Am I understanding this correctly?

Nightcap

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Trying to understand the world of long range to expand my horizons. One thing I'm not sure I understand is how to be able to tell when you need a tapered mount. For example, according to this chart this projectile would drop 8.61 mils at 1,000 yards.

Assumption #1: a mechanically zeroed scope's POA would not match the POI at that range, but if you dialed the scope by X clicks to adjust by 8.61 mils, then the center point would then be aiming directly at the POI at 1,000 yards.

So if a scope advertises, say, 30 mils elevation adjustment meaning you could adjust by 15 mils downward, is that scope then capable of zeroing at 1,000 yards on a 0moa mount as 8.61 mils is within that 15 mil adjustment range?

Assumption #2: If a scope's internal adjustment range matches or exceeds the predicted drop of a projectile (such as the projectile that drops 8.61mils used with a scope with 15mils adjustment) you are perfectly fine with a zero taper mount. But if a round dropped (exaggerated) 30mils, and your scope only adjusted 10mils downward, you would then need a 20mil taper mount before the POA and POI would match?

I don't know if I'm explaining this question properly, but a lot of noob articles I've seen blankly state you "need a 20moa mount before you think about 1,000 yards" but then either omit info about the scope entirely or plug in an amazon link to a $100 scope.



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Skookum

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With a flat shooting cartridge, you may well be able to get to 1k yards w/o a tapered rail.

But your 1k setting would be at the very edge of the adjustment range.

There are some optical effects of being at the edge of the optics that I am unqualified to explain fully. Suffice to say, it is best to stay as close to optical center as possible.

This is where the tapered mount comes in, and it allows the shooter to use almost all of the scopes adjustment to get out to distance as well.
 
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Nightcap

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With a flat shooting cartridge, you may well be able to get to 1k yards w/o a tapered rail.

But your 1k setting would be at the very edge of the adjustment range.

There are some optical effects of being at the edge of the optics that I am unqualified to explain fully. Suffice to say, it is best to stay as close to optical center as possible.

This is where the tapered mount comes in, and it allows the shooter to use almost all of the scopes adjustment to get out to distance as well.
The example I'm using is based off 338 lapua with a nightforce 7-35x. If I wasn't going to dial in every shot, and wasn't going to shoot at a variety of ranges using a reticle with mil marks instead of a plain ol' crosshair, would adjusting that full 8.61mils even be necessary if one were to use the reticle to its potential? For example, only adjusting the scope 2.5 mils down to be zeroed at 500 yards but know the POI at 1,000 is X number of hash marks down from the center of the crosshair- would a taper mount be even less necessary then?

I guess a better version of my question is what specific numbers do you look for when you're shopping around for optics and calibers where you "know" if you need a taper mount or not
 

AIAW

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There is a very, very strong chance that your rifle has built-in rail declination. Mount declination is additive on top of this value. It’s typical stamped onto the rail itself, sometimes.

Do you see this on your rig?
 

plidenbrock

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That's actually an interesting question, if I understand what you're asking...

Several things jump out at me as important, so forgive me if you already know them:

Assuming that the zeroed scope at 100 yards is near its central adjustment on a 0 moa mount, then to get to 1,000 yards you would dial in the necessary elevation, in your example 8.6mils. On a scope with 30mils total internal travel, that would cause the reticle to now be 15 + 8.6 = 23.6mils. You would therefore have 6.4-ish mils of elevation remaining. That is, the front of the erector tube would be only 64 clicks from the bottom of the scope tube.

Were you to desire to zero at 1,000 yards, this would be its permanent position. Therefore to zero at 1,000 yards seems easily feasible in your example with a 0 moa mount.

I assume you understand that at ranges closer than that - should the need arise - being zeroed at 1,000 yards would require you to hold ABOVE the crosshair, NOT BELOW. The bullet would be leaving the barrel on a trajectory so far above the line of sight (PoA) that at 100 yards it would be almost 9 MILS above Point of Aim, which works out to 1000h=Dm: rearranging (100*9)/1000 = 0.9 yards or 32 inches or 2 feet 8 inches ABOVE point of aim at 100 yards!!

So in order to hit at 100 yards (in whatever scenario that might be) would require you to hold the crosshair UNDER the target by 9 mils.

If my understanding of the Nightforce reticles is correct, then that might be a problem because
1) the reticles don't go that high above the crosshair to begin with, and
2) there are no windage-hold marks up there in that part of the reticle anyway (although at 100 that might not matter), and
3) you would need to have your zero-stop set waaaaay below your true zero because you'd need to be able to under-dial 9 mils to come back to 100 yards poa=poi.

That's all not having mentioned the mountain of confounding factors you'd have to account for (windage variance, ammo temp / muzzle velocity variance, variable environmental conditions, scope / reticle cant, rifle cant, etc etc etc.) in your 1,000 yard zero which would be a giant headache.

WHEN you miss, it would be extremely difficult to know which of those factors accounted for the miss, and by how much.

Zeroing at 500 yards might be a better choice because then you can use the reticle UNDER the crosshair to hold for extra elevation to get you to 1,000 without having to hold off in space somewhere in the top of the reticle for any closer shots. And this would also be usable with a 0 moa incline: 15mil + 2.5mil = 17.5mil, which is close to the optical center of the lens set, which would minimize any optical aberrations from the periphery. A 500 yard zero is a better choice, and with the Nightforce reticles you'd only need that 2.5-ish mils ABOVE the crosshair for closer shots, which the reticles DO have. Plus, it would lessen the many confounding factors.

If you're considering Nightforce, then you probably don't need to worry too much about the accuracy of turret adjustment.

Zeroing at 100 yards would then be a MUCH better option because you can rule out most of the confounding factors mentioned above. As reliable as Nightforce turret adjustments are, dialing will not present a problem. And there is PLENTY of travel to get you to 1,000 yards from a 0 moa mount in the 7-35x. If you chose the Mil-XT, then EASILY you could hold without even having to dial to get you there. Then, it would be as you said, "using the reticle to its potential".

When I'm looking at scope elevation travel, the important things for me to consider are the accuracy / reliability of the scope turret input (not usually a problem with Nightforce), the maximum range I intend to shoot, and finally the maximum supersonic range of the cartridge. Then it tells me what I need. My current rifle du jour has integral scope mounts on a 0 moa incline, and yet there are plenty of scopes that can get me to the meager 1,400 yards supersonic limit of my cartridge. In my case, the tube and objective bell diameters are the biggest headaches.

HTH...that was an interesting question!
 

Yote Klr

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Zeroing at 500 yards might be a better choice because then you can use the reticle UNDER the crosshair to hold for extra elevation to get you to 1,000 without having to hold off in space somewhere in the top of the reticle for any closer shots. And this would also be usable with a 0 moa incline: 15mil + 2.5mil = 17.5mil, which is close to the optical center of the lens set, which would minimize any optical aberrations from the periphery. A 500 yard zero is a better choice, and with the Nightforce reticles you'd only need that 2.5-ish mils ABOVE the crosshair for closer shots, which the reticles DO have. Plus, it would lessen the many confounding factors
No. You'll still be seeing the image from the edge of the lense. Crosshair adjustment does nothing to center the scope.
The only way to center that image is elevate to rear of the scope.
 
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TacticalDillhole

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20 MOA is the standard. There are use cases for 30 and 40 MOA mounts as well. For long guns I never use less than 20 MOA for the reasons Skokie started. As for not dialing and using holds. I say good luck with that. It’s sounds cool but it isn’t practical. Distance gives you time and opportunity to dial. Not to mention that if you were going to hold for a 1k shot you wouldn’t be AB,e to read the numbers on the reticle because it would be on lower mag in order to see that low. If you dial, it doesn’t matter.
 
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Rerun7

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Don’t over think it. Zero your scope at 100 yards and see how much elevation you have in your scope. If it’s within the range you want to adjust to then you’re done. If you need more mils then get a base that offers enough slope to get you there.

FWIW I shoot .308 to 1k without issues. I have a 0 MOA base and dial 12.6 mils just fine with the scope.
 

chevy_man

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Don’t over think it. Zero your scope at 100 yards and see how much elevation you have in your scope. If it’s within the range you want to adjust to then you’re done. If you need more mils then get a base that offers enough slope to get you there.

FWIW I shoot .308 to 1k without issues. I have a 0 MOA base and dial 12.6 mils just fine with the scope.

This. Granted, my mark5 has a lot of elevation, but I can dial well past 1k with a flat base on my 6.5 creed.
 

lash

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@Nightcap, first I realize that you were using an exaggerated example above, but a 20 mil canted rail is not a thing. Maybe you meant that, but in case you didn’t, a typical rail of 20 moa is about 6 mils of cant.

Second, it is certainly possible to reach 1000 yards dialing a scope while using a 0 moa rail, but you better have the right scope and the right caliber to do so without issue. Just yesterday, and also very often other shooting days, there was a shooter with factory .308 ammo, a factory 20” barrel and a relatively inexpensive scope who realized that not only did he run out of dial adjustment, but also ran at the bottom of his reticle in order to reach the 1000 targets. He did not do very well as a result (one reason anyway) and was already asking if a 20 moa rail was enough or should he go 30 moa?

Third, since you are shooting .338, a mile capable cartridge, why would you limit yourself to 1000 yards just because you can? I rarely shoot my .338 under 1000 yards except for load development and sometimes for fun. Take that rifle out for a little ELR shooting and you’ll quickly find yourself kicking your stubbornness to properly outfit your scope mount.
 

Steel head

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@Nightcap, first I realize that you were using an exaggerated example above, but a 20 mil canted rail is not a thing. Maybe you meant that, but in case you didn’t, a typical rail of 20 moa is about 6 mils of cant.

Second, it is certainly possible to reach 1000 yards dialing a scope while using a 0 moa rail, but you better have the right scope and the right caliber to do so without issue. Just yesterday, and also very often other shooting days, there was a shooter with factory .308 ammo, a factory 20” barrel and a relatively inexpensive scope who realized that not only did he run out of dial adjustment, but also ran at the bottom of his reticle in order to reach the 1000 targets. He did not do very well as a result (one reason anyway) and was already asking if a 20 moa rail was enough or should he go 30 moa?

Third, since you are shooting .338, a mile capable cartridge, why would you limit yourself to 1000 yards just because you can? I rarely shoot my .338 under 1000 yards except for load development and sometimes for fun. Take that rifle out for a little ELR shooting and you’ll quickly find yourself kicking your stubbornness to properly outfit your scope mount.
This.
 
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Rerun7

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To me it seems like a waste to not use a tapered mount. I’d rather have the extra mils and not need them than to not have them at all.

Sure, if you want to cover all the bases and have money to burn then why not, it for sure won’t hurt.

For a new shooter trying to get into long range I always recommend to spend money on ammo and start shooting. Once you do that you can figure out what gear, accessories, changes you need to make.

Too many people want to just start at the end based on what other people tell them without putting in work to learn for themselves and then end up buying a bunch of stuff they really didn’t need or would have preferred to spend their money in another area.

The OP mentioned sites that told him he “needs” a 20 MOA base to reach 1k yards.

Until you get some rounds down range you aren’t going to know what you “need”
 

hlee

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If you have a scope and a rifle- but no mount- it makes no sense in 2019, to buy a 0 MOA mount when mounts with built in cant are readily available and are no more expensive. Future proof yourself and buy a mount with at least 20 MOA. There is, literally, no down side. In fact, buying a 0 MOA mount to learn that you need a 20 or 30 moa mount IS a downside.
 
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AIAW

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Sure, if you want to cover all the bases and have money to burn then why not, it for sure won’t hurt.

For a new shooter trying to get into long range I always recommend to spend money on ammo and start shooting. Once you do that you can figure out what gear, accessories, changes you need to make.

Too many people want to just start at the end based on what other people tell them without putting in work to learn for themselves and then end up buying a bunch of stuff they really didn’t need or would have preferred to spend their money in another area.

The OP mentioned sites that told him he “needs” a 20 MOA base to reach 1k yards.

Until you get some rounds down range you aren’t going to know what you “need”
Agree on some fronts, but this entire thread already derailed the normal "standards". The OP has a rifle chambered in 338LM. The term "new shooter" and "338LM" should never be used in the same sentence. Worst cartridge ever for a beginner, in multiple aspects.

If it's a factory rifle, it's going to have 20 or 30 MOA declination on the rail. It's just standard these days for long-range rigs. If it's a custom and someone built it without any declination then that's just poor customer service in my opinion. Perhaps this is a rifle that is "to be ordered" and the OP is curious on how to order - not sure there. A rail is so inexpensive in the grand scheme of things it's a no brainer to just install a 20 or 30 and call it done for the life of the rig. This entire thread exists because of a part that should be standard on any long-range rig. 20 rounds of ammo or a declined rail. No brainer. 338LM costs considerable money to feed.

We don't know the OP's skill level or if this is their only rifle. If just starting out, poor caliber choice. If seasoned at shorter ranges and good at fundamentals, let the 8.6x70 flow!
 

Precision Underground

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Sure, if you want to cover all the bases and have money to burn then why not, it for sure won’t hurt.

For a new shooter trying to get into long range I always recommend to spend money on ammo and start shooting. Once you do that you can figure out what gear, accessories, changes you need to make.

Too many people want to just start at the end based on what other people tell them without putting in work to learn for themselves and then end up buying a bunch of stuff they really didn’t need or would have preferred to spend their money in another area.

The OP mentioned sites that told him he “needs” a 20 MOA base to reach 1k yards.

Until you get some rounds down range you aren’t going to know what you “need”
I get what you are saying- but my point is why not just buy the canted base to start with? That makes more sense than buying a flat base and then buying a canted base later when you get bored with 1000 yards. If you already have a flat base don’t run out and buy a canted base because the internet told you. But if you need a base and you want to shoot long distances it makes no sense to buy a flat base and throw 1/2 of your mils out the window.
 
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Rerun7

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Don’t misunderstand me nothing wrong with having one or starting off with where you think you may go later given that it’s a .338.

I was specifically reacting to the OP saying that he had seen he “needed” one before even thinking about going to 1k and that’s not true.

But as AIAW mentioned, there are already a number of variables to address here beyond the base which I totally agree with.
 
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acudaowner

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you could use an adjustable rail and deside later if you want 20 dial 20 30 same thing think up to 150moa or more . or go flat and use turrets I have not tried the adjustable rails just scope and not to 1k or beyond yet .
 
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Precision Underground

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If you have a scope and a rifle- but no mount- it makes no sense in 2019, to buy a 0 MOA mount when mounts with built in cant are readily available and are no more expensive. Future proof yourself and buy a mount with at least 20 MOA. There is, literally, no down side. In fact, buying a 0 MOA mount to learn that you need a 20 or 30 moa mount IS a downside.
This. Exactly my point.
 
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david walter

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I’m still puzzled at why a person would buy multiple mounts with differing MOAs, instead of rings that can cover all that ground in one purshase?
 

IronmanDaremo

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My RPR came from the factory with a 20 MOA cant. I would have bought a canted mount otherwise before setting up the scope. Everything I read told me that would be the way to go if I even had an inkling to go up to and past 1000 yds. :shrugs:
 

Maxduty

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I'm' surprised no one has noticed the chart above assumes a 200 yard zero. More adjustment is already eaten up before dialing to 1K. Given that most scopes are already into the drop, it'll never make it. It's more than likely too far off center to begin with.