Home Forums Hunting & Shooting Long Range Hunting 20 MOA Scope Base

At what point does a 20 MOA base become necessary?

That depends on the adjustment range of the scope, the trajectory you're working with, and the distance to the intended target.

When you run out of adjustment in your scope for shooting at longer distance. A scope with a lot of adjustment range (like a 30mm tube for example) is less likely to need a 20 moa base than say a 1" tube with less adjustment range.

Any way to determine this before you build?

a lot of 30mm tube scope have less adjustment than 1" tubes do. most will out of adjustment between 600-700yds

Know the trajectory of the round you'll be shooting.

Know the distance you want to shoot.

Know the adjustment range of the scope you will use.

Take into account you may use up some of the available adjustment sighting in at your zero distance.

Reading and Research.....helps a lot!!

Beat me to it. What he said...

As an example - say your scope has 15 mils total vertical adjustment. If we assume for sake of discussion that your zero is in the middle of travel, that leaves about 7.5 mils you can dial up for distance shooting. A quick look at a ballistic chart for your 308 shows you can expect to run out of adjustment somewhere around 800-850 yards. If you want to dial for longer distance with that scope, you'll need more elevation built into the scope mount, via a 20 moa (or more) base.

On the other hand, if you're using a larger tubed scope with say 36 mils of adjustment, you'd be able to dial to 1100-1200 yards with a flat base.

If in doubt, there's not much downside to a 20 moa base.

Appreciate the input. I plan to limit my shooting to no more than 600 yards with my 280, 7 Wby, 308 or 300 WSM.

Everything below zero on the erector,is 100% fhuqking USELESS. Hint.

20MOA inclination,is a joke,at best.

Hint.................

With a 22LR You'll need one sooner than later.

For longer range 22LR, I started with a 30MOA, and probably should have gone with more. Oh well.

you can always addburris xtr sigs with inserts to get more slope

I shoot alotta 75 MOA 1913 extended rails for Anschutz 54 Rimfire Fun. KILLER setup. With all the inclination in the rail,one can use a lower ring height. Hint.




6BR assembled on Saturday,coughed up 39.6 Mils remaining on it's erector,after a 20yd 105 Hornie BTHP zero. Burris steel 25MOA 1913 rail base inclination and 'Horn's wearing all 40MOA,to secure the 6x MQ.




No zero-stop requisite,as less than a full revolution remains on the erector.

Hint..................

We don't need no 20MOA base!!

Dimick Caplock Rifle by .com/photos/61286670N08/]Sharps Man, on [bleep]

At 1,000 yard many stock rifles run into the end of thier adjustments, which is never good for a scope (you want it to be more to the center).

Typically it starts at 800 yds so my rule of thumb - if it’s a 800 yard + rifle ... get 20 MOA rail, if it’s over 1,000.. think / research 30/40.. or more.
With 600 yards, and a 30mm tube you are typically OK... I’m sure there are exceptions.

I would focus on your typically target range, vs. the furthers range you’d shoot..

Meaning Easter woods hunting 600 yards is an exception (0 MOA is reasonable), Midwest / Western plains like West KS, anything under 300 is really rare - it’s more like 500yds is a common shot. (I’d think 20 MOA)

Built off Stith components? I like that rig, very cool.

If your shooting 1000y you need it. Remember if a scope has 60-70 total MOA, you divide by half and sometimes more just by the mounting system. This is just my 2 cent worth. The smaller the tube diameter the less travel you have as another poster mentioned. Large tube diameter usually give you more MOA adjustments at long distance, but not always.

Don't forget about vignetting. The outer 2-3 MOA are obscure on most scopes depending on quality.

Stick, do you keep the erector at the center and make elevation potential from the rail and ring insert combinations and hash marks? Does keeping the erector somewhat centered improve optical quality and maintain mechanical quality of the erector? I ask because of your statement of being below zero is a waste.
Thanks