Scope to barrel alignment thoery...

Okay, I am real big on getting the gun and scope on bulls eye by moving the basses around and then using the Burris posi-align inserts and last using the turrets to get the reticle on POI. Thus keeping the scope as close as possible to it's optical center.
So my question is, lets say your rifle shot six inches to the right and all you did to correct was adjust your windage turret to put it on the bulls eye. Will the rifle/scope be on target windage wise at all distances like 200 and 300 yards or will the bullet be angling off to the right again.

Who knows?

Charlie

I'll give it a shot... there is only one reticle in the tube. So adjusting it with knobs until it is dead center over a perfectly aligned barrel/receiver should have it aligned at any distance. That's theory.

In reality I guess there are no perfectly aligned barrel/receivers. The slight misalignment causes a little/lot of left/right shot placement to the desired point of aim. So knob adjustments are going to correct that reticle somewhere off-center in the opposite direction of the mechanical misalignment to make the bullet hit where you aim.

So I think I am with you.... guns needing significant correction via windage knobs or adjustable bases or ring inserts can be corrected to a desired alignment of aim and bullet strike at a desired distance. But moving past that I would think the scope correction would continue to over correct. That is why I personally was worried about using my scope or inserts to correct for 25" of initial windage.

I am no expert however, I think that once you get the gun zeroed the windage will not change at a further distance. I say this because your barrel and scope are out of align by a given moa value (in the given example it was a little under 6 moa at 100 yards). This misalignment is linear. If you are off 6 moa at 100 you will be off 6 moa at 1000 and therefore if no other external forces are acting on the bullet once you correct for the alignment problem it will be corrected at all distances. Again I am no expert but I have seen this in my own shooting. I have a rifle that has 15 moa left windage at it 100 yard zero. when I shoot it at 200 yards using my 100 yard zero the groups move down the target by 1.5 moa but are still in line with my point of aim. To fully prove this I should shoot at longer distances however, the further out you go the probability of an external force (extra wind) acting on the bullet increases.

If the scope has any cant in its mounting that will throw it off a bit.
The natural rotational force of the bullet is said to effect such things.
From 100-300yds both these things are basically inconsequential.
Even on a "no wind" day the moving atmosphere will cause more clicks ;D

I'm just a short ranger myself. The long range guys would have more than theorys.

Quote:

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Originally Posted by chemist1

I am no expert however, I think that once you get the gun zeroed the windage will not change at a further distance. I say this because your barrel and scope are out of align by a given moa value (in the given example it was a little under 6 moa at 100 yards). This misalignment is linear. If you are off 6 moa at 100 you will be off 6 moa at 1000 and therefore if no other external forces are acting on the bullet once you correct for the alignment problem it will be corrected at all distances. Again I am no expert but I have seen this in my own shooting. I have a rifle that has 15 moa left windage at it 100 yard zero. when I shoot it at 200 yards using my 100 yard zero the groups move down the target by 1.5 moa but are still in line with my point of aim. To fully prove this I should shoot at longer distances however, the further out you go the probability of an external force (extra wind) acting on the bullet increases.

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Chemist1 is quite correct, and stated it rather well. I've highlighted the 'Buzz' sentence. The linear alighnment, once correct for by either turrets, inserts, bases etc, puts the the scope reticle in congruence with the bullet path.

Like Harriershot, I also use bases (Weaver) and Burris Signature Zee rings w/ inserts to do 99% of correction. I want the reticle as close to optical center as possible.

[img width=600 height=399]http://i137.photobucket.com/albums/q228/ultramag44/Savage%20Bench%2012/SavageWeaver2.jpg[/img]

On a Savage (or most any other rifle) the scope mount holes drilled in the receiver will not be perfectly aligned with the axis of the receiver. Also, the axis of the barrel and the axis of the receiver may not be perfectly aligned. This means that the line of sight (looking through the scope) and the axis of the receiver are probably not exactly parallel when looking down at the rifle. If we had a perfectly accurate rifle we could see that the bullet will actually cross from left to right (or right to left) as distance increases. The term for this is parallax. Sighting in a rifle at longer distances will minimize this error. However, in practical terms this is an extremely minor error that will not be a factor if you sight in at longer distances. If you tried to sight in at 25 yards only then the error could be large.

Keeping a scope near the optical center is beneficial for other reasons than the parallax issue discussed above. Scopes tend to track better near the optical center of the adjustments. That is why the offset rings or angled scope bases (example 20 MOA) scope bases are popular.

Happy shooting!

Keith

I like what chemist1 has to say. I think the proof is in the pudding. I have never target shot out past 100 yds. but someday I will get to test this myself. Chemist1, I hope one day you get to test it out even farther but it sounds like you have proven once you are on target, your on.

Charlie