Elevation left on new scope

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VinceMarksman

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got myself a burris xtr 2 5-25 scope that has 90 MOA of elevation travel. I mounted it on a 20 MOA base on my tikka t3 and zerod it at 100y.

After the zero procedure I have 55 MOA of upward adjustment left. Does that sound normal with a 20 MOA base? I would have thought I would have a bit more left...

I might go to a ELR event with this rifle (308 win) and I will need quite a bit of elevation travel.

thanks for your feedback
 
That sounds about right. In a theoretical perfect world it would be 45 plus 20 for 65, but you used 10
of that sighting in. It could have gone the other way, but it didn't.
 
Depending on your definition of ELR, you're going to have to hold over. 55 moa works out to roughly 16 mil which gets my 20" .308 @2550 fps out to about 1150 yards. I get 17.5 mil of elevation from my scope and I was good for every long range target in the 1100s at the finale for the league I shoot in but had to hold over for the furthest which was 1280. At 1400, which is as far as my I have my tables set, I'd need 24.1 mil so I'd be holding over 6.6 mil, that's pretty significant, haha.
 
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You can shim the rear of the base. Without getting into the math it works out close to every .001" of shim being 1 MOA.

Before you start shimming things, there's something you should check. With only the front mounting screws installed hold it up to the light and see if you can see a sliver of daylight between the rear of the base and the action. A little is a lot in things like this, and it can be rectified by bedding the rail. Even if there's no gap, remedial shimming and bedding will get you some more elevation. Something else to consider is that windage affects total elevation travel. If the windage adjustments aren't centered
the erector assembly will bottom out in the scope tube that much sooner.

OR; you could just shoot it. You don't know that that 55 MOA is real until you prove it. Get a big target or a sheet of plywood and test what the adjustments really move the POI. A recurring theme in long range shooting is to not believe anything you can't prove.
 
Thanks guys

At 25 power I can holdover 24 MOA. Im still testing my sierra 175 TMK load so not sure of speed and drop pass 1000y. That gives me 79 moa of elevation including the holdover.

My front ring is completely at the end of the rail. The rail was cut at the tip to fit a cadex chassis. Im going to verify if the base is flat and perhaps back off the rings 1 slot

Edit: i wanted burris signature rings but they are not available at the moment in 34mm. All sellers have them back order
 
VinceMarksman said:
Thanks guys

At 25 power I can holdover 24 MOA. Im still testing my sierra 175 TMK load so not sure of speed and drop pass 1000y. That gives me 79 moa of elevation including the holdover.

My front ring is completely at the end of the rail. The rail was cut at the tip to fit a cadex chassis. Im going to verify if the base is flat and perhaps back off the rings 1 slot

Edit: i wanted burris signature rings but they are not available at the moment in 34mm. All sellers have them back order
Click to expand...


why use rings on a precision rig? to save money?
do yourself a favor and buy a nice QD 1 peice
 
VinceMarksman said:
Thanks guys

At 25 power I can holdover 24 MOA. Im still testing my sierra 175 TMK load so not sure of speed and drop pass 1000y. That gives me 79 moa of elevation including the holdover.

My front ring is completely at the end of the rail. The rail was cut at the tip to fit a cadex chassis. Im going to verify if the base is flat and perhaps back off the rings 1 slot

Edit: i wanted burris signature rings but they are not available at the moment in 34mm. All sellers have them back order
Click to expand...

Moving back 1 slot isn't going to change anything. The only real solution is to have a +30 or +40 rail either ordered or made.
 
Dogleg said:
You can shim the rear of the base. Without getting into the math it works out close to every .001" of shim being 1 MOA.

Before you start shimming things, there's something you should check. With only the front mounting screws installed hold it up to the light and see if you can see a sliver of daylight between the rear of the base and the action. A little is a lot in things like this, and it can be rectified by bedding the rail. Even if there's no gap, remedial shimming and bedding will get you some more elevation. Something else to consider is that windage affects total elevation travel. If the windage adjustments aren't centered
the erector assembly will bottom out in the scope tube that much sooner.

OR; you could just shoot it. You don't know that that 55 MOA is real until you prove it. Get a big target or a sheet of plywood and test what the adjustments really move the POI. A recurring theme in long range shooting is to not believe anything you can't prove.
Click to expand...

Windage affects elevation? Tell me more. I have a scope where the manufacturer claimed a 50 moa adjustment range. Wheni actually counted it came out to 133 moa. Seems too good to be true
 
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Windage can limit elevation adjustment. Picture a tube inside a tube. The inside tube is your erector assembly; which amoung other things carries the reticle and allows for adjustment. If the erector tube is centred side to side it has the maximum amount of movement possible before hitting the top and bottom of the main tube.

When a lot of windage adjustment is used just sighting in the erector tube is pushed toward the side. Because of this, the upward and downward movement is limited because it hits the main tube sooner. Sort of like trying to stand up in an igloo or tent, best be in the middle. The analogy is backward because down is up in a scope, but you get the idea.


Your scope having vastly more adjustment than it is supposed to really sounds like you got the wrong specs somehow.
 
Dogleg said:
Windage can limit elevation adjustment. Picture a tube inside a tube. The inside tube is your erector assembly; which amoung other things carries the reticle and allows for adjustment. If the erector tube is centred side to side it has the maximum amount of movement possible before hitting the top and bottom of the main tube.

When a lot of windage adjustment is used just sighting in the erector tube is pushed toward the side. Because of this, the upward and downward movement is limited because it hits the main tube sooner. Sort of like trying to stand up in an igloo or tent, best be in the middle. The analogy is backward because down is up in a scope, but you get the idea.


Your scope having vastly more adjustment than it is supposed to really sounds like you got the wrong specs somehow.
Click to expand...

Cool. Great illustration. Maybe the specs advertise a minimum elevation range of 50 MoA. According to your explanation, maybe they guarantee 50 MoA at the extremeedge of the windage knowing that if windage is centred its much more.

I definitely dont havethe wrong specs. Both bushnell website, manual and turrets are labelled 1/4moa per click. 15 MoA per full revolution. 2 moa short of 9 full revolutions. 133 MoA. Website and manual says adjustment range is 50"@100yrds, which is consistent for other scopes of similar mag power and size. 25mm tube.

Only thing that makes sense to me is if the listed adjustment spec is a guaranteed minimum and having much more than that is common, or this scope was built wrong.

This conversation makes me want to pull all my scopes out and test them.
 
Cameron SS said:
I definitely dont havethe wrong specs. Both bushnell website, manual and turrets are labelled 1/4moa per click. 15 MoA per full revolution. 2 moa short of 9 full revolutions. 133 MoA. Website and manual says adjustment range is 50"@100yrds, which is consistent for other scopes of similar mag power and size. 25mm tube.
.
Click to expand...

Something definitely sounds strange here...don't think there's ever been a Bushnell scope with that much adjustment.....
 
Dmay said:
Something definitely sounds strange here...don't think there's ever been a Bushnell scope with that much adjustment.....
Click to expand...

Just had a lengthy conversation with one of the technicians at Bushnell. He confirmed that there is nothing wrong with my scope, and that having much more adjustment than what is advertised is not uncommon. He indicated that the rated adjustment that you see advertised is the IDEAL adjustment range, and Bushnell does not recommend adjusting a scope outside of that range as it can cause parallax issues, or damage to the scope mechanism if heavy recoil is applied to the scope while at the extreme ends of the adjustment range.
 
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