20 vs. 40 MOA Scope Base

That scope will give you 90 min of elevation, generally if you zero at 100 yards you can assume you will have at least 45 min left, depending on the height of your rings.

With a 20 min base this gives you 65 min of elevation, from a 100 yard zero. With a 175gn bullet at 2600 fps I need ~ 40 elevation to reach 1000 yards, With the 65 minutes of elevation you could reach 1300 yards, and if you add a 40 min base you are out to 1500 yards, I am sure you are not looking to shoot that far with a .308, I would stay with the 20 min base that way you can get a 100 yard zero and reach all the way to the useful extreme of your rifle
 
in this case i think that the 308 is the limiting factor, i would recomend the 40 base if you have no intention shooting close. i have a 20 base and can 0 at 100 yards but never shoot my rifle there so that is useless to me, and just means more turning to get out to the useful range. a friend has a 40 base and cannot 0 closer than 400 yards, but who cares. the gun is meant to shoot long and the 40 base allows more useful vertical adjustment. the cost is the same, so if shooting close is a non issue go for the 40 base.
 
I know a couple of people who use a 20min rail and the closest they can zero is 300m which is about 4 mins from bottoming out the scope.

Mine zeros at 100 no problem and we are all using the same scope. 3 different actions.

1 of the rails that can't zero lower is Ian Robertsons rail on a Barnard, the other rail that can't zero under 300 is a Farrel base on a Nesika action and mine, that can zero lower, is a Farrel base on a Rem XR action.
 
armorman said:
Most of the posts I read about bases center on the 20 moa bases. Just wondering why most of you prefer the 20 moa bases rather than others that offer more slope? Is it because a larger slope such as a 40 moa base limits you from making proper elevation adjustment if you want a zero at 100 or 200 yards? I'm thinking of possibly upgrading my scope and for sure my base and rings. I hardly ever shoot at less than 300 or 400 yards so I'm not overly concerned about adjustments at close range or even a 200 yard zero. Right now I'm using standard Leupold rings and bases and I'm running out of elevation adjustment at close to 900 yards. Calibre is 308 and the scope is a vx111 6.5-20x50 lrt. Would a 40 moa base work for me since i'm not worried about anything less than 300 yards?
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Your scope has 90 moa of total elevation. Your base is flat so you should be at about 45 moa from the bottom of elevation adjustment, to zero at 100 yards, if you need 45 moa to get to 1000 yards there is something really wrong with your loads or your rifle.
308s shooting 175 gr SMKs normally only require about 35 moa or less to get to 1000 yards.
To go plus 20 on a decent rail and set of rings using your present scope should easily get you beyond 1400 yards and still be able to zero at 100 yards.
A plus 40 with your scope may allow you to still zero at 100 but I doubt you will ever have enough range to use the extra moa the rail offers.
 
While on this subject, how about a NF 12X42 NXS series scope?
Mounted on a bolt action .308 also, does one need 20 MOA bases for use out to 1000 yards, with either 155 to 170 grain bullets?
No hijack intended armourman!

Cheers..................
 
I have a Badger 20 minute base on my .308, and the ring system on my S&B gives me an additional 20 minutes. In order to have a 100 yard zero I had to move the rings two notches ahead on the Badger base which drops the scope closer to the bore of the rifle.

With my old scope the 20 minute base was zero at 100 yards at the scope's lowest adjustment and I doubt that you need more.
 
No, low rings not the problem. A 20 min base would give you lots of long range. At least 1200 yards.

Have you tried one of the 155 gr bullets, like a Sierra or Lapua? I use about 30 min to get them to 1000 yards. 2950 fps from a 30" barrel.

The 175 Sierra is a good bullet, as is their 190. Just avoid the 168. It is more wind sensitive and not good for long range.
 
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