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Old May 16th, 2018, 11:51 AM #1
ras_oscar ras_oscar is offline
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Mounting my scope: is this usual?

Mounted my Nikon M308 scope with a single piece mount to my new Ar10. The first trip to the range, altitude was near dead nuts on. However, it was shooting far to the left: like 8 inches at 25 yards. Is this usual? should I be reassessing the process of mounting the scope to the picatinny rail? I don't want to take up all available windage adjustment just to get it to zero.
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Old May 16th, 2018, 11:54 AM #2
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You have a few options....if you can dial the 8" to bring it back right and still have a few MOA to move to the right you'd be ok.

2nd option is to lap the rings, there is a chance that the rings aren't aligned correctly.

I don't think its that unusual personally, I've seen worse.
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Old May 16th, 2018, 11:57 AM #3
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Quote:
Originally Posted by ras_oscar View Post
Mounted my Nikon M308 scope with a single piece mount to my new Ar10. The first trip to the range, altitude was near dead nuts on. However, it was shooting far to the left: like 8 inches at 25 yards. Is this usual? should I be reassessing the process of mounting the scope to the picatinny rail? I don't want to take up all available windage adjustment just to get it to zero.
It's actually quite fortunate you got on paper the first few rounds. 8" is fine; I've had to hold off the target frame sometimes with scopes mechanically at 50% adjustment from the factory.

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Old May 16th, 2018, 12:04 PM #4
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just double check that everything is right (scope not twisted/canted/crosshairs vert and horiz, mounted squarely and securely to the rail, etc). how much room do you have to dial right and left after you've zeroed at 100? maybe take a pic or two from each side so we can see if any obvious issues. could be as simple as the scope wasn't set to zero when you got it.
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Old May 16th, 2018, 01:12 PM #5
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8 inches at 25 yards is 32 MOA. The max internal adjustment is 40 MOA. That is at the edge of acceptable*. You can still be on paper at 100 yds, but I would definitely re-assess the mount to make sure its square.

*If "like 8 inches" means 10 inches, you wont be able to zero it.
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Old May 16th, 2018, 01:40 PM #6
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Be sure the reticle is properly centered in it's range of travel. Check the mount for any obvious alignment or fitment issues. Remove the BCG and boresight to insure that the bore and scope reticle align to the same point. If they are not reasonably close, you probably have other issues to examine. It may be possible that the receiver face needs to be trued or that the mount is not machined correctly. Be sure to check the mount for burrs left over from the machining process. Worst case, contact a smith, like Clandestine.
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Old May 16th, 2018, 01:42 PM #7
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May sound silly, but are the dials centered and not cranked to one side?

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Old May 17th, 2018, 07:12 AM #8
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Quote:
Originally Posted by dist1646 View Post
Be sure the reticle is properly centered in it's range of travel.
This. In fact, when mounting any new scope for the first time, you should do this, because you don't know how it was adjusted before you got it. Crank the windage all the way over to one side. Then crank it all the way to the other side, while counting clicks. Then crank it half that number of clicks back in the original direction. Do the same thing with elevation. After that, you can be sure that the scope is set to reasonably near the center of its range of adjustment.

After that, you can check all of the other stuff.
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Old May 17th, 2018, 02:05 PM #9
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Because I fret over details, I also contacted the manufacturer. They told me the scope has 80 clicks of adjustment in all 4 directions. I never thought to verify it shipped in the middle of the range. I have a bore sight on order and will start with that. Get it to zero in the basement, set that to zero on the turrets and then count to the stop. If it's 45 or more, I'm good. If its less, i'll reset the turrets to center both directions, then shim the rings to approximate zero and start again.
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Old May 17th, 2018, 08:02 PM #10
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don't need a bore sight. just pull the upper off the lower and pull the bolt and handle out. set it on something sturdy or sandbags etc, on your kitchen table or picnic table or somewhere where you can look out 50-100 yds. look thru the barrel and find a 'target' out there (soda can, top of fencepost, knot in a tree) and center that in your barrel. then just turn your scope knobs until they're on the 'target.'

i wouldn't zero your knobs at that point, just counts clicks left and right and up and down, and if you have plenty of room on each side, you should be GTG. then hit the range, fine tune your zero and then zero the knobs.
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