.

    Considering that I had an end cap strike on my SpecWar 762 (Silencerco has the best solutions "Hit it with a hammer to fix it."), I would, in fact, notice that.

    Have you shot with the red dot but without the can?

    Can you post photos of the barrel end, side profile and head on, with & without the can?

    I have. In fact had it zeroed in before adding the can because the can was in jail after I had already had the form 1 for a fair amount of time, and had the PS90 done for well over a year before I got the can. Had no issues prior to the can. I haven't shot it recently, but I've been thinking about it for a while - thus asking for once. I can snag some pictures later today probably.
    Nebraska

    booksmart

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #8 on: October 26, 2018, 08:41:14 am »
    Also shots from above...

    ynotaz

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #9 on: October 26, 2018, 12:38:22 pm »
    Barrel threads can be non-concentric with bore or the shoulder may not be cut perpendicular to the bore. 

    With a flash hider or muzzle brake, this would likely be meaningless.  With a suppressor it could cause baffle strikes or POI s___.  You can try putting a small mark on the suppressor and see if it will time differently on the threads.  If it will time to different location see if the POI shifts in a different direction based on which point the suppressor is timed. 

    One timing point may give you much less POI shift and could be acceptable to you without investing more in smithing.
    Arizona

    RetroGrouch

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #10 on: October 26, 2018, 11:39:25 pm »
    I'm assuming there isn't any contact between the silencer and any part of the gun other than the barrel, but how close does it get?  When a bullet passes through the barrel, if the silencer is close enough to a hand guard (for example) the barrel harmonics could cause enough barrel movement for the silencer to touch a hand guard and change POI.
    Arizona

    Grant

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #11 on: October 27, 2018, 09:54:24 am »
    I would think he would notice a baffle strike.

    I wasnt meaning enough for a full strike.  A local suppressor guy had one that wouldnt leave a mark...at first.  it took almost 100 rounds where it just BARELY wiped the coating off before you could see the strike mark.  It was just whispering off the edge.

     
    Montana"I’d say the worst part of all this is the feeling of betrayal,           but I’m betting the part where they break in here and beat us to death might be worse.”

    Icer

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #12 on: October 30, 2018, 10:17:34 pm »
    Looks like you might be right with the strike. Here's from the interior of the can, where the threads meet the barrel.













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    Nebraska

    AltRight Vanguard

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #13 on: October 30, 2018, 11:10:51 pm »
    Looking at your pictures, (and it is very difficult to see anything conclusively in pictures) it appears that your can *may* tilt to Port side a bit.  If (if) that is the case, it would pull the hole in the end cap toward the left side.  If it does, then you may be getting just a kiss of an end cap strike on the right side, and that may somehow be pulling the rounds off to the right.  It sounds backwards to me, but I am no expert on the matter.

    What do your groups look like at 25?  Nice an tidy, or a pattern?
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    ynotaz

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #14 on: October 31, 2018, 12:12:28 am »
    My mistake,  I thought you were mounting suppressor on 2 other weapons with no issues.  Looking at your pictures and rereading your initial post says not.

    It does look like the threads on the suppressor are buggered up which could cause a baffle strike.  The threads on the weapon look good.  Looks can be deceiving.  Can you bring both items to the guy that cut the barrel and threaded it for him to check it out?
    Arizona

    Icer

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #15 on: October 31, 2018, 08:45:13 am »
    Looking at your pictures, (and it is very difficult to see anything conclusively in pictures) it appears that your can *may* tilt to Port side a bit.  If (if) that is the case, it would pull the hole in the end cap toward the left side.  If it does, then you may be getting just a kiss of an end cap strike on the right side, and that may somehow be pulling the rounds off to the right.  It sounds backwards to me, but I am no expert on the matter.

    What do your groups look like at 25?  Nice an tidy, or a pattern?

    Nice and grouped. Far down and to the left.

    Dead on center without the can.

    My mistake,  I thought you were mounting suppressor on 2 other weapons with no issues.  Looking at your pictures and rereading your initial post says not.

    It does look like the threads on the suppressor are buggered up which could cause a baffle strike.  The threads on the weapon look good.  Looks can be deceiving.  Can you bring both items to the guy that cut the barrel and threaded it for him to check it out?

    Unfortunately I cannot, the work was done by TROS USA in Oregon, and I'm in Nebraska. I'm the only person I've met who is experiencing this issue with his work though, so I'm leaning towards suppressor issues. I might contact SilencerCo and see what they have to say.

    I can also get an additional QD mount for my SRD556QD and see if that shoots straight. But that may just cause issues.
    Nebraska

    booksmart

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #16 on: October 31, 2018, 08:49:47 am »
    I'd actually say it looks slightly down and right...  closer shots of the barrel threading (in the same perspectives) would be useful.

    Plus one to Grant for the endcap strike, though.  :thumbup1

    Grant

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #17 on: November 01, 2018, 01:09:51 am »
     Best of luck.  Keep us informed how it turns out.

    That is a nice looking gun, always thought the PS-90s with 16" barrels looked funny.  That  looks awesome with or without the suppressor.

     
    Montana"I’d say the worst part of all this is the feeling of betrayal,           but I’m betting the part where they break in here and beat us to death might be worse.”

    Icer

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #18 on: November 09, 2018, 05:04:00 pm »
    Just got off the phone with SilencerCo, and we figured out the issue.

    Issue is the length of the threads, it's too long and cut the O-ring on the mount, which caused the issue. They're shipping out a new o-ring for me free, and I'll be picking up a spacer for threads in order to prevent it in the future. A $16 fix to a potentially expensive problem.



    Best of luck.  Keep us informed how it turns out.

    That is a nice looking gun, always thought the PS-90s with 16" barrels looked funny.  That  looks awesome with or without the suppressor.

     

    Thanks! I enjoy it. It shoots better cut down too, the full barrels are goofy and just unwieldy.
    Nebraska

    Grant

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    Re: PS90 SBR with Suppressor POI Shift
    « Reply #19 on: November 09, 2018, 09:30:08 pm »
     Awesome!  Glad to hear it worked out.

     
    Montana"I’d say the worst part of all this is the feeling of betrayal,           but I’m betting the part where they break in here and beat us to death might be worse.”

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