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Gunsmithing Issue: Leupold Dual Dovetail on Winchester Model 70 .375 H&H Magnum

Tango down

Full Member
Full Member
Minuteman
Dec 2, 2011
775
43
Las Vegas, NV
Hi guys
I encountered an issue mounting a scope and I have a few questions on what could have been the problem. I installed several scopes on several rifles and never had an issue, all are tack drivers but all my stuff is "Tactical", such as Badger 35 MOA rails, Badger rings, S&B or NF scopes, TRG rifles, etc...you get the picture. This is the first time I play with a hunting rifle, hunting rifle scope and accessories.
I recently purchased a Winchester Model 70 Alaskan (solid Walnut stock) in .375 H&H Magnum. For optic, I chose a Leupold VX-3, 3.5-10x40mm, Boone & Crockett reticle. For rings and bases, I went with the Leupold Dual Dovetail system (.330 rear base).
I installed the front and rear bases, installed the DD rings, used the Wheeler adjustment kit to make sure everything was straight and slightly lapped the rings, to ensure a decent contact scope/rings, as the .375 H&H has a decent amount of recoil.
When I was done installing everything, I removed the bolt, to roughly bore sight the rifle (the old way, looking through bore), in order to match the reticle with the center of the bore, lined up on a target about 20 yards away.
The elevation was almost right on but the center of my cross hairs was about 20" off to the left. Long story short, I ran out of lateral adjustment before my cross hairs could meet with the center of the bore, on target. I turned the rings, even switched them in every possible way, hoping it would solve the issue but no such luck, I also checked the front and rear bases but not much to do there; I was careful tightening the rings screws in the proper order, to ensure adequate pressure on each side.
When I ran out of ideas, I contacted Leupold and a Tech referred me to their FAQ Customer Support Page.
This is what it says:

"4. My scope is running out of internal adjustment travel before I get properly sighted in. How can I obtain more travel?

When encountering an issue involving exhausted adjustment travel it is likely related to the alignment between the scope and barrel. When producing a firearm, there are many different components, each having a tolerance specification. As these tolerances “stack,” the alignment between the receiver and the barrel changes; this is why 10 seemingly identical rifles will all require different amounts of scope adjustment to sight-in. This is also why some scopes will reach the end of the adjustment travel without properly aligning to the bore; running out of adjustment before you can place the bullet in the center of the target.

This issue can be rather frustrating to the average rifleman
If an issue exists on the windage axis, the correction needs to be made with windage adjustable bases or rings. Leupold offers windage adjustable bases (STD) which have two windage screws holding the rear ring. By loosening one side and tightening the other, they shift the rear of the scope right or left. It should be noted that shifting the rear of the scope to the left will cause the point of impact to shift to the left and vise versa. It should also be noted that if one axis is near the limit of its adjustment, there will be a reduction in the amount of adjustment on the other axis. If the elevation adjustment is near the top of the adjustment range, the windage adjustment will be reduced; if windage adjustment has been induced, there will be a reduction in elevation adjustment. This can be illustrated by drawing a circle on a piece of paper to represent the maintube of a scope. If you start in the center of the circle with your pencil, you can move an equal distance in any of the four directions: up, down, left, or right. If you start in the center of the circle and move upwards toward the top of the circle, you will see that the distance remaining to the left and right has been diminished. The same is true in any direction; if you start in the center of the circle and move to the left, you will have diminished travel to adjust up or down."

So the explanation there is that all rifles are different and you may need adjustable bases, or rings? OK maybe but (I would assume) only up to a certain point, I never encountered this issue before; would this be a common thing on hunting rifles?

I since purchased the adjustable bases and the according rings, I will install these today and hope for the best. I will not lap the rings, just in case... ;)

Nevertheless, I am still not sure why the issue; I normally do not lap rings on any of my tactical set ups, so even though I was careful and did not remove much metal form the rings, I may have created the problem; could this be the reason why I ended up with this issue?
Another possibility would be the holes in the receiver not being lined up properly, or the some kind of alignment issue with the bases but Leupold and FN (now making the Win Model 70) are good companies with solid reputation and products, so I am not entertaining this idea too much.
It may not be easy to answer this question without taking a look at the rifle and bases/rings but if anyone has an idea on why I encountered this issue, let me know your thoughts. Even though I already purchased other bases and rings that will, hopefully, fix the problem, I would not mind learning something, especially if I made a mistake.

Thanks for your input and good shooting to all ;)
Ombre noire
 
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Are you talking about the Leupold base that has the two horizontal screws to hold the rear ring on? If so, those screws could possibly be adjusted off center, which would cause the problem you are describing.
 
Are you talking about the Leupold base that has the two horizontal screws to hold the rear ring on? If so, those screws could possibly be adjusted off center, which would cause the problem you are describing.

Hi nso123
The Leupold base, with the 2 horizontal screws to hold the rear ring on, is the "adjustable one", which I purchased in order to try to fix the problem. I had the issue with the "Dual Dovetail" rings and bases; I was not expecting any issue, as they have a good reputation among hunters.
 
Ok, so you are talking about the ones that the rings twist and lock into place. I have used those on several hunting rifles with no problems at all. I wonder if your screw holes in the receiver could possibly be slightly off?
 
Ok, so you are talking about the ones that the rings twist and lock into place. I have used those on several hunting rifles with no problems at all. I wonder if your screw holes in the receiver could possibly be slightly off?

Affirmative, they are called "Dual Dovetail ring and bases"; the screw holes in the receiver being slightly off is a possibility and I hope the Leupold adjustable rear base is going to fix the issue. I am now in the process of removing the DD (Dual Dovetail) bases and rings and I will give a shot to the "adjustable" kind.
I will post if it solves the issue, or not.
I hope it does, as one of my shooting buddies just bought a CZ 550, also in .375 H&H, same scope and we are going to have a friendly competition (kinda) between his CZ and my Win Model 70, just to see who out shot who. We usually do this with precision rifles but old habits die hard ;)
 
Hey there,
Yes the scope base screw holes in the receiver might be off but it seems unlikely. I fully agree with you on the quality of the FN/Winchester mod. 70. They are a VERY nice rifle. And you have it in 375H&H. That is an awesome caliber. Anyway, I was wondering could the screw holes in one or both bases be off center? Or could it be something to do with the base to receiver bearing surface being off a bit and causing the rings to be slightly canted? I hope everything works out for you. You definitely have a perfect "hunt anything" rifle.
Have a good day.
 
Hey there,
Yes the scope base screw holes in the receiver might be off but it seems unlikely. I fully agree with you on the quality of the FN/Winchester mod. 70. They are a VERY nice rifle. And you have it in 375H&H. That is an awesome caliber. Anyway, I was wondering could the screw holes in one or both bases be off center? Or could it be something to do with the base to receiver bearing surface being off a bit and causing the rings to be slightly canted? I hope everything works out for you. You definitely have a perfect "hunt anything" rifle.
Have a good day.

Hi Ballistic Artist
That is another possibility (base screw holes being off), I also checked and cleaned the receiver bearing surface (and base) but it is tough to tell what is off, just by looking at it. I also cleaned the receiver's holes with a cue tip and, I think, did everything by the book. We'll see how it goes with the new stuff...Yeah, I dig the new rig, strong caliber. I shot plenty of times 338LM and 45/70, no small rigs by any means but the .375 is different, still very tolerable but you learn to respect the caliber, or it will send you a little "reminder". It is a "hunt anything rifle", that's one of the reasons we went with the .375 H&H. I think my buddy's CZ kicks more than the Mod. 70 but we will double check on that, as I know we will switch rifles at one point, or another, for our "friendly challenge".
Thanks for the good words ;)
 
Looks like the "adjustable rear base" did the job, I'll go to the range soon, probably Monday and will fine tune it.
As the scope was still tilted left after installing the new bases and rings and making sure the rings were aligned straight, I would go for the alignment of the screw holes on the receiver being slightly off.
If anyone experienced something similar, please post it, so other guys with similar issues won't have the same look on their faces that I had when I ran out of adjustments ;)
I will post something after the range session, just to make sure it's all good.
Good shooting to all.
Ombre noire