High end rifle scopes?!

[BullfrogKen]

Yup, those are my thoughts, too.


Something about your rifle is giving you some negative elevation. Try doubling up on that 20 MOA base with a set of Burris rings and the inserts.

 

[Jasper1573]

It is possible the barrel and/or receiver are not true.

I don't believe this to be the case because there has never been an issue before, but

Something about your rifle is giving you some negative elevation.

there is something going on that I can't quite figure out. The range of the scope is as advertised, and it is mounted properly. I am a mere 5 or 6 minutes of angle short of the adjustment range that I need. I will ponder this further.

Any helpful thoughts are appreciated at to what could be the cause.

Cheers,

Jasper

 

[atblis]

I recently purchased a Zeiss Conquest 6.5-20x50mm scope. Great scope...near perfect tracking around a 20MOA box, clear glass, etc.; except, after zeroing the scope at 100 yards I found I only had about 25 MOA upward elevation adjustment with a 20 MOA base...and that won't get me out to 1000 yards with a .308 Win without combining scope adjustment and mildots...a complex mental calculation when taking windage into account as well. So, I unfortunately had to return the scope.

This wasn't a similar issue?

 

[CharlieDeltaJuliet]

I am shooting past 1200 with the new Bushnell Tactical Elite, it has 90 MOA on it though. It is mounted on a 50 bmg with a 20 MOA cant. rail on it. When ordering I almost made the mistake of ordering the 6500 (40moa) but that was my own fault. I think Bushnell might have even upped the adjustment on the newer one though. I paid around the same as you though.

 

[Jasper1573]

atblis,
Yes, that was a similar issue; however, there was a bold type note in the Zeiss Conquest owners manual that state a 20 MOA base is required to achieve the full elevation range of that scope, and sure enough, with my 20 MOA base I had the advertised elevation range of the scope.

But with the NF, there is no such note to the user. I checked the base to ensure it is indeed snugly fitted to the receiver, and sure enough it is. No issues or obstructions with the rings where they fasten to the rail.

So I have gone the not-so-cheap route and ordered a NF 40 MOA base. I had another 20 MOA base on order from Larue so I cnx'ed that, and I am only out another $40.

I am going to the range today to shoot this set up and see how it performs at 300 yards.

 

[Jim Watson]

A friend had that problem. Careful measurements showed he actually had about a 17 MOA base which did not help. He sent it back and the maker remachined it to the maximum taper its thickness allowed, 28 MOA. That was enough for 1000 yards but it got tight at 1200.

A 40 MOA base will probably not let you zero at 100 yards. So what?
Said friend shoots close range for ammo checks at a "thermometer target", a tall piece of paper with a 5 MOA aiming point like a bullseye near the bottom and a scale running up the target so he can see the elevation for various longer ranges.

 

[Jasper1573]

A 40 MOA base will probably not let you zero at 100 yards. So what?

I keep this particular rifle zeoed at 300 yds primarily for target shooting, and when I hunt with it, I put on a different scope with a lower power range, but I keep that zeroed at 300yards also. At 100 to 200 yards, the bullet is 5 to 6 inches high, so I aim at the lower third of the deer's chest.

 

[atblis]

Zeiss put that comment in because the scope has a limited elevation adjustment range. It's otherwise no different than any other scope. The scope has no clue if it's on regular or 20 MOA bases. By full range, they mean 40 MOA, not 20 MOA. There's something wrong with your rifle and/or the mounts. Are you sure you have a 20 MOA base? Perhaps it was mislabeled/mispackaged by the manufacturer.

 

[Jasper1573]

Zeiss put that comment in because the scope has a limited elevation adjustment range. It's otherwise no different than any other scope. The scope has no clue if it's on regular or 20 MOA bases. By full range, they mean 40 MOA, not 20 MOA. There's something wrong with your rifle and/or the mounts. Are you sure you have a 20 MOA base? Perhaps it was mislabeled/mispackaged by the manufacturer.

Concerning the Zeiss Scope, it had a total of about 25 MOA up and down for a range of about 50 MOA, but that meant without the 20 MOA base, it would have only had 5 MOA upward elevation. But that scope is history now.

Now I am in some agreement, there is something wrong somewhere and I just can't quite figure it out. While at the range today, I changed out the Larue rings for some Burris Xtreme tactical rings I had in my tool kit, and it really didn't change anything. Also, it seems as if something is warped or out of alignment with the scope and the mount/rings as you stated above.
I am sure the 20 MOA base from Larue is labeled as a 20 MOA base because it is clearly printed on the side, and I can tell there is a definite downward cant from rear to front, but no I can't definitively say it is exactly 20 MOA.

Still perplexed and searching for a solution. I may take the whole thing apart tonite and put it back together. I have seen that work in other situations where the problem seems to eliminate itself when everything is dis- then reassembled.

 

[atblis]

There is no amount of adjustment that is allocated solely to up or down by the scope. It's simply elevation adjustment. You can bias it using different mounts. Zeiss means that to have the 50 MOA available for up adjustments, you'll need a 20 MOA base.

Notice that you're missing about the same amount of up elevation adjustment despite having switched scopes.

With the Zeiss 25 MOA+20 MOA= 45 MOA, Observed 25 MOA, Difference 20 MOA
With NF 32 MOA+20 MOA = 52 MOA, Observed 32 MOA, Difference 20 MOA
This assumes the scope is centered at the zeroed range.

 

[Jasper1573]

Notice that you're missing about the same amount of up elevation adjustment despite having switched scopes.

With the Zeiss 25 MOA+20 MOA= 45 MOA, Observed 25 MOA, Difference 20 MOA
With NF 32 MOA+20 MOA = 52 MOA, Observed 32 MOA, Difference 20 MOA
This assumes the scope is centered at the zeroed range.

Yes, that is what I have been trying to say...I am baffled as to why that 20 MOA base doesn't seem to have the intended effect. It is as if it is a flat base and doesn't add anything to the elevation adjustment range of the scope.

Prior to the Zeiss and the NF scopes, I used a Sightron SIII which has 100+ MOA of elevation, so whether the 20 MOA base had any effect is hard to say because the scope had so much elevation adjustment all by itself.

Does anyone know how to determine whether the cant of a 20 MOA base is actually 20 MOA? I understand the math, but it is the method of measurement that might prove difficult.

 

[atblis]

Compare the location of the crosshair between having the scope mounted forward and flipped around in the mount (no adjustments made, just flipping the scope around in the mount). Just need to put the base on the same flat surface both times. The reference surface doesn't have to be level, just the same for both cases. Use a vertically gridded target.

 

[Jasper1573]

Well, I ordered a NF 40 MOA base and that provided 20 MOA of "additional" elevation adjustment than I had with the 20 MOA base. I also changed out the Larue rings for a pair of Burris Xtreme rings.

At a minimum, I now have 52 MOA of upward adjustment remaining on the scope with a 300 yard zero. I don't think there was anything wrong with the Larue mount and rings nor do I believe there is anything screwed up about my rifle...it was simply zeroed at the middle of the range for both the NF and Zeiss scopes mentioned previously. Everything is operating properly now with plenty of windage and elevation adjustment.

I do think that a 40 MOA base seems a bit excessive, but NF makes them for a reason.

Thanks for all of the info and inputs and thoughts. I may try out another stock on the rifle and see if that has any effect, but for now everything seems to be working well.

 

[LAL357]

hey jasper this is larry are you aure you have the 20moa base facing in the right direction ? with that 40moa base you might want to set up at 100 and 200 yds also to see if you can adjust down for them or what your hold under will be so you will know when we shoot the backwoods matches next year.
the only reason i went with the sightron III 10x50x60 lrir moa2 scope was i was worried about being over the f t/r limit since i want to start shooting other place that might have sanctioned matches. iwas worried with the weight of the NF scopes it would put me over the limit.
if its really bad mirage (mostly on our range becuase of the gravel down range in front of the targets) i turn it down to 35-40 power (only had to go below that once this year) other than that i leave it up on 50 and shoot thru the mirage.i did notice that going with a better/higher magnification scope my scores have gone up it could also be the crosshairs i think that is why i'm only shooting in the mid 180's on my 6.5 creedmoor i'm using the old bushnell elite 4200 8x32x40 that was only my 308 when i started shooting your matches.