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.
Mounting my scope: is this usual?
- Thread starter ras_oscar
- Start date
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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.
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.
VeryTraumatic
Member
- Dec 24, 2014
- 1
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.
Sent from my SM-G965U1 using Tapatalk
davsco
Ultimate Member
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.
danb
dont be a dumbass
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.
*If "like 8 inches" means 10 inches, you wont be able to zero it.
dist1646
Ultimate Member
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.
Hawkeye
The Leatherstocking
- Jan 29, 2009
- 3,971
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.
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.
davsco
Ultimate Member
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.
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.
davsco
Ultimate Member
again, maybe attach a few pics there. if there is something wrong with your setup, sure someone here will see that and let you know...
Major03
Ultimate Member
Sometimes the barrel extension isn’t square to the upper receiver and the barrel will sit a little cockeyed.
This throws off iron sights, and is probably what is throwing off your scope.
Bottom line, it might not be a problem with the scope but the upper.
Brownells makes a lapping tool the will square it, or it’s an easy job for a gunsmith.
This throws off iron sights, and is probably what is throwing off your scope.
Bottom line, it might not be a problem with the scope but the upper.
Brownells makes a lapping tool the will square it, or it’s an easy job for a gunsmith.
I'll take a few pictures of the scope mounted on the rifle. Any specific detail shots recommended in addition to the overall left/right/top/bottom?
I found that my elevation setting is within a few clicks of the stop, so I know I have some work to do. I assume I *could* shim the front or rear between the scope and the mount, but I'm not sure how I would shim to adjust windage. I counted at least 150 clicks of windage in one direction before I gave up and returned to zero.
As a reminder, I am using a Nikon M308 One piece scope mount. I *assume* the front and rear rings would be lapped in the factory far more precisely than I could accomplish using hand tools and a vice.
Major03
Ultimate Member
Personally, I'm not a fan of the shimming method to correct a poorly aligned scope. I think you'd be better served by figuring out what the underlying cause is and fixing that.
My bet is the following in order:
- out of square upper to barrel extension causing the barrel to be off center to the upper / bolt face. Fixing this BTW should make things a touch more accurate too
- scope base is jacked up, replace if needed
- rings are jacked up, if so they can be lapped to fix that problem.
- scope is jacked up, replace if needed
My bet is the following in order:
- out of square upper to barrel extension causing the barrel to be off center to the upper / bolt face. Fixing this BTW should make things a touch more accurate too
- scope base is jacked up, replace if needed
- rings are jacked up, if so they can be lapped to fix that problem.
- scope is jacked up, replace if needed
This your nikon mount? Specifically, the TWO separate rail clamps. That one is *TOTAL SHIT*. I had the 223 version. It will not auto center and you can easily tighten it down w/ the center part not parallel to the pictinny rail. Prove it to yourself: Loosen the clamps, twist it w/ the scope grossly to one side (windage), and re tighten. It will still visibly retain a lot of the offset. You could probably get it close enough centered to work, but I always worried about it holding zero. If you do have that kind of mount, my suggestion is to throw it in a deep lake and get a different mount. One that has one side of the rail integrally machined w/ the upright part. Nikon makes some mounts made correctly, but they still sell that crap 2-pc clamp type in both 223 and 308 variants
Attachments
That's the mount, with the 2 piece clamp. I will try returning the reticle to the midpoint both directions and then try messing with the 3 screws to see if I can get it closer. Assuming I am forced to replace the mount, Is there a better one piece mount for 308?
quad
Another Hooligan
Burris PEPR is a great mount
danb
dont be a dumbass
Leupold and Warne both make good 1pc mounts. I have 1 pc Warne on some rifles, never had a problem. Warne XSKEL1 gen 2 (1 in) and XSKEL30 Gen2 (30mm) both come in colors too. Send it in style.
Major03
Ultimate Member
LaRue makes a great mount if you don't care about dropping some coin. Burris PEPR is a good mount if you're more concerned with how much you're spending. I have both.
The Burris is heavier.
The Burris is heavier.
- Jul 29, 2014
- 49,963
This your nikon mount? Specifically, the TWO separate rail clamps. That one is *TOTAL SHIT*. I had the 223 version. It will not auto center and you can easily tighten it down w/ the center part not parallel to the pictinny rail. Prove it to yourself: Loosen the clamps, twist it w/ the scope grossly to one side (windage), and re tighten. It will still visibly retain a lot of the offset. You could probably get it close enough centered to work, but I always worried about it holding zero. If you do have that kind of mount, my suggestion is to throw it in a deep lake and get a different mount. One that has one side of the rail integrally machined w/ the upright part. Nikon makes some mounts made correctly, but they still sell that crap 2-pc clamp type in both 223 and 308 variants
A bad idea borrowed from Millet. Stupidest design ever!
