Noobie just trying to learn


Active Member
Aug 20, 2012
Just got a new rifle that has a 20moa picatinny rail already installed. Does this mean that if I have a scope with a max elevation of 65moa I will actually get 85moa at the muzzle? If I have my rifle zero'ed at 100 yards, if I am aiming for a target that requires 20moa for my specific load is my scope then going to be at a zero adjustment point(like coming from the factory) then I have the actuall 65moa of elevation still left out of the scope. I am new to using moa's and have never used a base with a angle built it. If I am creating a DOPE card do I have to account for the rail? If so how does it work? If I am shooting at a target lets say 250 yards away and I have it dialed in with 2 and 1/4 moa's on my scope, does that mean my muzzle is actually at 22 1/4 Moa's? Either I am really just over thinking things or I am really confused. I am in the process of deciding a scope and my goal is to do really long range shooting 1500yrds+. I am looking into the Vortex Viper PST 6-24x50 which has 65 or 67(one of the two) moa's of max elevation adjustment, which will get me out to about 1600 give or take. Unless you factor in the 20moa rail which will actually give me 80+ moa's which will get me out to a mile+. Any advise/help would be great!!!
You are some what correct. The 20 moa base increases your scopes ability to increase your vertical adjustment. Basically a scope will have lets say 40 moa of vertical adjustment. 20 up and 20 down. The 20 moa base makes you lower you scope adjustment 20 moa to zero you rifle . Say you zero at 100 yards. You have basically taken all you down moa adjustment, which you would not use and turned it into verticle upwards moa thus making your scopes ability 20 moa more than its stock configuration. Hope this helps you, steve
If your scope has a total elevation adjustment of 65 MOA (like a Viper PST 6-24X50), it has +32.5 and -32.5 MOA adjustment for the mechanical center. Your 20 MOA rail give you an additional 20 MOA adjustment up, relative to a standard base.

However, unless you have a custom rifle with a trued action and a very straight barrel, your factory rifle could have up to 20 MOA of error in any direction between the scope base and rifle bore at the muzzle. That error will add or subtract to the 32.5 + 20 MOA that you think you have. You won't know how much up adjustment you really have until you mount a scope and boresight it to the rifle.
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