Need some advice!!

[scv_guy]

I'm building a nice target rifle to shoot 600-800 yards. Is a 20moa scope base needed and if so why?

[AreWeFree]

What cartridge are you using and how much adjustment does your scope have?

Depending on the equipment you're using, for 600 - 800 yards a 20moa base is most likely not needed.

Edit: I'm no expert but I read a lot during spare time. If your goal is 600 - 800 yards, then when you get to that goal you may want to try 800 - 1000 yards. At that point you may need the extra 20 moa adjustment, so having a 20moa base will not hurt you, but at under 800 with a 30mm scope tube and 90MOA total adjustment it isn't helping either.

90 MOA is 45 MOA in each direction, so adding a 20 MOA base will give you 65 MOA of adjustment for elevation.

[scv_guy]

Got it!!
The build is a Savage model 10 in .308 win

[AreWeFree]

Check the specifications on your scope to see the total elevation adjustment, then halve this number.

You can use a ballistic calculator and input your data to make a drop chart. From here you'll know how far you can shoot before running out of elevation on your scope.

Edit: There's many ballistic calcs out there, but here's a couple:

http://www.hornady.com/ballistics-resource/ballistics-calculator

http://bergerbullets.com/ballistics/

http://www.gseven.com/ballistic-program