Windage limit

TraumaControl

Private
Minuteman
Dec 7, 2018
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Relatively new to precision shooting and scope mounting. So far shooting 1MOA with a 45-70 Marlin 1895 SBL with a Vortex crossfire 1-4 and an AR-15 with Eotech Vudu 1-6. I felt I was familiar enough with fundamentals and wanted to get into longer range and a bit more precision. Got a Ruger Precision Rifle for Christmas and just bought a Burris XTR II 8-40x50mm. Scope mounts provided by my cousin are Aero precision Ultralight weight 34mm mount. I took it to the range today and bore sighted at 25 yards and noticed the reticle was way off to the right from what I saw through the bore. This concerned me but I pressed on after adjusting the reticle to the target. Took a shot at 25 yards and point of impact was about 3 inches to the left of point of aim. Confirmed with 4 more shots with same results. Scope adjusts in 1/8 MOA so I (and correct me if I am wrong here) figured 8 clicks per MOA at 100 so 16 click per MOA at 50 and 32 click per MOA at 25 yards. This meant 96 clicks to correct and of course I hit the limit of windage adjustment and only able to get the 25 yard shot 1.5-2inchs to the left from point of aim. Took a shot out at 50 yards and as expected all of the shots were 5-6 inches to the left of the point of aim. I thought to myself damn this day would have been great if the awesome groups were actually where I was aiming. I didn't bother to take it out to 100 as the results were predictable. I just need help trouble shooting this now.

Is it the mount?

Is it the scope? ( I am currently reading and re-reading the manual and looking up detailed spec on scope)

Is it the rail on the rifle?

Do I just suck?

Any tips?
 

ShtrRdy

Gunny Sergeant
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Sep 17, 2011
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The good news is you probably don't suck. That is just way off. Next, we have to figure out what's not right.

Is it possible to borrow a scope, with rings, from your cousin to see if it does the same thing?

Do you have a straight yard stick? You could take the scope off the top and then lay the yard stick on top of the scope rail and lined up with the mounting holes, the eye-ball the barrel and yard stick to see if they are parallel to each other.
 
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Milo 2.5

The Dalai Lama of the Reload
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Aug 7, 2014
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The good news is you probably don't suck. That is just way off. Next, we have to figure out what's not right.

Is it possible to borrow a scope, with rings, from your cousin to see if it does the same thing?

Do you have a straight yard stick? You could take the scope off the top and then lay the yard stick on top of the scope rail and lined up with the mounting holes, the eye-ball the barrel and yard stick to see if they are parallel to each other.
I think ^^^ he nailed it.
I had an issue similar with a 9422, I ended up shimming the back ring. But you can buy Burris rings, I think they are called signature, they have inserts, they rotate 360 deg, giving left-right, up-down or a combo of either. This may be the easiest.
If you do buy them, first zero the reticle in scope, to maximize travel.
 

TraumaControl

Private
Minuteman
Dec 7, 2018
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So I used a laser level that had laying down in the garage and passed the laser through the base screws and onto the barrel. To me it doesn't look like the barrel is centered. What should I do about this?
 

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Milo 2.5

The Dalai Lama of the Reload
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Aug 7, 2014
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Gillette, WY
I think your best bet in mounting options would be for the optic to follow the barrel, through shimming or whatever.
 

bax

Sergeant
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Oct 25, 2009
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3 inches left at 25 yards is about 12 inches left at 100 yards. That is a lot. You shot groups so the gun is apparently tight:
  • barrel tight to the front of the receiver,
  • base tight on the receiver,
  • scope rings tight to the base,
  • scope tight in the rings.
Your neat trick with the laser suggests that the barrel points off to one side. That might happen if the barrel is tight but isn't correctly installed or if the barrel or receiver have a manufacturing flaw. Nobody is perfect but the RPR is a quality piece of gear so the idea that it is made wrong strikes me as unlikely but not impossible. That it is assembled incorrectly is more likely.

If you don't mind, let's start at the beginning:
  • pull the scope and rings off the weapon
  • pull the barrel
  • if the scope base is not integral to the receiver, pull that - I don't recall on an RPR.
  • remove the rings from the scope
  • recenter the windage on the scope -
    • carefully crank the windage knob all the way right
    • carefully crank windage all the way left keeping track of the minutes.
    • divide the minutes range in half
    • crank back to the center.
  • if the base is separate, carefully reinstall the base. I lay it on the receiver, loosely install the screws, wiggle it around to be sure that it is centered then start torquing the screws. I use Badger base and torque it to 15 inch-lbs. It is possible that the screw holes for the base are not aligned correctly. Small errors here may have a large effect but are very difficult to see. Be sure to use the correct torque for your base.
  • carefully reinstall the rings on the base. Be sure to push them forward against the front side of the slot and be certain they are not bound up or stuck in some odd position. I use Badger rings with a 1/2-inch nut on the left side. Tighten to 65 inch-lbs. Be sure to use the correct torque for your rings.
  • If you use abrasive and a grinding rod to make sure that the scope channel is aligned correctly, do that now. This will also check the ring alignment.
  • lay the scope in the rings, lay on the caps, tighten evenly. Be sure to use the correct torque for your rings.
Try to boresight at 25 yards. if the barrel boresight points to X and so does the scope, problem solved. Shoot and adjust to zero, slip turrets, rock and roll.

If the barrel boresight points to X but the scope points 3 inches left of X, you carefully tore it down and reassembled it so lets find the issue.

The scope points 3 inches left. Pull your scope and rings and put a known good scope and rings on the base. This tests if your scope and rings are good. Then using a good scope and rings replace the base and check again. Then check the barrel to receiver fitting. If there is a problem here this will probably have to go back to the factory to check and repair.