Inconsistent POI with suppressor

Sonnystults

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Oct 31, 2019
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I am running a sandman L can on a seekins havak bravo 6.5creed, using the deadair keymo qd system. I am noticing a .75-1 moa poi shift between shooting sessions where I remove and reinstall the can between sessions. My usual practice is transport rifle unsupressed in its case, install suppressor while setting up to shoot, shoot match or finish hunting session, remove can transport and store unsupressed.

I may be expecting unrealistic consistency out of a qd system but I feel like as long as I'm keeping the carbon build up removed from the taper on the locking ring I should be seeing pretty consistent results from session to session. I have googled and came up empty on information so anything anyone can provide will be greatly appreciated.

Considering just going to direct thread but would like to identify the issue I am seeing with current setup before i jump on another suppressor purchase.
 

Sierra770

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Just to clarify. Are you saying your Zero changes (like a wondering zero) each time you take it on and off or that there just is a poi shift?
 

Sonnystults

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Oct 31, 2019
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I apologize I am not sure that I understand the difference in those. I can shoot for group w can attached. Hit exactly where Im aiming, remove can, reinstall, no longer hit exactly where I'm aiming. Usually jumps back and forth between dead on or .75-1 high and .5-.75 right
 

Sonnystults

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Oct 31, 2019
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Just to clarify. Are you saying your Zero changes (like a wondering zero) each time you take it on and off or that there just is a poi shift?
Ahh re read the question. Correct wondering zero. I am well aware of the initial poi shift between unsupressed and suppressed. That isnt what is bothering me. Sorry about that
 

chevy_man

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I've never seen a QD system I would use for precision. Every single wandering zero I've seen with a can was QD mounted.

I use direct thread and still witness mark the barrel and can so I know it's spun on the same every time.
 
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ken226

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I use a Griffin Armament shorty QD brake and homemade form 1 suppressor. It repeats consistently. But, it threads on, against a taper, so it always locks up at the exact same spot. I marked the suppressor with a center punch so I can make sure it indexes the same every time.

dell laptop spacebar problem

My suppressor zero is .1 mil up and .1 mil left from unsuppressed zero, since the day I manufactured it 3 years ago.

It looks like your Sandman L suppressor mount uses a 3 lug mount and spring system to pull the tapers into contact.

If you havn't already, try marking the suppressor so that your are engaging it in the same orientation (clock position) each time. For consistency sake, you want the same male lugs engaging the same female lugs, and locking up in the same clock position every time.

In the engineering and manufacturing world, zero, is an imaginary number. It's asymptotically impossible to reach when setting up a part in a lathe. So, you have to assume some small amount of axial and radial runout in the system.

If the suppressor clocks to a different position each time you mount it, the little runout errors are in a different spot every time.

For accuracy (repeatability), it's desirable to have a rock solid lockup in the same orientation every single time you mount it.

Since your Sandman is a 3 lug mount, with 120° seperation between lugs, there are 3 possible clock orientations it can end up in.

Each orientation would have it's own zero 😁. I would just pick one, and put it on in that orientation every time.

If you've already been doing that, then disregard everything I said..
 
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Pvt.Donut

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I use a Griffin Armament shorty QD brake and homemade form 1 suppressor. It repeats consistently. But, it threads on, against a taper, so it always locks up at the exact same spot. I marked the suppressor with a center punch so I can make sure it indexes the same every time.

dell laptop spacebar problem

My suppressor zero is .1 mil up and .1 mil left from unsuppressed zero, since the day I manufactured it 3 years ago.

It looks like your Sandman L suppressor mount uses a 3 lug mount and spring system to pull the tapers into contact.

If you havn't already, try marking the suppressor so that your are engaging it in the same orientation (clock position) each time. For consistency sake, you want the same male lugs engaging the same female lugs, and locking up in the same clock position every time.

In the engineering and manufacturing world, zero, is an imaginary number. It's asymptotically impossible to reach when setting up a part in a lathe. So, you have to assume some small amount of axial and radial runout in the system.

If the suppressor clocks to a different position each time you mount it, the little runout errors are in a different spot every time.

For accuracy (repeatability), it's desirable to have a rock solid lockup in the same orientation every single time you mount it.

Since your Sandman is a 3 lug mount, with 120° seperation between lugs, there are 3 possible clock orientations it can end up in.

Each orientation would have it's own zero 😁. I would just pick one, and put it on in that orientation every time.

If you've already been doing that, then disregard everything I said..
The 3 lugs are not identical on the sandman and it only index at 1 position. I have a Sandman S and never had any issues with POI shift when installing and removing the can. OP, if you haven't, reach out to Dead Air and see if they have any insight. First, you installed the muzzle device with shims correct? Make sure everything is tight. Make sure your scope rings, base, etc. are mounted correctly and tight.

Do you have POI shift unsuppressed? Test out some things and see if you can narrow it down to a certain step causing the issue.
 
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gasrat

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I run into the same issue with a QD mounted Yankee Hill Phantom. Can indexes back to the same spot every time, but if I zero with the can on, remove it, then put it back on, my POI moves up to 1:00 every time. I just found a carry bag that will allow me to carry my rifle without removing the can and I just leave it on all the time. Contacted YH about it and they said it shouldn't do it. Told me to tighten the can down to almost bottomed out, then ratchet it on with a quick, hard twist. I've tried that also but it doesn't resolve the issue. So, again, I just leave it on.