20 moa Base question
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Broz
Well-Known Member
Its kinda like this in a nut shell. A scope mounted perfectly flat or on the same plane as the barrel, will zero with the scope elevation adjustment being close to the middle of adjustment. Using a "canted" or "tilted" base points the scope downward allowing you to be closer to the bottom of the adjustment when zeroed. Which in turn allows more adjustment on top that is used to dial up for longer shots.
Hope this makes sense.
Jeff
el matador
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- Jul 30, 2008
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At 100 yards you need about 3.5 moa to get zeroed (1.75" scope height, 1.95" bullet drop with 0.1 second t.o.f.). At 200 it's actually about 5 moa now that I look at the calculations. I'm not trying to argue, just stating accurate information. Most people would assume they're going to get a full 20 moa plus 1/2 the scope travel after they're sighted in but that's usually not the case
Broz
Well-Known Member
At 100 yards you need about 3.5 moa to get zeroed (1.75" scope height, 1.95" bullet drop with 0.1 second t.o.f.). At 200 it's actually about 5 moa now that I look at the calculations. I'm not trying to argue, just stating accurate information. Most people would assume they're going to get a full 20 moa plus 1/2 the scope travel after they're sighted in but that's usually not the case
Yes, I agree with what you are saying. But please read what you quoted from my post again. What I said was again
"With 100 yard zero..... the Line of sight Difference is more like 1.5 moa" You say 1.75" . That is line of sight above barrel bore. Right? I didn't mention drop or bullet path.
My math, 1 moa at 100 yards is 1.047" x my 1.5 moa that equals 1.57" so dependent on our scope height your examples are .180" of an inch above mine. less than one click.
I agree with your calcs for dial up after. But have mounted a bunch of Nightforce NXS's in .885" rings over a NF 20 moa rail and got the full 70 moa. of elevation from the 100 moa scope. Or within a click or two. However I realize it could go the other way too. Thus the reason I stated more than once "In a perfect world" which we all know is not the case. You well know that those 3.5 moa you are talking about could very easily be added to the dial up too if the rear of the receiver is a little high or the rings a few thousands off or what ever of the many errors that come into play. No, its not a perfect world, but the error could just as easily go towards 3.5 more dial up as less.
Jeff
Broz I value your knowledge and help here on the forum. I shoot several rifles 280ai and 6.5 saum and use 0 moa bases and both rifles have NF 5.5x22 nxs. Max that I shoot is @ 1000yds, is there any negative when your dialing close to the upper range of the scopes moa range. Like in the 35 to 40moa range. Thanks
Broz
Well-Known Member
Never had it be an issue with a NF. However I never max them out to the last click. You should be well under that with your advertised 100 moa of total elevation. Some people do like to work closer to the center of available elevation. But as I said it has never been an issue for me.
Jeff
bstomper
Well-Known Member
Just picked up on this conversation and learned alot. I always wondered what the 20 MOA rails meant. Now I know. I Think. So now with the scope canted downward when my balistics calc asks for the scope height, at what point of the scope/rifle do I measure that at. If i had to take a guess I would say directly above the chamber area. Correct.
