Physics of shooting a rifle

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Ahha. That's it. 1.5" above bore on rem 700, 2.5" on AR. 1" at 5yd adds 20moa. The method needs modification.

I will sharpie a dot above the screw head by the amount (sight height - 0.5"). Bore on the screw head. Sight on the dot. It will be on paper. Guaranteed.

Very good. Let's go down into bore sighting rabbit hole a bit more. I never use any those laser gadgets. How about them guns that don't allow me to see through the bore. I have my method. What is yours?

-TL



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tangolima: grab a pair of sizors and open them slightly not the distance apart of the cutting ends and the handle ends, then open them further and look. that's the difference in scope hight above the bore. as scope hight increses poi -vs- los increases. at a given range, the liength of the sizors
 
The cheapy lpvo with 30mm tube on the AR had no problem doing it. 2.5" at 5yd is 50 moa, which is quite a bit indeed.

For the rem 700, 1.5" at 5yd is 30moa. The scope was an old redfield with 1" tube. No problem either.

No canted rail in either case. Probably the scopes were about to max out.

-TL

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In order to bore sight a rifle that doesn't allow looking through the bore, mini 14 for instance, I have struggled with different methods; mirror, reflector etc.

Then it hits me. Why am I doing this? To get on paper, is it not? I just pull in the 24"x24" target really close, say 10yd. Fire one shot with sight right on the middle of the target. I will have to really screw up not to be on paper. Adjust turrets to put poi under poa by amount equal to sight height. Fire another shot to confirm. Push the target back to 100yd and fire again. It will be on paper.

That's how I bore sight without sighting through the bore. It always work. Why don't I do it for all guns? I could. But it involves calling the range cold to move the target. I only do that when I have to.

-TL

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Let's try another light one in optics, shall we? It is actually based a discussion on other forum. There they were discussing shift in poi caused by phoria. The op had such medical condition that his eye ball shift slightly when the other eye was covered. He noticed significant poi shift when shooting with both eyes open or one eye closed.

Members were perplexed. Everyone scrambled to do his own test. I believe it is parallax. What think you?

Say it is a FFP scope with 100yd fixed parallax. The reticle in the tube is located 8" in front of the shooter's eye. The target is at 50yd, so there is parallaxing going on. If the shooter's eye shifts 0.01" to the left, which direction will the reticle appear to shift in his field of view? If he adjusts his aim to realign the reticle and target, the poi will shift. By how much?

-TL


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both my ar's 10 and 15 are zeroed at 100yds and both will hit low at any shorter range (ANY SHORTER RANGE) so the 100yard mark is the first crossing of the trajectory and line of sight, that's from imperical testing not just calculations.

now it should be noted that the sights are 2.5 and 2.75 inchs above bore respectively. and the speed of projectile matters too.
 
georgehwbush said:
both my ar's 10 and 15 are zeroed at 100yds and both will hit low at any shorter range (ANY SHORTER RANGE) so the 100yard mark is the first crossing of the trajectory and line of sight, that's from imperical testing not just calculations.



now it should be noted that the sights are 2.5 and 2.75 inchs above bore respectively. and the speed of projectile matters too.
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100yd is indeed near the apex that touches the line of sight. It is dictated by the tall sight height.

-TL

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Is this different from simple right/left eye dominance hard-wired into sighting especially for those who are accustomed to shutting the left eyelid (reverse if you are left dominant)?
 
I managed to train myself to shoot with both eyes open. The major difficulty to overcome is seeing 2 targets. Sometimes the "wrong target" is picked to put the sight on. With enough practice, somehow the target seen by the non-dominant eye disappears and replaced by peripheral awareness.

But I think phoria, what the op of the discussion was diagnosed of, is different. There isn't dual vision. The dominant eye just perceives the target differently when the non-dominant eye is covered. There wouldn't be a diagnosis if it was normal, I think.

-TL

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that's why i choose to adjust out the parallax on my optics.

i have owned scopes that didn't have adjustment, and for speed, that's better if quick is more important than accurate.

for long range and small groups, accurate is more important than speed.

and yes i have forgotten to adjust parallax out and missed the mark. kinda gives one a case of jackass knoggen. but we get over that pretty quickly anyway.

at my age and poor vision, non-scoped percision shots are limited to about 50 yards. that's why all my long guns have scopes. my ar15 is the only thing that i run with irons + red-dot & flip to the side magnifier. but i have quick detach scope dedicated to it also, just not always on it.
 
I used to feel that parallax at close range didn’t matter so much… until I crossed paths with a particularly aggressive skunk; parallax got the better of me and the skunk won the matchup.
 
It is a bit difficult to visualize, but here is my understanding.

The scope forms an image of the target at certain focal plane. When the focal plane coincides with the reticle, there is no parallax. Say the shooter's eye shifts to the left by a small distance. He still focuses on the reticle. His line of sight is now deviating from the scope's axis by a small angle A.

No problem with zero parallax. The reticle is always on target. With parallax, however, there is distance between the target image and reticle. With angle A, the image remains the same, but the reticle appears to move, the direction of which depends on the target distance. It moves with the eye when the distance is less than the scope's parallax setting, and the other way otherwise.

If the shooter chooses to realign the reticle with the target, the poi will be off. The amount in moa is the same as angle A, if the scope has 1x magnification. The error in moa actually decreases at higher magnification.

Now it is all about angle A. Parallax will become a non-issue if angle A is very small. But how?

-TL

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you are back to the sizors; angle A is the amount the handles are apart, the pivot is the retical + parallax the cutting points are the point of aim and point of impact.
 
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