Rifle Scopes Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

[2500yards]

Why could this be happening? I am maxed out on elevation on a 50 yard shot?

This is on an AR-15.

I dont know if Im just a huge idiot and not doing something correctly here. but I just bought the burris PEPR mount for my new Nightforce 12-42X scope. I mounted it up and went to sight it in at 100 yards. I shot 2 shots on a fresh target without anything hitting the 20 X 16 inch target at all. I moved up to 50 yards and shot 2 times with the impacts on the very bottom of the paper. I moved my elevation up on my scope all the way, which just put me in the target.

what can I do?

 

[match308]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

Are you positive you're not turning the elevation down? That'd be about where you'd hit if you cranked it down all the way.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

Im turning it the way the scope says to. Am I wrong?

Which way would you turn this?

 

[KYS]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

you would be turning counter clockwise to move up.
The closer you get to your target your shots will move down.

 

[cinosbus]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

Check to make sure that the mount is on all the way and on correctly, so that it's not tilting the scope downward.

The PEPR isn't a 20moa or something is it?

And turn it counter-clockwise to raise the point of impact.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

I just took it all part and checked everything. no issue at all. Im just saying screw it and shimming the rear side. I need to shoot tomorrow. but it really has me confused as to what is causing the problem.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

I just went out and took some video and pics with my cellphone. I just want to be clear. At 100 yards, with the elevation all the way up "Counter Clockwise" I am just getting on target. If I move the elevation down, the impact is lower.

 

[Trigger Monkey]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

If your scope is the NXS 12-42X56 then it only has 45MOA of total internal travel, if you cut that in half the scope will have about 22.5 MOA in each direction if it is centered within the tube. If you're using a mount with zero taper on a flat top AR then it is possible to run out of elevation by the time you get zeroed. The remedy is to get a base or riser that has some amount of taper to it.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Trigger Monkey</div><div class="ubbcode-body">If your scope is the NXS 12-42X56 then it only has 45MOA of total internal travel, if you cut that in half the scope will have about 22.5 MOA in each direction if it is centered within the tube. If you're using a mount with zero taper on a flat top AR then it is possible to run out of elevation by the time you get zeroed. The remedy is to get a base or riser that has some amount of taper to it.
</div></div>

It is the NXS 12-42X56. Just doesnt make sense that a flat top would cause that much of an issue. I have had a couple of other scopes on this rifle without any kind of issue like this.

 

[NET65]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

Thats a lot of glass for an Ar-15!

 

[Trigger Monkey]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

It makes a lot of sense when you think about it. The sight height of that system is in the neighborhood of 2.5" or so. With no taper on that mount that scope has to make up for the sight height from what elevation is left above center. It's the amount of elevation above center that gives you the ability to dial out to longer distances. Combine that with a scope that has a limited amount of elevation to begin with due to the high magnification and it can quickly eat up the amount of travel available in the scope. This is just a case of having an improper rifle/mount/optic combination.

 

[savage110]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

trade it for a 3.5x15 and see the difference! that way you wont have overkill of a scope on your AR either....

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The new guy</div><div class="ubbcode-body">Thats a lot of glass for an Ar-15!</div></div>

yeah, just a tad..

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Savage110</div><div class="ubbcode-body">trade it for a 3.5x15 and see the difference! that way you wont have overkill of a scope on your AR either....</div></div>

I dont intend to use it only on my ar-15. I am shooting at 1000 yards with it and wanted more magnification.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Trigger Monkey</div><div class="ubbcode-body">It makes a lot of sense when you think about it. The sight height of that system is in the neighborhood of 2.5" or so. With no taper on that mount that scope has to make up for the sight height from what elevation is left above center. It's the amount of elevation above center that gives you the ability to dial out to longer distances. Combine that with a scope that has a limited amount of elevation to begin with due to the high magnification and it can quickly eat up the amount of travel available in the scope. This is just a case of having an improper rifle/mount/optic combination. </div></div>

That doesnt make sense to me at all. please explain to me how to height of the scope would effect the angle of the shot? I've had higher scope mounts and lower scope mounts and never had something this drastic happen?

 

[Trigger Monkey]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

Ok...take a look at this Sloped Bases and Rings

In the article it explains what goes on inside of a riflescope that is sitting on a sloped base in order to get zeroed.

With a flat top rifle and a scope that is optically/mechanically centered the centerline of the scope and the centerline of the bore are parallel. So when you are looking at a target, you and the scope may be looking at the bullseye but the centerline of the bore that is hanging a few inches below it is actually looking at the bottom of the target. To intersect with the bore you have to dial in more elevation because inside of a riflescope, the image that the reticle "sees" is inverted so that when you turn the knob CCW to dial in more elevation it looks like the reticle is moving downwards to intersect the point the muzzle is looking at. This is what eats up the amount elevation that is available to you. Some scopes have enough elevation to do this and still have plenty left over to reach out hundreds of yards.

 

[KClark]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

Can you post a pic of the drivers side of scope please.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Trigger Monkey</div><div class="ubbcode-body">Ok...take a look at this Sloped Bases and Rings

In the article it explains what goes on inside of a riflescope that is sitting on a sloped base in order to get zeroed.

With a flat top rifle and a scope that is optically/mechanically centered the centerline of the scope and the centerline of the bore are parallel. So when you are looking at a target, you and the scope may be looking at the bullseye but the centerline of the bore that is hanging a few inches below it is actually looking at the bottom of the target. To intersect with the bore you have to dial in more elevation because inside of a riflescope, the image that the reticle "sees" is inverted so that when you turn the knob CCW to dial in more elevation it looks like the reticle is moving downwards to intersect the point the muzzle is looking at. This is what eats up the amount elevation that is available to you. Some scopes have enough elevation to do this and still have plenty left over to reach out hundreds of yards. </div></div>

Thanks for the link. I understand how that all works. Its just that in the case of my scope/mount it is acting as if I have a 40 MOA negative elevation mount. There has to be something wrong with the mount.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KClark</div><div class="ubbcode-body">Can you post a pic of the drivers side of scope please.</div></div>

I didnt take anything other than what you see. Is there something that you would see that could help?

 

[Trigger Monkey]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

I would almost guarantee you there is nothing wrong with the mount. So far it sounds like its acting like a 0 MOA mount with a scope that only has about 45 MOA of total travel. If you were using a different optic that had something on the order of 100 MOA or so of total internal travel then the whole thing would be a none issue.

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

Why on earth would they make a scope for extreme long range shooting, that would need to use all MOA elevation just to hit a target at 50 or 100 yards? Its not like a 50 cal is going to be 50 MOA higher at 50 yards then a 223..

I will have to contact nightforce about this one. This just doesnt make sense.

 

[matchking]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2500yards</div><div class="ubbcode-body">Why on earth would they make a scope for extreme long range shooting, that would need to use all MOA elevation just to hit a target at 50 or 100 yards? </div></div>

If anyone is doing "extreme long range shooting" with that model, they don't also shoot close-, mid-, and long-range with it. The 12-42x, as well as many other high power scopes, don't have the adjustment range to be effectively used over a wide distance range. While I have a few high-powered scopes, I tend to like ones with alot more adjustment built it. It makes life easier.

The issue you are having has been explained pretty well in the posts above by TM.

 

[KClark]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

Possibly, just a vague notion....

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2500yards</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KClark</div><div class="ubbcode-body">Can you post a pic of the drivers side of scope please.</div></div>

I didnt take anything other than what you see. Is there something that you would see that could help? </div></div>

 

[2500yards]

Re: Burris PEPR mount w/ Nightforce BIG elev. PRO

I will contact nightforce and discuss this with them. If the scope is causing this problem, then I dont want it. I appreciate your help Trigger Monkey. Its just that something doesnt seem right here. I've never had a scope over 15X, and the thought of spending alot of money, I wanted all the magnifacation I could get. If it turns out that is the issue, I hope they will replace it with a 22X or something.

 

[r0ttie1]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2500yards</div><div class="ubbcode-body">Why could this be happening? I am maxed out on elevation on a 50 yard shot?

This is on an AR-15.

I dont know if Im just a huge idiot and not doing something correctly here. but I just bought the burris PEPR mount for my new Nightforce 12-42X scope. I mounted it up and went to sight it in at 100 yards. I shot 2 shots on a fresh target without anything hitting the 20 X 16 inch target at all. I moved up to 50 yards and shot 2 times with the impacts on the very bottom of the paper. I moved my elevation up on my scope all the way, which just put me in the target.

what can I do? </div></div>

I had the same issues with a 8-32x56 on a bolt gun. I got a 20moa rail and the problem was solved.

 

[cinosbus]

Re: Burris PEPR mount w/ Nightforce BIG elev. PROBLEM

Sounds like you need a new PEPR or something is wrong with the scope.

If it was a 20moa base or something, you'd have a hard time getting LOW ENOUGH on the target, not have trouble getting high enough.

The bore to scope centerline is only about 2.5 inches on an AR, so all you have to adjust is about 2.5MOA to fix that, so that's not likely to be it.

Something is not lined up, machined incorrectly, or out of whack somehow.

My vote is the mount. Make sure your front picatinny clamp is in the cross slot on your flat top.

In looking closely at the picture, it looks like the front of your mount could be hitting the top of the flat top and pushing it up?

Something is angling the scope up at the front...