40 moa base for .308, too much?

Haakman

Haakman

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Hi guys,

I have a ruger precision rifle (.308) on its way to me that has a 20moa (non removable i think) rail on it, and I plan to put my Vortex Razor HD gen 2 on it (3-18xffp ebr-2 moa model).

But that scope is mounted on a Spuhr ISMS 20moa mount. so when it goes on the rifle i'm going to have 40 moa just in the bases. In the past I had the scope on a lapua rifle with 30 moa in the bases and the scope zero'd at 100 Meters just fine, but the added 10 moa I'm not sure about.

What I'm wondering is, does anyone have an idea with a 40 moa base will I be able to zero it at 100 meters? the scope has 120moa in elevation so I think it might be able to go low enough but also is that good for the scope? like having the turrets dialed so far down are there any springs that i'm leaving compressed or anything like that?

This rifle is going to be my main rifle this year for long range gong shooting, varmint hunting and big game hunting so I plan to use it between 0-1200 yards. not sure on the specific load i'll use yet but I tend to shoot on the heavy side, atleast 178's.

I know I can flip the scope mount arounf and the two 20 moa cants will cancel each other out to make 0 moa, but my preference is to have atleast 20moa in the bases but I've never done 40.

Is that okay zeroing a scope way down at its bottom end like that? I know it will give me more use of the rest of the elevation in the scope my concern is, is that a normal thing people do or is that bad for some reason?


thanks for the assistance
 
If you can crank it down 10 moa more from your 100yd zero with the 30moa setup you'll be good to go. It should be fine running it like that. I know that some people will step up a scope like this so they have full elevation range. If you don't need 120moa to reach your max range then maybe you'd be better suited with a 0 moa base or get a good set of rings. Either way it will be your preference as a shooter.
 
I think you'll be fine, 120 is a lot to play with. I'd be more concerned with getting a 308 out far enough that you'd need that much elevation! :p
 
6MT said:
With that base, your zero should be @200.

And to hunt with that round out to 1200...? wtf?
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I never said I was hunting at 1200. if you read again you'll see that the rifle is being used for three things, one of them being long range gong shooting. I've never heard of a 200 meter zero, I usually always see 100 and 300, whats the theory behind zeroing at 200?


Alpheus said:
I think you'll be fine, 120 is a lot to play with. I'd be more concerned with getting a 308 out far enough that you'd need that much elevation! :p
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hey better to have it and not need it than need it and not have it haha! yeah 120 is a lot for a .308 but I figure with the bases having so much cant in them I'll end up somewhere close to 120 with a 100m zero, though I remember in the past shooting .308's Ive needed 86, can't remember the range though but I was chucking 208gr Amax's back then.

frank223 said:
If you can crank it down 10 moa more from your 100yd zero with the 30moa setup you'll be good to go. It should be fine running it like that. I know that some people will step up a scope like this so they have full elevation range. If you don't need 120moa to reach your max range then maybe you'd be better suited with a 0 moa base or get a good set of rings. Either way it will be your preference as a shooter.
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huh never thought about that thanks man I still have the zero stops in place on the scope from the 30moa setup I should disable them and see how much I have left over under that. we'll see how it zero's and how I like it, I'll probably never need 120moa of elevation with a .308 but flipping to two around to make 0 moa in the bases will potentially put a limit for the long range aspect, I'm just trying to see if I can pull off 40 moa without having to go buy new spuhr rings, I'd rather not spend $550+ for new rings just to take out 20moa.
 
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IMHO... You have plenty of play left in the elevation of your scope to make a 100 yd zero with a 40 moa cant. There is no mechanical reason inside a scope to counter having the erector spend the bulk of its life at 40 moa off its natural center. The only real difference in the angle of an erector within a scope is what portion of the lenses are being used. The center of any lens is always of the highest quality and most free of any distortion (more pronounced in cheap glass, but still present in the more expensive stuff). So, by using the upper portion of the objective lens for your close in shots where great glass isn't as vital, makes sense as well... and you will end up using a better and better portion of glass up to 40 moa drop.

In short, go for it.

Kosmic said:
lol! I got flamed a few months back asking the same question. :rolleyes: In my case it was a 20MOA rail + 20MOA Spuhr mount w/ a .308 rifle.

I decided to buy another rail (0MOA).....an option that you don't have.

http://www.canadiangunnutz.com/foru...eed-help-for-a-100yds-0-w-40-MOA-(rail-mount)

turning the unimount around would lose the bubble level?
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Yeah... by flamers with poor geometry ;)
 
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frank223 said:
Alberta Tactical Rifle Supply.... They have one of the best rings on the market. No cam lock, but rock solid rings and lot less then a Spuhr
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I've had atrs rings in the past, as well as nightforce and many other brands, nothing against them your correct in what you say but for me the spuhr rings have built in anti cant levels on them plus I already have angle cosign indicators mounted directly to the spuhr rings, If I went with traditional style rings like atrs brand I would have to get a new anti cant level and a new mount for an angle cosine indicator. I don't want to lose any of that indication and if I'm going to spend money I'll just bite it and get another set of spuhr rings as I already have four rifles setup with them and spare accessories, screws etc for them, they're very configurable that way I've even put on 45 degree offset burris fastfire on a semi auto with spuhr rings.

The idea or my original question is weather I can make what I have right now work. buying new equipment is not a problem for me, but the answer can't always just be "buy new stuff"
I get what your saying ya, I can buy nightforce rings, get the anti cant level ring with the cosine indicator mount for cheaper than spuhr, but I like the spuhr system I have setup across all my rifles and just wanted to see if it could work with the 20moa rings stacked on the 20moa base. know what i mean?


Kosmic said:
lol! I got flamed a few months back asking the same question. :rolleyes: In my case it was a 20MOA rail + 20MOA Spuhr mount w/ a .308 rifle.

I decided to buy another rail (0MOA).....an option that you don't have.

http://www.canadiangunnutz.com/foru...eed-help-for-a-100yds-0-w-40-MOA-(rail-mount)

turning the unimount around would lose the bubble level?
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ya thats exactly what my question is, 20moa rail/base + 20moa rings, heh, must be the weather or something.

yeah thanks man forgot about that flipping the rings would lose the level, 40moa or bust then i guess!
 
FF57 said:
IMHO... You have plenty of play left in the elevation of your scope to make a 100 yd zero with a 40 moa cant. There is no mechanical reason inside a scope to counter having the erector spend the bulk of its life at 40 moa off its natural center. The only real difference in the angle of an erector within a scope is what portion of the lenses are being used. The center of any lens is always of the highest quality and most free of any distortion (more pronounced in cheap glass, but still present in the more expensive stuff). So, by using the upper portion of the objective lens for your close in shots where great glass isn't as vital, makes sense as well... and you will end up using a better and better portion of glass up to 40 moa drop.

In short, go for it.
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Thanks much appreciated this is what I was looking to hear about, if there's no mechanical concern and I'm not using the highest quality portion of the lens at 100 that is not a big deal to me at all; and if it brings me to center lens at extended ranges where clarity more critical then ya I'll have to give it a try. will post an update on here once I find out. thanks again man!
 
You are fine at 40 MOA, and with the amount of travel on that scope you should be able to get away with 50 MOA..... 35.9 mil total elevation in that scope...devided by 2 is almost 18 mil....40 MOA is just shy of 12 mil add the two and you have 30 mil or 100.1 MOA total use out of that scope so if looking to use for all around longrange it's all good, And you will be just fine with that set up to reach out to a mile or so
 
You should be fine with that combo. If you are truly going to 1200 then the more the merrier. That is a long shot(not unachievable) but long with a .308. I hope you have great glass in your spotting scope and a partner that can keep up. Those will be far more important than the amount of MOA under your glass.
 
Longshot said:
You should be fine with that combo. If you are truly going to 1200 then the more the merrier. That is a long shot(not unachievable) but long with a .308. I hope you have great glass in your spotting scope and a partner that can keep up. Those will be far more important than the amount of MOA under your glass.
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Thanks but I'm not new to long range shooting, I shoot 1800M to 2000M with my lapua on gongs by myself regularly, mind you though a 300gr smk still absolutely rocks a gong at that distance so it's not hard to spot when you hit or see dirt fly where you miss, the last .308 I had it out to 1065M by myself. long flight times and good scope clarity I can usually see whats going on, if the projectile doesn't shake the gong you can usually see fragmentation on impact. I know I'm tacking another 200 on there but I think I can handle it as I'm accustomed to shooting much farther with the same powered optic.

I know how to shoot, I'm just not sure on the mechanics inside the scope in regards to being spun all the way down like that all the time, equate it to most people know how to drive very well, but aren't mechanics.
 
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