MOA at one distance,but not others.

[Mikecr]

Richard's right.
The whole going to sleep notions have been used to explain more than existing basis.

I personally have the shrinking MOA issue -with all my guns. But I'm convinced it's parallax from my glasses lens(that tiny part off-prescription that I'm forced to aim through).
I'm also convinced that parallax is far easier to set at distance than up close.
This, because our brains adjust vision, painting a picture that's clear enough -if it can. And 'good enough' is a lot easier of a brain adjustment up close.
At distance your focus is more sharply right or wrong, and the brain can't adjust diddly for it..

 

[Bart B]

I personally have the shrinking MOA issue -with all my guns. But I'm convinced it's parallax from my glasses lens(that tiny part off-prescription that I'm forced to aim through).

Your glasses don't have anything to do with parallax.

Parallax is caused by the error in a scope's objective lens system not focusing the target exactly on the reticule. That error's not effected by the lenses behind the reticule (scope's eyepiece lens and your spectacles, if worn) which combine to allow your eye to focus sharply on either the reticule or target image if parallax is present. Where you eye's focused with the lenses between it and the reticule have no effect on where the target image is focused; on or off the reticule. If your optical prescription's a quarter diopter off, that doesn't effect the relative position between the reticule and target image plane; all it does is make either one sharper or fuzzier. Adjusting the scope's eyepiece changes its effective diopter with your glasses just like the right eyepiece on a pair of binoculars changes the effective diopter of your right eye's lens in your glasses. That eyepiece on your binoculars is marked in + and - diopter values. Too bad scope eyepieces aren't marked the same as they perform exactly the same optical function.

I'm also convinced that parallax is far easier to set at distance than up close.

Optically impossible. That's 'cause the range band of apparent perfect focus on the target and apparent zero parallax gets greater as target range increases. The same optical formulas can be used to calculate it as what's used to calculate depth of field (image sharpness) on camera lenses. It's the apparent depth of field your rifle scope has that allows one to get accurate focus to eliminate parallax at a given range. Focused perfectly at 500 yards, a rifle scope with an objective lens group focal length of 250 mm (typical for a 10X scope) and a 50mm diameter objective lens will have a range band of sharp focus about 200 times greater than when it's focused at 50 yards. Therefore, it's a lot harder to get absolute zero parallax at the longer ranges than short ones.

Look at the distance valuse on a telephoto camera lens. Rotating the lens barrel 1/8 inch may change focus from 60 inchs to 61 inches. But when the lens is set at 1000 yards (infinity?), rotating the lens barrel 1/8 inch may change focus distance to 100 feet. How far is it from 100 feet to 1000 yards?

 

[Mikecr]

Bart, I agree that my notions conflict with math.
But the shrinking moa of shooting IS real, and consistent, for those who are dealing with it and no math predicts it so far.

So given that NOBODY has actually solved this mystery, I'm going to contend until so that it's caused by our brain's adjustment under conditions yet to be identified.
Regardless of math/optical precision, at 25x+, it seems(to me) far easier to 'think' I hold images focused while off-plane at close ranges, than at long ranges.

I know there is lash & inaccuracy in side focus markings, but if I set/reset focus at 500yds 5-6 times, that knob comes to a very consistent position. If I do the same at 100yds, the side focus setting ends up with a good bit of variance.

If I took a 30br well tuned to shoot in the 1s, I would struggle in perfect conditions to produce .25" groups with it at 100yds. I wouldn't bet a bacon cheeseburger on 1/2" at 200yds. But I would take the bet, for 3/8", at 300yds.

 

[Joe King]

About my comments regarding a 1/2 MOA system at 100 won't be a 1/2 MOA system at 1000 yards. . . . So, what qualifications and equipment must I have to prove anything about that?

Please let me know what you think my qualifications are and what equipment I've got and I'll see if they match what reality is.

And note I've already mentioned one exception stating one rifle known world wide in long range competition that shoots better at the longer ranges than the shorter ones. I didn't mention the M14 US service rifle that does the same thing as the SMLE's but to a lesser degree. Therefore, I already know that "some" rifles do shoot better at longer ranges compared to shorter ones.

Well if your proposing that your as qualified as say I dunno the military to test and research these things. hey gotta have our resident genius right? back to the ignore list you go

 

[Joe King]

That's a great article. But, you failed to read or understand his conclusion.

Bryan pretty much tried everything he could to mathematically force Epicyclic Swerve to explain the phenomenon. In the end, he stated that it just isn't a big enough factor to explain even as much as a caliber's worth of swerve.

Paralax, marksmanship, and statistical sampling error are the most common causes.

-- richard

I was referring to the 1st paragraph and yes I do understand the whole article, Brain is pretty damned brilliant that way, but my point is, is that there's still no factual scientific explanation as to why this happens, why it happens with some rifle and not others. There's some very very go theories about it, but if guys like Brian have such a hard time pinning it down............

 

[Joe King]

Bart, I agree that my notions conflict with math.
But the shrinking moa of shooting IS real, and consistent, for those who are dealing with it and no math predicts it so far.

So given that NOBODY has actually solved this mystery, I'm going to contend until so that it's caused by our brain's adjustment under conditions yet to be identified.
Regardless of math/optical precision, at 25x+, it seems(to me) far easier to 'think' I hold images focused while off-plane at close ranges, than at long ranges.

I know there is lash & inaccuracy in side focus markings, but if I set/reset focus at 500yds 5-6 times, that knob comes to a very consistent position. If I do the same at 100yds, the side focus setting ends up with a good bit of variance.

If I took a 30br well tuned to shoot in the 1s, I would struggle in perfect conditions to produce .25" groups with it at 100yds. I wouldn't bet a bacon cheeseburger on 1/2" at 200yds. But I would take the bet, for 3/8", at 300yds.

That maybe truer than any of us care to admit, ask a high power silhouette shooter which targets they drop the most points on. lol

 

[rscott5028]

I'm too ignorant to argue the optical math. But, I believe paralax is an issue for some shooters and their scopes at times. If paralax is eliminated at long range and prevalent at close range, groups will likely be better at long range barring perfect cheek weld. It's doubtful that this is the case every time someone experiences better groups at long range.

There are many theories as to if/why some rifles may consistently and repeatably improve their MOA accuracy at increasing distances.

But, I have yet to see a statistically valid, scientific experiement that proves that the phenomenon actually exits. ...much less, proof as to the why part.

-- richard

 

[rscott5028]

I was referring to the 1st paragraph and yes I do understand the whole article, Brain is pretty damned brilliant that way, but my point is, is that there's still no factual scientific explanation as to why this happens, why it happens with some rifle and not others. There's some very very go theories about it, but if guys like Brian have such a hard time pinning it down............

I have a lot of respect for Brian Litz (bsl135) as do many here.

He's weighed in on this topic many times.

-- richard

 

[Bart B]

Well if your proposing that your as qualified as say I dunno the military to test and research these things. hey gotta have our resident genius right? back to the ignore list you go

Does anybody reading this thread understand that?

That doesn't make any sense to me at all. Please keep me off your "ignore list" until you explain again using different words.

 

[Bart B]

but my point is, is that there's still no factual scientific explanation as to why this happens, why it happens with some rifle and not others. There's some very very go theories about it, but if guys like Brian have such a hard time pinning it down............

Scientific Explanations that apply to vertical shot stringing differences at different ranges.

Barrel Tuner Analysis -- FEA Dynamic Analysis of Esten's Rifle with/without a Tuner.

FEA Barrel Pressure Analysis on a 6PPC Rifle Barrel

Finite Element Analysis -- Dynamic Analysis of a Light Rifle with/without a tuner.

As far as both vertical and horizontal shot stringing, I've yet to see anyones' explanation as to how a bullet (spin balanced, stabilized or not) at the outside edge of an imaginary group at 100 yards knows how to change its direction to strike close to group center at any further range. And then acutally makes that direction change without any external force applied.

I don't know of anyone who's done firing tests where each bullet goes through an acoustic target at each range. Then each bullet's position in each aerial group would be plotted. Any group size angular change between ranges would be accurately measured. To me, this is the best test/experiment to see how group's subtended angles change with range. Sierra Bullets may have done such tests, but I've not seen any results.

 

[RTK]

I've yet to see anyones' explanation as to how a bullet (spin balanced, stabilized or not) at the outside edge of an imaginary group at 100 yards knows how to change its direction to strike close to group center at any further range. And then acutally makes that direction change without any external force applied.

.

Read my post again about a guy that read some military test and it will answer that question. It is not the fact that it is changing path or moving closer, just not deviating anymore at distance..
Example,,,, IF a bullet travels in say, a 1 inch elliptical path at 100 yards, that's 1 MOA, but at 200 yards that 1 inch elliptical path is 1/2MOA and so on and so forth

 

[rscott5028]

[...]I've yet to see anyones' explanation as to how a bullet (spin balanced, stabilized or not) at the outside edge of an imaginary group at 100 yards knows how to change its direction to strike close to group center at any further range. And then acutally makes that direction change without any external force applied.[...]

I try to keep an open mind.

But, I'm still waiting for that explanation as well.

-- richard

 

[rscott5028]

Read my post again about a guy that read some military test and it will answer that question. It is not the fact that it is changing path or moving closer, just not deviating anymore at distance..
Example,,,, IF a bullet travels in say, a 1 inch elliptical path at 100 yards, that's 1 MOA, but at 200 yards that 1 inch elliptical path is 1/2MOA and so on and so forth

Please get the guy to post the millitary test report.

Bullets don't/can't travel in a 1/2 MOA elliptical path.

Bryan Litz proved that long ago.

-- richard

 

[barnesuser28]

I'm getting a headache from reading this thread.