Bullet goes to sleep mode

[Ned Ludd]

Actually, a number of us *have* spent an unreasonable amount of time reading on this particular topic. The question isn't whether the phenomenon (bullet stabilizing as it gets further down range) happens, its whether it actually serves as a justifiable excuse for bigger groups near vs far. Everything I've read indicates that the amount of 'wobble' is not enough to account physically for the discrepancy in group sizes; scope parallax or simply shooter error (focusing too much on the group, not the aiming point at closer distances where they can actually see the bullet holes) are much more likely.

This is it in a nutshell. No one is arguing whether people have observed this phenomenon, or at least whether they believe they have. I have no doubt whatsoever that some folks have shot groups with smaller angular dispersion at longer distances than at a shorter distance like 100 yd. It's the cause that's in dispute. As has been well-documented by ballisticians like Robert McCoy and Bryan Litz, epicyclic swerve absolutely occurs. Unfortunately, any shot displacement caused by this yaw/pitch effect early in the bullet's flight isn't nearly enough to account for the discrepancies in angular as have been reported. Yes, it happens, but the effect dampens out in a relatively short distance and, according to experts, would have a maximum affect on group spread of well under one caliber.

On the other hand, parallax error goes up significantly as distance decreases, particularly from 100 yd in. Due to another debate on this very topic, some time ago I found a very thorough mathematical analysis of parallax error. Using the equations it contained, I made a plot of maximal parallax error versus distance out to 1000 yd. I can't find the graph or I would have posted it here. It took quite a bit of time to generate it and I'm not energetic enough to reproduce it right now. However, anyone wishing to do it themselves is welcome. What you'll find is that parallax error goes up dramatically at shorter distances. What that means in practical terms is that if your scope parallax setting isn't spot on, or your head moves the tiniest little fraction, it will open up your groups significantly more at distances of 100 yd or less than it will at 200-300 yd or farther. I think that is by far the most likely explanation for this phenomenon. It's also an explanation that doesn't require a significant re-write of the laws of physics .

 

[mike a]

It's not a great rifle but it holds 1/2 moa. Except at 100 yards. Really! I get 3/4 " at 100 and 1" at 200 and 1/2 moa from there to 500. Not just a few groups but many. Is there any real tested evidence for this. Even though I see with my own eyes it's hard to except.

Hi guys & girls, OP here. Ok, I got it. WOW that was simple. Jeez.

 

[BoydAllen]

On parallax: There is nothing very mysterious there. You can easily see if you have it. One way to know that you have a problem that requires a little adjustment, is if your side focus. or objective adjustment for sharpest target image gives you any amount of parallax. This is easy to fix. Otherwise, if peak target sharpness and absolutely zero parallax occur at the same point of adjustment, then your eyepiece is perfectly focused in the plane of the reticle, and no matter what distance you are shooting at, if you adjust so that your target is its sharpest, you will have no parallax.

 

[mike a]

On parallax: There is nothing very mysterious there. You can easily see if you have it. One way to know that you have a problem that requires a little adjustment, is if your side focus. or objective adjustment for sharpest target image gives you any amount of parallax. This is easy to fix. Otherwise, if peak target sharpness and absolutely zero parallax occur at the same point of adjustment, then your eyepiece is perfectly focused in the plane of the reticle, and no matter what distance you are shooting at, if you adjust so that your target is its sharpest, you will have no parallax.

Boyd, I thought I was done with this thread but you got me thinking. Off the subject of my VX3 w/AO. I have a VX2 3x9x40 non AO on a 308. So here's my question. If I adjust my focus (ocular) to sharpest at 500 would it reduce paralex. Might have to play with it a bit but isn't an AO just a focus fine tuner? I've never though about this. Thanks Mike A

 

[dkhunt14]

This is it in a nutshell. No one is arguing whether people have observed this phenomenon, or at least whether they believe they have. I have no doubt whatsoever that some folks have shot groups with smaller angular dispersion at longer distances than at a shorter distance like 100 yd. It's the cause that's in dispute. As has been well-documented by ballisticians like Robert McCoy and Bryan Litz, epicyclic swerve absolutely occurs. Unfortunately, any shot displacement caused by this yaw/pitch effect early in the bullet's flight isn't nearly enough to account for the discrepancies in angular as have been reported. Yes, it happens, but the effect dampens out in a relatively short distance and, according to experts, would have a maximum affect on group spread of well under one caliber.

On the other hand, parallax error goes up significantly as distance decreases, particularly from 100 yd in. Due to another debate on this very topic, some time ago I found a very thorough mathematical analysis of parallax error. Using the equations it contained, I made a plot of maximal parallax error versus distance out to 1000 yd. I can't find the graph or I would have posted it here. It took quite a bit of time to generate it and I'm not energetic enough to reproduce it right now. However, anyone wishing to do it themselves is welcome. What you'll find is that parallax error goes up dramatically at shorter distances. What that means in practical terms is that if your scope parallax setting isn't spot on, or your head moves the tiniest little fraction, it will open up your groups significantly more at distances of 100 yd or less than it will at 200-300 yd or farther. I think that is by far the most likely explanation for this phenomenon. It's also an explanation that doesn't require a significant re-write of the laws of physics .

If you shoot a heavy gun on rails this takes parallax out of the picture. The scope is only used to get you in the center of the target. Then you just feed and shoot. A lot of people don't even look through there scope. Joe Salt ought to know that. His wife never looked. Matt

 

[Ned Ludd]

If you shoot a heavy gun on rails this takes parallax out of the picture. The scope is only used to get you in the center of the target. Then you just feed and shoot. A lot of people don't even look through there scope. Joe Salt ought to know that. His wife never looked. Matt

Agreed, but how many reporting larger angular dispersion at closer range are actually shooting their gun on rails?

 

[Homerange]

Agreed, but how many reporting larger angular dispersion at closer range are actually shooting their gun on rails?

Would that not suggest their loads are producing stable bullet flight?

 

[dkhunt14]

Agreed, but how many reporting larger angular dispersion at closer range are actually shooting their gun on rails?

Almost every heavy gun is 1000 yard BR is that way. Lots of guys saw it. Matt

 

[memilanuk]

Almost every heavy gun is 1000 yard BR is that way. Lots of guys saw it. Matt

...and yet not one took up the gauntlet on Bryan Litz's challenge earlier. Shoulda been easy money for them.

 

[savagedasher]

Powder burn rate has alot to do with putting a bullet asleep. With a tuner you can see it happen at shorter yardage. Larry

 

[Ned Ludd]

If it's all that common of an occurrence, then by all means at least one of the shooters should invite Bryan Litz out to a match. Then they could demonstrate it to him firsthand, since he's been asking for anyone to do that for some time now. Seems rather odd no one has taken him up on his request as yet.

 

[Raythemanroe]

If it's all that common of an occurrence, then by all means at least one of the shooters should invite Bryan Litz out to a match. Then they could demonstrate it to him firsthand, since he's been asking for anyone to do that for some time now. Seems rather odd no one has taken him up on his request as yet.

He has been invited multiple times


Ray

 

[lbran]

He has been invited multiple times


Ray

the one who wrote the readin, wrote the readin right don't ya see!!!! from [ festus on gunsmoke ] lol

 

[chkunz]

This subject has been beat to death, some folks have learned something and some have not, some folks have contributed something useful and some have not but overall the thread has been positive. I will offer one more point for those who are still reading. Most folks measure groups by extreme spread, this is easy but it has the disadvantage of only evaluating two shots from the group and can be misleading in analysis such as has been discussed on this thread. There are several other ways of evaluating groups, mean radius being one other method. The advantage of mean radius is that all shots in the group are evaluated equally and the results are more meaningful. The disadvantage is that it takes more effort to calculate mean radius than it does extreme spread and many folks are turned off by the math. I will offer that if the cases sited herein where groups MOA improve with distance were calculate with mean radius the results may be different.

 

[Ringostar]

What if I don't want my bullets to take a nap? I might prefer them to stay awake, so they can see their way to the center of the target. I've learned the hard way to always adjust my parallax.

 

[savagedasher]

This subject has been beat to death, some folks have learned something and some have not, some folks have contributed something useful and some have not but overall the thread has been positive. I will offer one more point for those who are still reading. Most folks measure groups by extreme spread, this is easy but it has the disadvantage of only evaluating two shots from the group and can be misleading in analysis such as has been discussed on this thread. There are several other ways of evaluating groups, mean radius being one other method. The advantage of mean radius is that all shots in the group are evaluated equally and the results are more meaningful. The disadvantage is that it takes more effort to calculate mean radius than it does extreme spread and many folks are turned off by the math. I will offer that if the cases sited herein where groups MOA improve with distance were calculate with mean radius the results may be different.

Putting a bullet asleep you only use one shot but 5 or more . Paper tear is what you look at.
Archers have done it for years.
Larry

 

[Joe Salt]

gstaylorg the last time Brian Litz was in williamsport was 16 years ago He was in both my relays and he didn't make out so well! I've shot against the best shooters in the world, sometimes they win sometimes I win. I managed to get Sebastian Lambang of Seb Rests to come to this years World Open. Lucky I guess. Brian is only in Michigan not half way around the world. He knows the way he shoots at Reade range in PA. But he shoots different discipline, 1000 Yard Benchrest is to easy.

Joe Salt

 

[Ned Ludd]

 

[Webster]

It's not a great rifle but it holds 1/2 moa. Except at 100 yards. Really! I get 3/4 " at 100 and 1" at 200 and 1/2 moa from there to 500. Not just a few groups but many. Is there any real tested evidence for this. Even though I see with my own eyes it's hard to except.

What happens when a bullet has a jacket 1/100,00 or 1/1,000,000 of an inch thicker on one side or 1,000,000 th. of a grain heaver on one side and you spin it at 300,000 RPM? How about the opposite. If I shoot an 85 Gr bullet in my 6BR 14 twist I get a group of about 12". I think it's common knowledge you can get keyholes in the target from a bullet that isn't spun fast enough. If a bullet doesn't go to sleep how can it get unstable to start with? Is the implication that if it isn't a perfect bullet and it's spun at the proper rate it will never yaw. Is this possible?

 

[Raythemanroe]