20 MOA Mount school

**wideglidejoe** · 04-02-2018, 11:35 PM

Jacko,

Thanks for the info, and for running those numbers! With that info, I won't rush to buy a 20 MOA mount. I've got 65 yr old eyes, they will probably be the limiting factor before the scope or mount. I've zero'd it at 200, the farthest I've shot it so far is 300. The 200 yd zero buys me a little more yds from what you quoted me above. If I could get to 800 yds on my abilities, I'd be tickled. I've always thought if I started shooting a lot farther on a regular basis, I'd probably move up on magnification too, but for now I'm OK with the 4X12, it kinda fell in my lap when I was looking for a scope, and it was "new in the box". This rifle is probably gonna be a 50% hunting rig and 50% paper/steel rig, so even if this scope and mount are good for 800 yrds, I can't imagine I would ethically pull the trigger on a critter past 400 yds.

KSwhitetail, I'll be watching for your update after the range trip!

Thanks again,
Joe

**bj139** · 04-03-2018, 12:02 AM

Is your mount mounted backwards?

**Kswhitetails** · 04-03-2018, 02:42 AM

No sir. Saw this earlier, forgot to answer you. Apologies.

**98Z** · 04-03-2018, 06:10 AM

There's a whole lot of math involved in this thread, and it's all math. Mount the scope, shoot the scope, start at 25 yards and get on paper. Stretch it after that, to your zero distance.

This is getting way more complicated than it needs to be... Shoot the Gun.

**Kswhitetails** · 04-03-2018, 02:09 PM

Originally posted by 98Z View Post

There's a whole lot of math involved in this thread, and it's all math. Mount the scope, shoot the scope, start at 25 yards and get on paper. Stretch it after that, to your zero distance.

This is getting way more complicated than it needs to be... Shoot the Gun.

Aye aye, cap. I’ve already posted earlier about how this is an accdemic discussion at this point because of the things you mention. I’m going Thursday noon to the range unless an interview rears it’s ugly head. Which I would be half greatful for. I plan on reporting back, but I will repeat the original intent. I want to learn, want to ensure I understand the math, the reasoning behind it, and to expand my brain somewhat. Others may feel the same sir.

**98Z** · 04-06-2018, 03:25 AM

Here's what happens, brother - if you had your scope mounted in a standard mount, and you didn't do anything in the world except mount that same scope, in the same location, but into a 20MOA mount, this is what happens...

Great article, from Warne Mounts...

20 MOA Explained

https://warnescopemounts.com/20moa-explained/

There are many misconceptions in the world about what a 20MOA base does. Many of those misconceptions stem from perceptions about what a 20MOA base is capable of providing, and when it is needed on a rifle. Many shooters who want to shoot long range automatically assume they need a 20MOA base, without fully understanding what the base does, or how it can affect their rifle and scope performance. The first piece to the puzzle is defining what “long range” is. We sometimes get customers who say they are shooting long range, when it turns out they are only shooting 200-300 yards. To some, this would be considered long range, to others it may be the starting point where their rifle will be zeroed. Truth be told, to define “long range” it will depend on the shooters perception of long range. For the purpose of this blog post, we will say long range is anything 600 yards and beyond. Since many rifle, cartridge and scope combinations start to reach their limit with a 0MOA base around this range. Your particular combination may differ, but this is a generalization to explain what a 20MOA base does. Why would anyone need a 20MOA base? A 20MOA base is only needed for certain applications. When a shooter is adjusting the elevation dial on the scope for ranges longer than what the gun is zeroed for, at some point, they will run out of elevation in the scope. In many instances this is around 600 yards, give or take. For example, if a shooter had a scope with 40MOA of total elevation travel, and the rifle was zeroed at 100 yards in the center of that travel, they would have 20MOA worth of adjustment both up and down. When the rifle is zeroed in the center of the scope travel, there is 20MOA worth of down adjustment that will never be used. In its most basic form, a 20MOA base allows you to use that extra 20MOA of travel in the scope that was not being used. So in this case, if the shooter had a 20MOA base, the rifle would be zeroed at the end of its elevation travel, and the shooter would have 40MOA of elevation at their disposal, allowing them to shoot longerdistances. How does a 20MOA base work? A 0MOA base is considered flat, or level with the bore of the gun. A 20MOA base is canted down in the front toward the barrel. By canting the base down in the front, this is what allows for more usable elevation adjustment in the scope. To many shooters who are not familiar with the concept, canting a scope down in front sounds incorrect. They feel it makes more sense to them if the scope is pointed up. To help explain how this works, please take a look at the illustration below. If we had a rifle with a 0MOA base, and there was a laser going through the middle of the scope, and the middle of the rifle bore that went forever, and lets say the rifle was zeroed at 100 yards, those 2 lasers would intersect at that 100 yard target. If we then changed to a 20MOA base, the scopes laser would be on target, and the rifles laser would be hitting the target 20 inches high. This is essentially how a 20MOA base works, since you are now hitting 20 inches high, you can dial the scope back so the rifle is zeroed at 100 yards again, and you have an extra 20 inches of elevation to work with. A 20MOA base is not always the best base to use, depending on the rifle and its purpose. In some cases, the scope being used when being paired with a flat shooting cartridge, cannot dial the added 20MOA of elevation out to keep the gun zeroed at 100 yards. The rifle must then be zeroed to 200 or 300 yards. This will entirely depend on the combination of rifle, scope and cartridge, so it is important to know how much MOA of elevation travel a scope has when deciding whether or not to purchase a 20MOA base. In situations where a ballistic compensating reticle is being used for long range shooting, a 20MOA base may not be needed, because the shooter is not adjusting the elevation dial. Since the elevation is not being changed on the scope, a 20MOA base would serve no purpose. In 2015, Warne was able to extend the scope of 20MOA capabilities beyond picatinny rails with the introduction of the LRSKEL Mount. Utilizing state of the art technology, Warne is able to cut a 20MOA cant into the scope bed of the mount. This allows for a 20MOA mount while retaining all of the same dimensions and characteristics of the popular X-SKEL mount. Warne is expanding the possibilities of modern sporting rifles by offering a sleek, rugged, one piece mount with the rock solid reputation of the RAMP and X-SKEL, while targeting long range precision shooters. Read more about the LRSKEL mount Here. In the current state of long range shooting, competition, and hunting, a 20MOA scope mount may be just the ticket for your rifle. Warne offers an extensive line of 20MOA picatinny rails for many popular rifle platforms. If you prefer a flattop AR platform rifle, the LRSKEL is an excellent choice to extend your range. If you are in the market for a solid, precise, American made 20MOA mount for your long range rifle,Warne Scope Mounts is your first and last stop forgoing the distance, and making every shot count.

**98Z** · 04-06-2018, 03:55 AM

Originally posted by wideglidejoe View Post

I'm using the Leupold Mark AR Mod 1 4-12X40 SKU#115392. Specs on Leupold website show 67 MOA elevation, so from reading comments above, I'd wind up with 67/2=33.5-20=13.5 & 53.5?

I'm running a Leupold Mark AR Mod 1, 1.5-4 Firedot, with the similar specs of drop (125 MOA total travel) in a Nikon M223XR mount, with 20 MOA built into the mount - on the 12.5" Grendel.

That scope was directly taken off a 16" 300BLK gun, and it was zero'd for that gun. Man, was it an initial bitch to zero, after just slapping it in the new 12.5" shorty - in the 20 MOA mount. I was high over target like a mofo. It was almost an entire elevation wheel to get it down, on paper.

That 12.5" Grendel floored me. That gun shocked me. Bad. The 18" Gren went 3.3 mils to 500 yards, and 8.2 mils at 845 yards,on steel. So, I knew the short one would get to 500. Man, did it ever. the 12.5" went 4.1 mils at 500, and 10.2 mils at 845 yards. Repeatedly, accurately. It hit steel better at 845 than either of the Mk12 Mod 0 and Mk12 Mod 1 builds, shooting 75gr Hornady BTHPs that are worked up for those guns.

For a measuring stick, the Rem 700 AAC-SD in .308 gets to the 845 at 9.0 mils of drop, with a hand load of 178gr Hornady BTHP. The 18" Gren smoked it, and the 12.5" Gren wasn't far behind, in drop to target.

There's more coming up, on that load. It was hot - Very. I've cut that down now, and hit a node a full grain lower than what that stuff was loaded at - and I need to rework all my data at distance. Basically, it was 2585fps out of the 18" Gren, and 2370 fps from the 12.5" Gren, same load running Hornady 123gr ELD-M projectiles. Flatass primers, no cratering, but serious ejector swipes. It was right on the edge.

I have the new load, and node, and I'll work with it, and get better numbers up once I get it all together. Accurate 2520 is the powder.

**98Z** · 04-06-2018, 04:11 AM

So, with all my data being in mils, think about this...

Between 500 yards and 845 yards, I was (on the 12.5" gun) 4.1 mils, and 10.2 mils, respectively, for those two distances. Fuk, was that load hot, though.

Mils to MOA is a simple multiplication. There are 3.4377 MOA per Mil. I was 4.1 mils (14.09 MOA) at 500 yards, and 10.2 mils (35.06 MOA) at 845 yards.

Does your scope have 35 MOA of drop, if you want to shoot at 845 yards, with your 12.5" Grendel?... (with my hotass load... - eff that load...) If it does, inherent in your scope travel, you don't need a 20 MOA mount. If it can't make that drop, in your inherent scope travel, and that's your distance you need to hit - then you need a drop-mount...

**Zeus** · 04-06-2018, 04:35 AM

Originally posted by bj139 View Post

If you can't get a good boresight at 25 yards you are not going to git er done.
For a 100 yard sight in you should hit about the scope height low at 25 yards.

BJ is right you need to be low.....If you're 4" high at 25 yards then you won't even be on a standard sized sheet of paper at 100 yards.......98Z has a good point too.....the only way to tell for sure is to go and shoot the rifle and see where it ends up. I just sighted in a 6mmAR 1.5" low at 25 yards with a 20 MOA base installed and had plenty of elevation adjustment in my 36X Sightron and it only has 60" of total elevation adjustment.

**98Z** · 04-06-2018, 04:54 AM

Read the article I linked, guys, and think about MOA. 1 is at 100 (1.047" at 100 yards, to get really into it...). It would be 2 at 50. 4 at 25. Same width. Can't argue that.

Look at the Warne article, and dispel the myths. Really run the math.

"If we had a rifle with a 0MOA base, and there was a laser going through the middle of the scope, and the middle of the rifle bore that went forever, and lets say the rifle was zeroed at 100 yards, those 2 lasers would intersect at that 100 yard target. If we then changed to a 20MOA base, the scopes laser would be on target, and the rifles laser would be hitting the target 20 inches high. "

20 inches high at 100 is what, at 25 yards? Divide by 4. It's 5" high at 25 yards. You just went to 4" high, at 25 - you just proved that you have enough internal scope travel...

Read the article I linked, guys. Quit trying to math this all out, and just go shoot the gun. It will work. The scope will magically zero, at whatever distance you are trying, in a 20 MOA mount, and all with be right in the world.

**98Z** · 04-06-2018, 05:50 AM

You guys are all trying to run some kind of Nerd Math on all this, and the Nerd Math isn't going to work out. I'm going to tell you that I have the Nerd Magic within me, and it's going to work...

You can believe me, or not. You need to shoot the gun, or talk about shooting the gun...

**98Z** · 04-06-2018, 06:10 AM

Originally posted by bj139 View Post

If you can't get a good boresight at 25 yards you are not going to git er done.
For a 100 yard sight in you should hit about the scope height low at 25 yards.

For what it's worth, that's in IMPACT. That's for trying to Zero a scope at 25 yards shooting distance, and trying to equate that to a 100 yard zero-ish impact. 100 yard zero will IMPACT low at 25 yards, and if you'd know that impact distance, at 25 yards, you could math it all out for 100.

Here's an example - my "way too hot" 12.5" load is 1.3 inches low at 25 yards, for a 100 yard zero.

can't argue the ballistics or the math, when the numbers were put in for my adjustments at 500 yards and 845 yards (850 yards on the chart)...

The load really did THIS...

12-5 way too hot.png

20 MOA Mount school

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