20 MOA base dilemma

Something is not adding up here. If you bottomed out with a 20moa base, then switching to a 15moa base should only yield 5moa or less of down travel left. Somehow you have an additional 12moa by only changing the can't of the base 5?
 
Regardless of the click value... The amount of actual mechanical travel does not change. I too am confused by the 12moa increase with a 5moa difference in the base
 
There's no mystery here. He was 1.5-2 MOA high on the old base, and now has 12 CLICKS (aka 3MOA) of down adjustment available. So changing the base a nominal 5 MOA gave him a measured result of 4.5-5 MOA of adjustment he didn't have before. I'd hate to see y'all try to zero a rifle :D
 
Well, I misread it too...
And now, it doesn't make sense, at ALL.

How can the OP have only 12 CLICKS of down adjustment left at 100 yards?? That's only 3 minutes...

That would be incorrect even with a zero m.o.a. base. Even more so with a 15 minute base.

I'm assuming he meant 12 minutes- which still isn't what it should be.

Roughly 20 minutes down available from the scope according to what has been posted, two inches of drop at 100 yards should leave 18 available after 100 yard zero. Add fifteen minutes down angle base, = 33 MINUTES available beyond zero,

Either the scope is defective, or something is REALLY screwed up with the receiver on the rifle being out of spec affecting the mount angle. My bet is that the scope is out of spec, since the odds of the receiver being CNC'd out of spec by that much are slim, and none...
 
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My first question is do you really need a 20 moa base ? You say your building a "long range" rifle , but what do you consider "long range" ? Long range starts at 800 yds. I shoot out to 600 yds on a weekly basis and most of your better quality target scopes have the ability to dope out to about 750 yds based upon your average 30 caliber pushing a bullet at about 2600 fps. On my R700 precision .300 win mag I'm using a Sightron SIII and reaching out to 800 yds with a standard 0 moa rail is NO problem. I can almost get to 1K but by the numbers I'm only left with about 2 moa of additional elevation after the dope so for getting to 1K yds I did buy a 15 moa rail.
 
Road_Clam - to try and answer your question. I consider "long range" anything over about 300 yards :)

This project is just something I am playing around with. I don't even have regular access to a range that has targets beyond 300 yards. Who knows when, or for that matter if I will ever shoot at the ranges this rifle is capable of, realistically 800-1,200 yards IMO.

What I wanted to build is a basic rifle that when or if opportunity presents itself to shoot out to 500-1,000 (+\-) yards I could. So while anything other than a regular scope base may be not needed for my purposes, I wanted to get a base capable of giving me the most elevation potential.

From everything I see the 15 MOA base was the way to go. And for those who may add up numbers and say something still does not seem correct, I can only say those were the results I got.

I am learning as I go along. Both about the build, and ballistics which will be running on a computer program, based off of my loads chronographed information.

If I am throwing anyone off with my verbiage I apologize.

FWIW - with the rifle sighted in "dead on" exactly at 100 yards, with Federal Gold Metal Match 168 grain ammo, my scope is exactly 29 "clicks" away from being bottomed out - or not being able to make any more downward adjustments. So where I wrote 12 clicks previously was wrong - At least now that I am using the 15 MOA base. With the 15 MOA base I have 29 clicks of downward adjustments left.

Again thanks for all the comments and input.

Rob
 
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Rob62 , I would suggest building your rifle based upon what you WILL be shooting as far as distances, not what you would "like" to "maybe" shoot. Your potentially adding a lot of close range zero problems when you are running a 20 moa base on a short range rifle. Me personally would just fit your rifle with a 0 moa rail, and then "if" the 1000 yd distance presents itself then I would just swap out to a 15 moa rail. (strictly just my opinion). I run MGW rails and they are a great rail for very reasonable money. At my gun club I need to be able to shoot anywhere from 100 yds out to 600 yds as the norm, but I also needed to get my 300 WM out to 1K when I took the Sig Sauer reach for a thousand instructional class. So at that point I swapped my 0 moa rail for a 15moa. Worked great I was still able to obtain a 100 yd zero , and also get out to 1K. I did not get a 20 moa rail as that would have put my 100 yd zero at risk of not having enough "bottom" elevation with my Sightron scope after testing my scope's adjustments. It all depends on where the factory set the 100 yd zero relative to the range of elevation adjustments on your scope.
 
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It all depends on where the factory set the 100 yd zero relative to the range of elevation adjustments on your scope.
Click to expand...

Not sure what you meant by this- but no manufacturer "sets a 100 yard zero" before the optic leaves the factory. No way this could be possible anyway, as every round has different drop even at 100 yards.

I'm not aware of any manufacturer whose optic (intentionally) leaves the factory with its windage and elevation set in any way other than centered in their range of adjustment.
 
tobnpr said:
Not sure what you meant by this- but no manufacturer "sets a 100 yard zero" before the optic leaves the factory. No way this could be possible anyway, as every round has different drop even at 100 yards.

I'm not aware of any manufacturer whose optic (intentionally) leaves the factory with its windage and elevation set in any way other than centered in their range of adjustment.
Click to expand...

Speaking strictly from experience with my target Sightron SIII 8-32x and my Sightron 36x the 100 yd zero was set not in the "middle" of the elevation but more in the "lower" range of adjustment. When I established a 100 zero I did a test of how much lower moa adjustment I had available , and by my numbers I only had about 5 MOA of additional drop. High power target scopes need to be able to have the elevation capabilities to dope out to 600+ yards. My lower power hunting scopes are a totally different animal, and with that application yes, the typical 100 yd zero is in the middle of the adjustment range. I was almost able to take my Sightron 8-32x out to 1000 yds without the need of a 20 moa scope base, but after testing my scopes' elevation adjustment capability I would have only had an additional 3 MOA of adjustment according to my ballistics app, so that was cutting it too close IMO so I ended up adding a 15 MOA scope base.
 
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