Rifle Scopes How much scope base cant/elevation do you use? 0MOA? 20MOA? 45MOA?

[Coloradocop]

I just set up my new AIAX 260, and went with a flat Spuhr mount on top of the 20moa rail that is built into the rifle. I figured that this would probably be about the ideal amount of extra elevation for this rifle. Though I haven't had a chance to proof it yet, the dope charts on JBM would suggest that I could get well beyond the supersonic range of this rifle with my S&B scope, when combined with the built in 20 MOA of extra elevation. I can tell you that I'm able to dial 23.4 Mils up from my 100 yard zero as I'm currently setup.

Lately I seem to be reading a lot of suggestions for going with a 45 MOA base, or something closer to that range. I figured doing that might prevent me from obtaining a 100 yard zero, or at least push it darn close on that end.

So, I'm just curious to hear what all of you are running, and why?

 

[10fp]

on 260 you can go 28-40moa.

40moa is the new 20

 

[Early Cuyler]

I have a S&B 5-25x56 in a Spuhr 44.4moa canted mount on top of my DTA. No issues with a 100yd zero and I have 64-65moa (two knob turns) to dial to. You shouldn't have any issue with a 260 and 100yd zero if you get a 20-25moa mount on top of the 20moa rail.

The primary reason I've done this is I will ultimately get a conversion for my DTA to use at a mile+ (338 variant of some sort I'd imagine). The 44.4moa base/mount will give me the most elevation options if/when I go that route.

 

[FatherMorpheus]

Wouldn't it really depend on the ranges you want to shoot at. If you are planning to always shoot out past 1000 yards with this rifle put a 30MOA or 40MOA type riser on the rifle. If you will only be doing that rarely, stick with the 20MOA.

Of course, you could always just sight in at 300 yards and know your hold-under for 200 and 100 yards. With that round, their shouldn't be too much difference.

 

[RHunter]

If you use the Nightforce 5.5x22 or the 8x32 then a 30 MOA rail is ideal. I like the reticle to be as close to the center of the optic after doping the scope when I'm shooting ELR. This gives me the best clarity from the optic. When the reticle is close to the edge you can get some distortion.

You need to look at the adjustment range the scope has that you want buy and divide it by 2. If 1/2 of the adjustment range is less than 40 then you need to use a 20 MOA rail, If 1/2 of the adjustment range is more than 40 then you should use a 30 MOA rail.

If your scope has 80 MOA of travel (40 up and 40 down) like the NXS 8x32 has, divide the 80 by 2 equals 40, add 30 back due to the slope of the rail, you will have a total possible 70 MOA of elevation adjustment. 30 MOA + or - of elevation at 1000 yards puts the reticle in the center of the optic where you have the best optical clarity.

 

[Coloradocop]

Hmmm... I guess maybe I should have gone with more cant. The shop was recommending a flat mount on the 20 MOA base, and I just went with their recommendation (knowing that this was also what I ran on my .308).

The dope chart for the factory load I was running suggests that I should be able to get to around a mile before I run out of elevation as things currently sit, but I'll be at the extreme end of the adjustment range at that point. I don't really know how many folks are using the .260 as a 1-mile gun (it would be subsonic by that point), but I figure that it probably runs out of steam before that point. Still, the idea of working more in the middle of the scope's adjustment range does make sense.

 

[10fp]

your fine, but if you can swap it for another 10-20 moa i would

 

[zac_c]

I have always used 20 moa but now I have a 45 moa and love it you get the most out of your scope.

 

[ProCharger]

I went with a 20moa, pretty easy decision for me though. I am shooting a .308 out of a 20". At 1000 yards (about the max I can reach) I need about 12 mils elevation according to the calculator. I wanted to keep my reticle as centered as I could and the 20moa is about dead on. I have 36mil of adjustment in my scope, I am 6mils below my optics center point with a 100 yard zero. At 1000 I am roughly 6 mil above optic center. Most of my shooting is in between so for me it all worked out perfectly. At 700 yards I need 6.15 mil elevation which is pretty much centering the reticle in the optic.

One thing you might want to check though is if you do intend to push the distance and plan on dialing wind instead of holds if you have enough windage left in your scope when near the top of your elevation. Not all scopes lose elevation but some do. My scope has a full 18 mils each direction when at max elevation but I have heard people say they lose windage when near or at max elevation.

 

[JAGERSPEAR]

I use a 25moa GDI with a F1 and have 78 moa after 100 zero. I'm about 3.5" above barrel. Could have went higher, but with 78 minutes - that will do just fine.

 

[RHunter]

I have always used 20 moa but now I have a 45 moa and love it you get the most out of your scope.

If you have less than 90 MOA of total adjustment you will never be able to zero at 100 yards with a 45 MOA rail in a 260.

Without knowing what the total adjustment range of the scope you will be using- this "I have a 45 moa base and I love it" is bad advice because you do not know what optic that is being used on. You are leaving out some pretty key info there.

It is critical you know what the adjustment range of the scope is that you want to use and you can not use a rail with a cant that is greater than 1/2 of the adjustment range of the optic or you will NEVER have a 100 yard zero.

I need about 12 mils elevation according to the calculator. I wanted to keep my reticle as centered as I could and the 20moa is about dead on.

That is completely Impossible. 12 Mils is 41 and 1/4 MOA so in order to be close to the center of your reticle at 1000 yards you would need a 40 MOA cant in your rail. If you are going 40 up, you need to be able to point the scope 40 down first and zero at that point.

POTENTIAL problem with this is, if you have 90 MOA of total adjustment, at 100 yards you will be looking through the edge of the optic and will not have target clarity unless you have some $3500 Schmidt and Bender. Nightforce scopes are good but when you are looking at the extreme bottom or top of the adjustment scale you do get some distortion compared to the top of the line glass.

If you guys don't know what the hell you are talking about, don't give any advice to pad your comment count. This is how new LR shooters get their heads filled with Bullshit and end up spending good money only to discover the BS they got from some forum was exactly that-- Bullshit!

 

[jonthomps]

I use a 20 moa. I think it's the perfect combo of giving me a little extra elevation in my scope but not sloping my scope so much that I need a higher mount. Crazy logic, I know.

 

[KWilson]

My March 5-40x56 is sitting on a 20MOA rail. The scope itself is mounted in an Era-Tac adjustable inclination mount which is adjustable in 10MOA increments and runs from 0MOA to 70MOA. She's set to 0MOA at present.

 

[timelinex]

You generally never need anything above 20moa mount unless your doing the really long range shooting. For example, with my 30moa mount, I can reach out to like 2100 yards with my 338...so when I was shooting 2300,i had to use holdovers... Next time I will get a 40.

However 99.9‰ of people won't be shooting past a mile (or the equivalent for the specific caliber), so it's not needed.

 

[Lowlight]

If you have no clue what you are doing, and just how far you can reach with 23Mils, why do you think you'll be effective at 1 mile.

1. Your scope has 23 mils of useable adjustment which is huge.
2. With a 140 going 2850 you can reach 1800 yards with 24 mils.
3. Your bullet is gonna be sub sonic that happens just before 1700
4. The wind in CO is gonna kick a 6.5s ass at that distance even here

there is no reason to change your mount. End of discussion.

Just because use you think you can doesn't mean you should, and if you don't know you can, or what means, or what your equipment is capable of, maybe you shouldn't.

 

[LawnMM]

I just set up my new AIAX 260, and went with a flat Spuhr mount on top of the 20moa rail that is built into the rifle. I figured that this would probably be about the ideal amount of extra elevation for this rifle. Though I haven't had a chance to proof it yet, the dope charts on JBM would suggest that I could get well beyond the supersonic range of this rifle with my S&B scope, when combined with the built in 20 MOA of extra elevation. I can tell you that I'm able to dial 23.4 Mils up from my 100 yard zero as I'm currently setup.

Lately I seem to be reading a lot of suggestions for going with a 45 MOA base, or something closer to that range. I figured doing that might prevent me from obtaining a 100 yard zero, or at least push it darn close on that end.

So, I'm just curious to hear what all of you are running, and why?

20 is fine. Ask yourself about what caliber you have and the intended targets to engage. 20moa on a 260 you will use for fun and competitions that might throw an occasional 1200yd target at you is quite sufficient.

You don't need a 40 mom base or maximum scope travel until you start talking ELR calibers and distances. My 308 is supersonic to close to a mile in Colorado but it's not a mile gun.

They gave you the right advice at the shop.

 

[RobertB]

I stick with 20MOA bases and have no regrets especially on SA rounds. On a long action ELR rifle I would give a 30 MOA or so base a consideration. Just know what your ultimate range will be, know the limits your cartridge has and go from there. You will see that with most decent scopes that 20 is just fine.Yeah, I have 35ish MOA wasted on some of my rifles but I have 60+MOA left and that will get you a ways, And I could have a scope with more adjustment. I can get out to a mile with my 260 with a 20MOA (Surgeon M591) So that's farther than the round is good for.

 

[ProCharger]

I need about 12 mils elevation according to the calculator. I wanted to keep my reticle as centered as I could and the 20moa is about dead on.



That is completely Impossible. 12 Mils is 41 and 1/4 MOA so in order to be close to the center of your reticle at 1000 yards you would need a 40 MOA cant in your rail. If you are going 40 up, you need to be able to point the scope 40 down first and zero at that point.

I thought I laid it out pretty well. From 100 yards to 1000 yards I have to use 12 mil elevation (actually 11.96 but we can round for the example). I have a Vortex Razor HD with 36 mils available travel. Once I zero at 100 I have 24 mils available so dialing 6 mils in elevation from 100 should be my reticles center. so I am 6 mil below optic center at 100, and 6 mil above optic center at 1000. Like I said before, I do most of my shooting in between, so I am about as close to the optics center for most shots. I never once said I had the reticle centered at 1000, in fact I said I have the reticle centered at 700 (6.15 mil elevation) but you chose to disregard that sentence.

I hope that clears up what I said but if I am in fact incorrect please PM me and explain. I am always up for learning.

 

[Coloradocop]

If you have no clue what you are doing, and just how far you can reach with 23Mils, why do you think you'll be effective at 1 mile.

1. Your scope has 23 mils of useable adjustment which is huge.
2. With a 140 going 2850 you can reach 1800 yards with 24 mils.
3. Your bullet is gonna be sub sonic that happens just before 1700
4. The wind in CO is gonna kick a 6.5s ass at that distance even here

there is no reason to change your mount. End of discussion.

Just because use you think you can doesn't mean you should, and if you don't know you can, or what means, or what your equipment is capable of, maybe you shouldn't.

I do get (and understand) some of what you're saying there, particularly when it comes to the scope travel range and ballistic math. I certainly do realize how far 23 mils will reach on the basis of the estimated muzzle velocities I'm expecting for this rifle, and that range is well beyond what I'd think would be considered a reasonable/optimal range for this rifle. I've personally never considered the .260 to be a 1-mile caliber, but I'm thinking that some people might be thinking that way with the 45 MOA base recommendations that seem to have become the norm.

I'm mostly just trying to figure out why many of the guys I'm shooting with (including some guys I know you shoot with) have traded up to 45 MOA mounts from 20 MOA mounts for rifles that are either chambered in .260 Rem, or ballistic equivalents within the 6.5 range. I'm wondering what I'm missing here, basically.

I've not shot this particular rifle enough to know where I'd draw my limits with it, and I've yet to put a round over a chronograph with it. It really is a new rifle, and I've got a lot of work to do with it still. Even with the somewhat slower "paper" numbers I crunched (derived from info on a factory match load), I should be able to get to 1300 yards on the first turn of my scope, and would be subsonic long before I ran out of travel in the scope.

So, to make a long story short, and maybe rephrase my own question a bit, where's the 45 MOA advantage everyone is talking about in the 6.5's? Or is this more of an Internet-driven trend?

I'll freely admit that for everything I've ever learned about this activity I've probably learned of 2 things I don't know. As such, I try not to dismiss any apparently popular recommendations without some research into why people may be trending in this direction. I would be inclined to believe the 20 MOA base should do everything I'd intend to do with the .260 Rem. But to put things simply: you often don't know what you don't know, until you know it. As such, please consider this thread an anal-retentive quest for knowledge on my part

(For clarity sake: I intend to shoot a lot between 500-1200 yards, and on occasion out to maybe 1,400-1,500 yards when I want to stretch it and have the real estate available to do so).

 

[RHunter]

My 308 is supersonic to close to a mile in Colorado but it's not a mile gun.

I'd like to see that load data because that statement made my BS meter go a bit richter... I can't say that I have EVER seen a 308 load that can stay supersonic close to a mile unless you are considering 1000 yards is close to a mile.

I thought I laid it out pretty well. From 100 yards to 1000 yards I have to use 12 mil elevation (actually 11.96 but we can round for the example).

Actually you didn't, those first two sentences are pretty misleading. I usually stop reading a post when the first two lines clearly make no sense.

I went with a 20moa, pretty easy decision for me though. I am shooting a .308 out of a 20". At 1000 yards (about the max I can reach) I need about 12 mils elevation according to the calculator. I wanted to keep my reticle as centered as I could and the 20moa is about dead on.

 

[6.5 GUY]

RHunter- I asked this very question to Jerry R. but never got an answer,

I have a 4-16x50 PMII/P 1/10 Mrad scope on order from Midway USA, I heard a few weeks ago I now wont see it until June 15th, 2014. But I would like to know what slope base angle should be used so I can have a 100 yard zero and maximum elevation range within the scope. I read a review that the AI AW Rifle used this scope with a 29 MOA base, but wondered since it has only 0-13 Mrad of elevation range would that be too much slope and still have a 100 yard zero without being at the very bottom of the scope adjustment range so it still very clear?

I was talking it over with Cameron Murphy of Murphy Precision, he can make them with any slope required. Since they are custom made out of titanium bar stock I need to get this as precise as possible, at $190.00 each it gets expensive for redoes! So with that said what slope angle would work the best? The scope will either be used on a Jarrett 280 AI and a GAP 6.5 x 47 Lapua.

Thanks for your assistance.

 

[Lowlight]

A 4-16x should be put on a 30MOA Base to get all of the elevation.

I did an online training video with 2 S&B 4-16s and 2 SPUHR mounts to show the difference. The 4-16x was designed around the 28MOA AI Mount, so for us here, a 30MOA base works perfect.

I spoke to Andy who was an Engineer @ S&B and was mostly responsible for the 5-25x at SHOT last week. He started Optronika which is now GSO. I specifically asked him about the 5-25x and he said with a 45MOA you have a much better erector position than with a 20MOA as people were saying there was too much angle in the erector with a 45MOA cant. He said to me the opposite was in fact true. Now, I am not a scope engineer, but if the designer of the Optic said to use a 45MOA cant to get 100% of the travel, then I would take that to the bank. However, there is a caveat... if you don't need it, and you have a 20MOA already and it gets you 23MILS of elevation. (which exceeds your max effective range of the rifle) why switch ? Unless you are independently wealthy of course.

The S&B were designed around the AI scope mounts, or vice versa as those two paired together many years ago... the 18MOA was for the 3-12x, the 28MOA was for the 4-16x and the 45MOA for the 5-25x... that should help guide you.

But for a 4-16x, get a 30MOA base and it's all good. The actual inside is close to 33MOA so you have 3 MOA left over.

 

[RHunter]

If you have 13 mrad of elevation, then you should have a total of 26 (13 up and 13 down) 13 Mrad rounded nicely is basically 45 MOA so you will most likely have 45 MOA up, and 45 MOA down. Since you do not want to be looking on the edge of the glass for a 100 yard zero, I would stay up at least 15 MOA so that leaves you with 30 MOA before you are at the center of the optic. I would get a 30 MOA rail and this will give you a total of 75 MOA of elevation, or in your case about 20 Mrad.

Most guns that can shoot to 1000 yards are around 20 to 40 MOA in elevation adjustment at 1000 yards.... I think the 6.5 x 47 Lapua averages about 7 mils so that is about 24 MOA... you will be sighting just below the center of the lens with a 30 MOA base at 1000 yards with the 6.5 x 47 and you will have damn near the best clarity your scope can deliver. If you shoot heavy bullets and lighter loads you will probably be in the center of the scope to compensate for the extra drop.

I don't think the 280 is much different but I am having a bit of a brain fart and I can not remember what the average is for a 280 but is is really fucking close to the 6.5 lapua.

I would not waste your money on a titanium rail, it is overkill x 10... Sounds cool, neat thing to brag to your friends about, but seriously overkill. Put the extra cash into ammo.

So to answer your question, a 30 MOA rail would be perfect for that scope on a 6.5 x 47 if you are planning to do 1000 yard work. If you do not plan to shoot much at 1000 then drop it down to a 20MOA base which would be ideal for the 500 to 700 yard range.

 

[RHunter]

Looks like Frank beat me to it while I was typing....

 

[LawnMM]

I'd like to see that load data because that statement made my BS meter go a bit richter... I can't say that I have EVER seen a 308 load that can stay supersonic close to a mile unless you are considering 1000 yards is close to a mile.

Okay, run your ballistics calculator for a 208 amax doing 2550 at 6000DA. I openly admit I don't run that load but I did experiment with it in my less experienced days. The point was that just because a round might make a mile doesn't mean its a good idea or anything close to accurate at that distance.

**Edited to add**

Now that I'm home I'll add to this a bit. My point when I made that comment was that just getting the round there doesn't mean much. In my newer days when I tried to come up with a round that would do it all I messed with heavy projectiles, long barrels, and hot rod powders. The 208 will get close to a mile supersonic, but that's irrelevant. There is a point of diminishing return where the cartridge is no longer viable against targets at that range. They had a practice target at 1250 or so at last years Cup, I hit it a half dozen times with as many misses with a 178gr projectile. I'd say that's within the scope of a 308's ability at altitude, though there are better calibers for the job. The year prior there was a target at 1450 or so and I had some ammo to burn so I tried to see if I could even tag it a single time. Never touched it.

That's my point. There comes a range where the cartridge is no longer effective. The flight time and the distance overpower the BC of the bullet and your odds of hitting a target drop off very steeply. I think that is also Frank's point about a 6.5 caliber to a mile. Just because it gets there doesn't matter if the slightest breeze dashes your hopes of hitting a target. There's a reason people shoot 338 and bigger to a mile. Bigger bullet, magnum velocity, high BC bullet. Even then you really have to be on your game at those distances.

I know the OP and he's asking a reasonable question. My answer is, I've not seen anyone advocating 45MOA mounts over 20MOA mounts, at least not for 6.5 calibers. Even if they did all that really does is maximize your scope travel. That caliber isn't suited to distances much past maybe 1100-1200yds though so its sort of a solution in search of a problem. If you put the same scope on a 338LM and you want to shoot to 2000 yards you will need all the travel you can get, but that's another story. The 20MOA mount is more than sufficient for what you will be doing, even when you venture past 1200.

 

[damoncali]

On a related note, the old thinking was that it was ideal to have the reticle centered in the scope at the range at which you are shooting because the optics ground in such a way that the aberrations are worse at the edges. Some bench rest shooters have been known to obsess over this in an effort to reduce group sizes by another 10 thous.

Now, I don't have a $3000 scope, but my 14 year old Nightforce looks pretty darn good from edge to edge, so my sense is that this advice has been rendered obsolete by modern optical engineering methods. Then again, I don't have one of those 50-80 power monsters, either. Is that the current thought? That centering the reticle is not something worth worrying about?

 

[Coloradocop]

I know the OP and he's asking a reasonable question. My answer is, I've not seen anyone advocating 45MOA mounts over 20MOA mounts, at least not for 6.5 calibers. Even if they did all that really does is maximize your scope travel. That caliber isn't suited to distances much past maybe 1100-1200yds though so its sort of a solution in search of a problem. If you put the same scope on a 338LM and you want to shoot to 2000 yards you will need all the travel you can get, but that's another story. The 20MOA mount is more than sufficient for what you will be doing, even when you venture past 1200.

That's sort of along the lines of what I was thinking, too. Thanks for the reply!

Now, I don't have a $3000 scope, but my 14 year old Nightforce looks pretty darn good from edge to edge, so my sense is that this advice has been rendered obsolete by modern optical engineering methods. Then again, I don't have one of those 50-80 power monsters, either. Is that the current thought? That centering the reticle is not something worth worrying about?

I don't know if there are some other issues with being at the "edge" of a scope (again, part of the reason for this thread), but I'd agree in saying that optical clarity doesn't appear to be one of them, at least with my scope. I'll pay closer attention to this when I'm at the range again (just to see if there's something I missed), but my memory seems to suggest that the scope appeared just as clear to me throughout the range of travel.

 

[6.5 GUY]

If you have 13 mrad of elevation, then you should have a total of 26 (13 up and 13 down) 13 Mrad rounded nicely is basically 45 MOA so you will most likely have 45 MOA up, and 45 MOA down. Since you do not want to be looking on the edge of the glass for a 100 yard zero, I would stay up at least 15 MOA so that leaves you with 30 MOA before you are at the center of the optic. I would get a 30 MOA rail and this will give you a total of 75 MOA of elevation, or in your case about 20 Mrad.

So to answer your question, a 30 MOA rail would be perfect for that scope on a 6.5 x 47 if you are planning to do 1000 yard work. If you do not plan to shoot much at 1000 then drop it down to a 20MOA base which would be ideal for the 500 to 700 yard range.

RHunter from what you are saying has me wondering if I am interpreting the actual specs. wrong or am I miss understanding the total elevation adjustment on Schmidt & Bender website for the 4-16x50 PMII/P? They say "0-13 Mrad of elevation" . I read that as a total of only 13? Not 13 up and down which would be 26 Mrad of adjustment? Or am I miss understanding that?

I wondered why this particular scope had so little of scope adjustment range, 0-13 Mrad, 0- 130 cm, or 0-56 moa. If I do the math for the Mrad version and the CM version they both have the same total amount of elevation adjustment in inches, 46.8", which they should since the tube erector's are the same except for the actual markings on the turrets, Mrad or cm. I was puzzled by the fact that the MOA version has 9.2" more elevation (0-56), but since cm and Mrad are both the same as far as dismal point, 1 cm = .36" and 1 Mrad = 3.6" the figures given on the S&B website must be correct. That being said I would have thought since AI used 28 or 29 MOA bases, that is half of the 56 MOA total elevation within the scope, and why they used that number?

But the cm and Mrad are different in that the total amount is only 46.8 MOA, which had me thinking the odd number of 23.4 MOA for slope, and why the difference in the two (MOA vs. Mrad and cm)? And would a 25 MOA base or a 20 MOA base be not be used?

I have a 1300+ yard range at home, but it is not my preferred distance to shot only because I like making first round hits and not "Oh so close" misses. At that distance I prefer to use something a tad bigger, either my 300 Jarrett or the TRG-42 338 LM. But most of my shooting is 100-600 with some out to 900 yards at home on 8" and 19" steel targets using lighter recoiling less expensive guns and ammo.

Thank you and Frank "Lowlight" for the help, I appreciate it very much.

 

[RHunter]

0-13 Mrad of elevation

Is exactly that, elevation. ZERO is generally half way between the total scale of elevation and slope or in simple terms, zero is parallel with the scope body and in the center of the scope body.

You have to have slope (depth) of range or you would never be able to zero at close range using a rail with any slope.

as dismal point, 1 cm = .36" and 1 Mrad = 3.6" the figures given on the S&B website must be correct.

As far as I am aware, 1 Mil is actually 3.438" unless they changed it so your numbers are slightly off... When I convert the two I use 3.5 MOA to one Mrad or mill and call it close enough for conversation sake.

Now, I don't have a $3000 scope, but my 14 year old Nightforce looks pretty darn good from edge to edge, so my sense is that this advice has been rendered obsolete by modern optical engineering methods. Then again, I don't have one of those 50-80 power monsters, either. Is that the current thought? That centering the reticle is not something worth worrying about?

Everyone has their opinion on this but I think S&B is a much better product for clarity at the end of the sight range than Nightforce because I have used them side by side, same day, same range and there is a difference. You do get what you pay for in a S&B, it is a much better product than a Nightforce.

But before you accuse me of being some S&B fanboy, I will say I do not own one, but I do own 3 Nightforce 8-32x56 NXS' because of price and because the quality is every bit as good when using the scope in the center 2/3rds of its adjustment range.

Ultimately you guys can use whatever the fuck you want and believe whatever the fuck you want. I am not shooting any of your guns and I ultimately could care less what your experience is when shooting. I offered advice on picking a rail and explained how I come up with the slope recommendation in simple terms so any future reader could understand it. It is best practices advice regardless of the equipment you use.

If you want to get a rail that places you at the bottom of the adjustment range so you have a full 90+ MOA of elevation, go right ahead. You most likely will never dope that scope past the center line the entire time you own it... but then again, if it makes you feel all warm and fuzzy knowing you have enough elevation adjustment to shoot something in the next county, be my guest.

Okay, run your ballistics calculator for a 208 amax doing 2550

Oh, OK you are one of those 65,000 PSI guys... My Bad.

 

[emdeucee]

20 MOA should suffice, however I'm ordering a Ken Farrell 30MOA steel base because (1) I'm little over half way through my elevation adjustments zeroed at 100 yards with 20MOA,(2) I running steel rings and have an aluminum base so would like to upgrade to match, and (3) just because.

Bases are relatively inexpensive. The limiting factor to the amount of angle would be the range of adjustability of your elevation.

 

[RHunter]

The limiting factor to the amount of angle would be the range of adjustability of your elevation.

Should read: total range of adjustment since elevation is the adjustment range considered to be above the center line.

 

[6.5 GUY]

Wow, what is up with droping the "F Bombs"? But for the record Rhunter 1 Mrad is 3.6" @ 100 yards ...... the number below is what you thought was the answer?

I'll post this directly from what was taken from Mil-dot.com for anyone else you'd like to read it:

Note: Do not confuse the angular mil with the minute of arc (MOA).
1 trigonometric milliradian (mrad) ≈ 3.43774677078493 MOA. 1 NATO mil = 3.375 MOA (exactly).

Radians:

What is a radian? (Warning: you might have to read this paragraph a few times). A radian
is a unit of angular measurement. Officially, one radian subtends an arc equal in length to
the radius of the circle, “r”. (Yeah that helps). How about this. What a radian is it
associates an arc length, called a radian arc, which is equal in length to the radius of the
circle, with an angle at the center of the circle. The angle the arc created is called a
radian. Or, another way, it’s the angle created at the center of a circle by an arc on the
circumference of the circle, and that arc length is equal in length to the radius of the
circle. Think of it as a piece of apple pie, where the two sides of the pie (the radii) are
each equal in length to the curvature part of the pie (the arc). The angle created by the
three sides at the center of the circle equals 1 radian (Fig.1).



To find out how many “radians” (and /or radian arc’s) are in a circle, we use the
circumference formula of a circle, which is C = 2 r, where “r” is the radius. Take 2 r
and divide by r. (Note: = 3.14159)

2 r = 2 r = 2 = 2 x 3.14159 = 6.2832.
r r
Therefore, there are 6.2832 radians in a circle (or, 6.2832 radian arc’s that go
around the circumference of a circle).

No matter how long the radius “r” is, there will always be 6.2832 radians in a circle
(because the “r” ’s always get cancelled out in the arithmetic and all you’re left with is
2 ).

How many degrees are in a radian (or how big is the angle created by the radian arc)?
Since there are 360 degrees in a circle and there are 6.2832 radians in a circle, then there
are: 360/6.2832= 57.3 degrees per radian in all circles no matter how long “r”is. (Fig. 2
below). Since there are 57.3°in each radian, and there are 6.2832 radians in a circle, then
6.2832 x 57.3° = 360° in a circle. Make sense?
4
Fig. 2


(A) Minutes in a Circle

There are 360 degrees in a circle, and each degree is composed of 60 minutes (60’).
Therefore, there are 360 (degrees) x 60 (minutes) = 21,600 minutes in a circle (21,600’).

(B) Milliradians (mils)

What is a milliradian? A “mil” is defined as “one thousandth”, or 1/1000. Therefore, a
millradian is 1/1000 of a radian. Take each of the radians that go around a circle and
chop it up into a thousand pieces. Since there are 6.2832 radians in a circle, and each
radian is chopped up into a thousand pieces, then there are 6.2832 x 1000 = 6,283.2
milliradians in a circle. (Milliradians is usually just shortened to “mils”)

(C) Degrees in a Milliradian (or degrees per mil)

I need to find out how many degrees are in each milliradian. A circle has 360 degrees,
and/or 6,283.2 milliradians that go around it (B above). Therefore:



There are .0573 degrees per mil (degrees/mil)

(D) Minutes in a Milliradian (or minutes per mil)
I also need to find out how many minutes (referred to as minutes of angle, or moa) there
are in each mil. Let’s review. We have 21,600 minutes in a circle (A above). And we
have 6,283.2 mils in a circle (B above). Take 21,600 minutes and divide that by 6,283.2
mils and you will get 3.4377 minutes/mil. Let’s shorten that to just 3.438 minutes/mil.


Hang in there with me, just a few more things to figure out.




5
(E) Inches per Mil at 100 yards.

Look at the circle in Fig. 3 below. Make the radius 100 yards, or 3,600 inches long.
(1 yard = 36 inches. 100 yards x 36 inches = 3,600 inches in 100 yards).

Fig. 3


Remember earlier from Fig.1 (page 3) that all the sides of the piece of pie are equal.
Therefore, if one side is 3,600 inches, then all sides of the pie are also 3,600 inches (see
Fig. 4 below). So what is 1/1000 of any of those sides, which would also be 1/1000 of the
radian arc? Essentially, what is 1 mil equal to (remember, 1 mil is defined as 1/1000 of a
radian)? 3,600 inches/1000 = 3.6 inches. (The drawing is not to scale, but you get the
hint). Therefore, at 100 yards, 1 mil = 3.6 inches.

Fig. 4




For you math majors out there, another way to find the answer is to look at the bottom of
Fig. 4 as a triangle (enlarged in Fig. 5 below). We want to find the value of “x” in Fig. 5.
The way to do this is to use the tangent function of trigonometry.


We know the length of one side of the triangle, and the angle. But to use the tangent
function, we need to convert the angle that is expressed in “mils” into an angle that is
expressed in “degrees”. Remember from (C) on page 4, 1 mil = .0573 degrees. Now we
can solve for “x”.

Fig. 5


1) Tan θ = opposite 2) Tan .0573° = x 3) 3,600 (Tan .0573) = x
adjacent 3,600 in.

(NOTE: using your calculator, the tangent of .0573 is .001)

4) 3,600 (.001) = x 5) x = 3.6 inches

So 1 mil at 100 yards equals 3.6 inches.

Note: Even though the opposite side of the triangle “x” in Fig. 5 above is really not a straight line but a
curve because it is actually a part of a circle, it is a very small curve. At this distance and at this small of an
angle, for all practicable purposes we can consider it a straight line and its effects on the math are
negligible.

(F) Inches per moa

This next part could be confusing, so follow the units here. Remember from (D) on page
4, there are 3.438 minutes per mil at 100 yards. Also, from (E) on page 5, there are 3.6
inches per mil at 100 yards. The question here is how many “inches per minute” are there
at 100 yards? (Remember that ‘minute’ is an angular measurement like mils).

1) 3.6 inches per mil. 2) 3.6 inches per mil.
3.438 minutes per mil. 3.438 minutes per mil.

3) 3.6 inches = 1.047 inches/minute
3.438 minutes

There are 1.047 inches per minute of angle at 100 yards (1.047 inches/minute).

Honestly though I was asking a question for advise, and not turn it into a DOG FIGHT!

 

[LawnMM]

Oh, OK you are one of those 65,000 PSI guys... My Bad.

You are a little dense, aren't you? I'll try crayons. You said it's not possible to get a 308 close to a mile, I gave an example of how it's possible. I further explained how the entire point of the example is illustrating the futility of trying to push a cartridge past its effective range of a cartridge. I also said its not something I do currently, nor do I recommend trying it. Quite the opposite, it was more of a 'been there, tried that, its not worth it,' statement with respect to using cartridges outside their envelope.

Then I suppose this illustrates the differences between some people on the board. Some claim to know what's what from behind a keyboard and some go out and try it to see what's possible and what lessons are to be learned in the process.

Instead of trying to paint me as a reckless fool try reading what I said and you might just see I'm agreeing with some of what you are saying.

 

[RHunter]

1 Mrad is 3.6" @ 100 yards

You are correct, I fubard that once I re-read it, should have been Mrad not mil. Don't you think your statement in that post was not very clear because you did not mention you were calculating it for 100 yards?

But my statement is the same, when I convert the two to MOA (Mrad and Mil) I use 3.5 as the multiplier because it is close enough for conversation sake. Remember, we are trying to get a rough idea what the best slope for a scope would be. Doing all the math to the enth degree as explained above is rather pointless when there is such a large margin to work with.

This is what I should have said:

As far as I am aware, 1 MRAD is actually 3.438" unless they changed it so your numbers are slightly off...

And this part is exactly on point:

When I convert the two I use 3.5 MOA to one Mrad or mill and call it close enough for conversation sake.
[MENTION=27126]LawnMM[/MENTION]

Sorry, I apologize, but when I read stuff like this

My 308 is supersonic to close to a mile in Colorado but it's not a mile gun.

I think of all these guys that tell all these stories on how they shoot their 308's all day long at distances over 1500 yards, and hold x MOA.. you see crap like that and see what you said and there ya go, first thing you think is yet another keyboard commando.

The problem with making statements like you made is you get some young kid that thinks "well if this guy did it, then I am going to try it" because all these new know-it-alls think they can do something better than the last guy. It gives them a false impression of what is realistic.

You have to admit, pushing a 208 Amax out of a 308 supersonic to a mile is not a real bright thing to do safety wise and really not something we should bring up for the sake of the idiots that think they can do it better than you. Like you, I have done some wild stuff with some cartridges and pushed bullets faster than I should have but for safety sake, I never bring that stuff up so some dumbass decides to try it that same way this dumbass did.

What pisses me off and motivates me to use the F bombs is we take a discussion that is so basic and argue about every single statement... well my 14 year old glass is clear at the edge and maybe that is some benchrest shooters obsession...

Really? The advice that was given was sound. Just leave it at that, but no...

So here you go...

In optics, chromatic aberration (CA, also called achromatism or chromatic distortion) is a type of distortion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have a different refractive index for different wavelengths of light (the dispersion of the lens). The refractive index decreases with increasing wavelength.

Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point. Since the focal length of a lens is dependent on the refractive index, different wavelengths of light will be focused on different positions.

There are two types of chromatic aberration: axial (longitudinal), and transverse (lateral). Axial aberration occurs when different wavelengths of light are focused at different distances from the lens, i.e., different points on the optical axis (focus shift). Transverse aberration occurs when different wavelengths are focused at different positions in the focal plane (because the magnification and/or distortion of the lens also varies with wavelength).

These two types have different characteristics, and may occur together. Axial CA occurs throughout the image and is specified as diopters and is reduced by stopping down. (This increases depth of field, so though the different wavelengths focus at different distances, they are still in acceptable focus.) Transverse CA does not occur in the center, and increases towards the edge, but is not affected by stopping down.

 

[6.5 GUY]

You honestly did not understand what I was asking, and it had nothing to do with CA. But you feel the need to spew words across a page like diarrhea, and now you go off about CA? Since you don't own a 4-16 x50 S&B PMII or nor do you know for a fact that 0-13 Mrad is not the total amount of adjustment range? Why would I just "trust what you say? You still don't believe in using an actual true number..... a Mrad is really 3.6" at 100 yards but 3.5" is close enough?

There is a hugh difference (double) if a scope has a total adjustment range of 26 Mrad and 13 Mrad. I'll use your statement: "It is critical you know what the adjustment range of the scope is that you want to use and you can not use a rail with a cant that is greater than 1/2 of the adjustment range of the optic or you will NEVER have a 100 yard zero."

Using that standard rule of taking half of the elevation in MOA and use that for base slope would make a scope with over 90 MOA OK to use a 45 MOA base and the other (13 Mrad scope) need something half as much.

I personally have never heard a scope Company give that number when the scope is optically centered. And Ya I've owned a few scopes in my life, most Companies like to talk up about how much elevation their scopes have in them available! It seem correct to me that when AI and S&B were using the 4-16x50 scope, AI would but a 28 MOA base since S&B states the 1/4 MOA version scope has 56 MOA of elevation. But you seem to think that same scope with a different turret adjustment value would have almost twice as much range (26 Mrad x 3.6" = 93.6" @ 100 yards, when all three are the exactly the same inside. (1/4" MOA, .01 cm, 1/10 Mrad). Sorry, but my instinct tells me you're wrong, so I'll ask someone whom actually has/or does own one what is the total elevation within the scope truly is.

I at least I got a straight forward answer from Frank without all the fuss about correcting me when you aren't actually sure of the correct total elevation?

BTW, your comment about wasting money on a titanium base is with out merit. If I can shed some weight at all on something and make it better, money well spent in my book. Besides, I don't have "friends to impress", nor would I care too if I did! My whole life has been only impress myself, help others and do good in the eyes of God. But the physical properties of titanium has a number of benefits other then just weight savings:

Approximately three times stronger than 6061 Aircraft aluminum.
45% lighter than carbon steel, while being just as strong.
Incredibly corrosion resistant. Titanium is routinely used for seawater applications where stainless steels have failed.
Titanium has a very low coefficient of thermal expansion, so point of impact shifts will not occur due to scope base growth under varying temperature conditions. (Severe problem with aluminum bases).

I don't care to rehash this over and over again with you. I said thanks and for that you wanted to point out I was wrong when in fact I was correct. Leave it be and move on with something else. Best of luck and take a break from the verbal slamming on everyone here. It doesn't help the cause.

 

[Big_Rig_416]

everyone's an expert.

 

[6.5 GUY]

BTW, my first thought was to make the base 25 MOA or 20 MOA.

 

[ZombieMonkey]

everyone's an expert.

I stayed at a Holiday Inn Express last night!

 

[Big_Rig_416]

I stayed at a Holiday Inn Express last night!

I did too! Did your bed have too much MOA of slope also?

 

[ZombieMonkey]

I did too! Did your bed have too much MOA of slope also?

I didn't take much time to stop and really notice... it seemed to change often.

 

[Big_Rig_416]

I didn't take much time to stop and really notice... it seemed to change often.

Bummer. The movement must have been due to the changes in the base by thermal fluctuations of the crappy HVAC in your room. Holiday inn's are notorious for that ya know. Its those damn aluminum bedframes.

 

[RHunter]

You honestly did not understand what I was asking, and it had nothing to do with CA. But you feel the need to spew words across a page like diarrhea, and now you go off about CA? Since you don't own a 4-16 x50 S&B PMII or nor do you know for a fact that 0-13 Mrad is not the total amount of adjustment range? Why would I just "trust what you say? You still don't believe in using an actual true number..... a Mrad is really 3.6" at 100 yards but 3.5" is close enough?

Get over it, its just a fucking sloped rail we are talking about! The comment about CA was not directed at you. you act as if 1/10th of an inch is going to make a big deal over what rail to use.. 3.5"or 3.5 MOA who fucking cares, it is close enough to do a quick calculation on what rail should be used for what optic.

CA is the reason to stay off the edges of an optic because some of it can not be corrected easily in a lower priced scope, so if you have enough range, stay in the center of that range.

BTW, your comment about wasting money on a titanium base is with out merit. If I can shed some weight at all on something and make it better, money well spent in my book. Besides, I don't have "friends to impress", nor would I care too if I did! My whole life has been only impress myself, help others and do good in the eyes of God. But the physical properties of titanium has a number of benefits other then just weight savings:

Approximately three times stronger than 6061 Aircraft aluminum.
45% lighter than carbon steel, while being just as strong.
Incredibly corrosion resistant. Titanium is routinely used for seawater applications where stainless steels have failed.
Titanium has a very low coefficient of thermal expansion, so point of impact shifts will not occur due to scope base growth under varying temperature conditions. (Severe problem with aluminum bases).

Give me a fucking break...

 

[base]

20 moa here

 

[tackleberry2000]

Im using a 20 moa base. Kinda dont need it with the Horus retical since it uses 2/3 of the scope plus i can also dial in the dope. Had it when i was using a MK4 second focal plane scope and though i might have need for it. Dont think it will be necessary unless im at 1500 yards.

 

[nuclear_shooter]

BTW, your comment about wasting money on a titanium base is with out merit. If I can shed some weight at all on something and make it better, money well spent in my book. Besides, I don't have "friends to impress", nor would I care too if I did! My whole life has been only impress myself, help others and do good in the eyes of God. But the physical properties of titanium has a number of benefits other then just weight savings:

Approximately three times stronger than 6061 Aircraft aluminum.
45% lighter than carbon steel, while being just as strong.
Incredibly corrosion resistant. Titanium is routinely used for seawater applications where stainless steels have failed.
Titanium has a very low coefficient of thermal expansion, so point of impact shifts will not occur due to scope base growth under varying temperature conditions. (Severe problem with aluminum bases).

I don't care to rehash this over and over again with you. I said thanks and for that you wanted to point out I was wrong when in fact I was correct. Leave it be and move on with something else. Best of luck and take a break from the verbal slamming on everyone here. It doesn't help the cause.

Do you really think you'll feel the difference in weight on a heavy tactical rifle anyway? Added with the fact that nobody is complaining about broken scope bases (Aluminum, steel or otherwise), I wouldn't pay any more for Ti.

 

[6.5 GUY]

Do you really think you'll feel the difference in weight on a heavy tactical rifle anyway? Added with the fact that nobody is complaining about broken scope bases (Aluminum, steel or otherwise), I wouldn't pay any more for Ti.

Do you think you'd notice the weights savings Automobile Companies use when replaced with light weight components? Take for instance decreasing the weight mass in a valve train, and the pistons, the lighter they are the more efficient a motor becomes. You wouldn't notice that either but that doesn't mean it's not being done! Three decades ago there were very few all aluminum engine blocks and aluminum skins used in Automobiles, only air plains, race cars, and in Ferrari's. Now a days there are used all the time to increase performance and fuel efficiency.

Ounces become pounds, and it adds up with everything (what's in our pack, H20, etc. even boots) and not just to what we add to a firearm. So why stop there? If that was the case we'd still be using wood stocks!!! If you think more is better, lug the extra weight around. I'm sure a lot of men in the armed forces would love to reduce the total weight mass they hump around if they could? A lighter soldier is a better more efficient soldier, weight is just as much as their foe as is their enemy in most cases.

And no I didn't saying anything about broken scope bases..... for me its about speed, and less time waiting to recover from the effects of the total accumulated mass weight I'm packing around.

 

[damoncali]

Do you think you'd notice the weights savings Automobile Companies use when replaced with light weight components? Take for instance decreasing the weight mass in a valve train, and the pistons, the lighter they are the more efficient a motor becomes. You wouldn't notice that either but that doesn't mean it's not being done! Three decades ago there were very few all aluminum engine blocks and aluminum skins used in Automobiles, only air plains, race cars, and in Ferrari's. Now a days there are used all the time to increase performance and fuel efficiency.

Ounces become pounds, and it adds up with everything (what's in our pack, H20, etc. even boots) and not just to what we add to a firearm. So why stop there? If that was the case we'd still be using wood stocks!!! If you think more is better, lug the extra weight around. I'm sure a lot of men in the armed forces would love to reduce the total weight mass they hump around if they could? A lighter soldier is a better more efficient soldier, weight is just as much as their foe as is their enemy in most cases.

And no I didn't saying anything about broken scope bases..... for me its about speed, and less time waiting to recover from the effects of the total accumulated mass weight I'm packing around.

Aluminum is lighter than titanium. If that's your concern, aluminum is the way to go. There is a good reason so much space hardware is made out of the stuff.

 

[nuclear_shooter]

Do you think you'd notice the weights savings Automobile Companies use when replaced with light weight components? Take for instance decreasing the weight mass in a valve train, and the pistons, the lighter they are the more efficient a motor becomes. You wouldn't notice that either but that doesn't mean it's not being done! Three decades ago there were very few all aluminum engine blocks and aluminum skins used in Automobiles, only air plains, race cars, and in Ferrari's. Now a days there are used all the time to increase performance and fuel efficiency.

Ounces become pounds, and it adds up with everything (what's in our pack, H20, etc. even boots) and not just to what we add to a firearm. So why stop there? If that was the case we'd still be using wood stocks!!! If you think more is better, lug the extra weight around. I'm sure a lot of men in the armed forces would love to reduce the total weight mass they hump around if they could? A lighter soldier is a better more efficient soldier, weight is just as much as their foe as is their enemy in most cases.

And no I didn't saying anything about broken scope bases..... for me its about speed, and less time waiting to recover from the effects of the total accumulated mass weight I'm packing around.

This is obviously a false analogy. Cars have replaced one of the heaviest parts (engine) with aluminum alloys and parts of the body with plastics/composites. With guns, if you want to reduce weight, you generally do that in the barrel and stock. But I'm glad you can notice the fraction of a pound difference in your guns.

 

[6.5 GUY]

This is obviously a false analogy. Cars have replaced one of the heaviest parts (engine) with aluminum alloys and parts of the body with plastics/composites. With guns, if you want to reduce weight, you generally do that in the barrel and stock. But I'm glad you can notice the fraction of a pound difference in your guns.

Your comment was about weight savings. Which my reply was reducing the overall weight of an object, and each object being reduced by fractions of a pound will add up with each item added. Times that by everything you place on your body and combine that in very steep vertical country at high elevation and you'll be asking yourself what you do and don't need!

The barrel is last place I want to make a compromise in my opinion, that is unless your not concerned about accuracy as the barrel heats up. There are ways to stiffen a stock while reducing the overall weight which is better then taking it out of the barrel, and there is only so many parts to look to reduce the weight while still having durability and constancy.

I don't recall ever saying I could tell 3.2 oz. vs. 5 oz. added to a rifle's weight either, but I couldn't help but notice you don't mention where you live in your profile? Not a lot of flat ground around here, unless you're talking about the road surface.

 

[Dallas4rceMarine]

I can tell you that I'm able to dial 23.4 Mils up from my 100 yard zero as I'm currently setup.

I run 20 MOA bases on my rifles, most custom actions come with a 20 MOA base as well.

with my .260 23.4 mils will get me to 1,840 yards. That is past my supersonic range. not sure what rifle, bullet, barrel, muzzle velocity you have, but I think you have plenty there!