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Thread: Groups at 25 yards.

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    Default Groups at 25 yards.

    Now that the New Year is upon us, and I've wished you all a Happy New Year, though unbeknownst to you.

    I'm wondering IF the bullet, (Hunting Rifle Cartridge, loads), is fully stabilized at 25 yards.

    My reason for wondering, and this question, is that when sighting in a scope, I've sometimes noticed a disappointing group.

    But, on finalizing at 100 yards, a much better group transmitting to better than the 25 yard group x 4.

    Whaddayya think/know?

    Thanks.

    Smitty of the North, Version 2015. 0.
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    Rifle bullets usually are not fully stable until quite a bit further out than 25yds but I don't think that is what accounts for your issue. Most hunting rifle scopes are parallax adjusted for 100/150yds. Sandbag your gun and look through the scope moving your eye left, right, up and down at 25yds checking crosshair movement on the target. Repeat at 100yds. Normally the movement will be relatively greater at 25 yds than 100 thus making your cheek weld much more important at 25 than 100. On an OA scope this can be adjusted out. I think this accounts for a lot of the groups being relatively worse at close range than longer ranges.

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    Maybe so.

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    Quote Originally Posted by Smitty of the North View Post
    Maybe so.

    SOTN
    What-a-ya mean maybe so. Heck when a bullet comes out the barrel it is fishtailing like the neighbor kid coming around the corner on ice in his old mans car. He's either got it straightened out in a half a block or he keyholes through someones house. House come you always come up with these head scratching notions anywho? I'm going to go ahead and agree with rbuck351 cuz I've done figured out that he has been around the horn in regards to guns and what it is that makes em go bang and stuff! He's learned me a plenty!

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    Quote Originally Posted by elmerkeithclone View Post
    What-a-ya mean maybe so. Heck when a bullet comes out the barrel it is fishtailing like the neighbor kid coming around the corner on ice in his old mans car. He's either got it straightened out in a half a block or he keyholes through someones house. House come you always come up with these head scratching notions anywho? I'm going to go ahead and agree with rbuck351 cuz I've done figured out that he has been around the horn in regards to guns and what it is that makes em go bang and stuff! He's learned me a plenty!
    Let's just say, that he's "Probably Right".

    You're "Probably Right" too, but I won't know until I find out what you actually think.

    I'm aware of the Parallax thingy, I jist have trouble remembering how to spell it, but I've always wondered about the stability thing. To overcome the Parallax problem which is that the scope parallax is set for a longer range than 25 yards, I understand that you gotta make sure you are centering your vision in the scope each time.

    I have one scope that has an adjustable AO. I should do some testing with it.

    BUT WHY KNOCK MYSELF OUT, when I've got YOU and RBUCK?

    I think it's time for my nap.

    Smitty of the North
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  6. #6

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    The best answer that I can give you based on what I know is that many a time I have shot better groups at 100 yards than at 25 with same set up. There is for sure something in the thrust of the bullet from the pressure build up from the burning powder/gases that sets the bullet into motion in a less than stable state. The purpose of the rifling is to correct that unstable state. My guess is that without rifling the bullet would fly like a knuckle ball. The bullet in most cases has only made a couple revolutions by the time it exits the rifling thus the sabalizing procedure has only just begun. Only once the bullet is outside the barrel spinning freely can it stabalize. I can't tell you what percentage of a second it takes for the spinning to fully
    stabalize but do know that the bullet has already traveled 100 yards in one tenth of a second.

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    Quote Originally Posted by elmerkeithclone View Post
    The best answer that I can give you based on what I know is that many a time I have shot better groups at 100 yards than at 25 with same set up. There is for sure something in the thrust of the bullet from the pressure build up from the burning powder/gases that sets the bullet into motion in a less than stable state. The purpose of the rifling is to correct that unstable state. My guess is that without rifling the bullet would fly like a knuckle ball. The bullet in most cases has only made a couple revolutions by the time it exits the rifling thus the sabalizing procedure has only just begun. Only once the bullet is outside the barrel spinning freely can it stabalize. I can't tell you what percentage of a second it takes for the spinning to fully
    stabalize but do know that the bullet has already traveled 100 yards in one tenth of a second.
    Regardless of the number of revolutions the bullet has achieved before exiting the barrel, the bullet is traveling at the highest rpm that it's going to travel upon exiting the barrel is it not? Then mustn't the bullet be stable upon exit if it's EVER going to be stable, since revolving is what keeps it stable? Interesting questions indeed...


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    Quote Originally Posted by limon32 View Post
    Regardless of the number of revolutions the bullet has achieved before exiting the barrel, the bullet is traveling at the highest rpm that it's going to travel upon exiting the barrel is it not? Then mustn't the bullet be stable upon exit if it's EVER going to be stable, since revolving is what keeps it stable? Interesting questions indeed...


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    I dunno. I understand that the spin doesn't slow much throughout.

    And, that the bullet does settle down, (Go to sleep, or become more stable, (1K BR theory) somewhere downrange.

    I could accept that, but if it's true, is there a diff betwixt 0 and 25 yards?

    Smitty of the North
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    Quote Originally Posted by Smitty of the North View Post
    I dunno. I understand that the spin doesn't slow much throughout.

    And, that the bullet does settle down, (Go to sleep, or become more stable, (1K BR theory) somewhere downrange.

    I could accept that, but if it's true, is there a diff betwixt 0 and 25 yards?

    Smitty of the North
    My guess, and it's just that, is that the bullet is most stable as it leaves the barrel and only gets worse from there.

    I've done a bit of reading on bullets "going to sleep" and as best as I can interpret it, that theory is unproven.

    I believe the poster who referenced the effects of parallax is on a more probable trail, it's also the reason target shooting types want their sights as far apart as possible.


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    Quote Originally Posted by limon32 View Post
    My guess, and it's just that, is that the bullet is most stable as it leaves the barrel and only gets worse from there.

    I've done a bit of reading on bullets "going to sleep" and as best as I can interpret it, that theory is unproven.

    I believe the poster who referenced the effects of parallax is on a more probable trail, it's also the reason target shooting types want their sights as far apart as possible.


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    Thanks. I will cogitate on that.

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  11. #11

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    Smitty:

    If you have a copy of the Sierra manual, you might want to read (reread?) the section on exterior ballastics.

    Just a thought.

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    The bullet is at it's least stability just as it leaves the barrel. I beleive this to be caused by the high pressure gases shoving the bullet to one side or another just as it leaves the barrel. There is no such thing as a perfect bullet base or a perfect crown. Because of that the gas is going to escape a tiny bit quicker in one spot causing the base to get kicked sideways a tiny bit. Depending on spin and amount of base deflection, the bullet will get kicked to one side more or less from shot to shot and some will stabilize quicker or slower than the next. Most folks seem to believe it takes around 100yds or more to fully stabilize. However if it's shooting 1" or bigger at 25yds, and say only 1 1/4" to 1 1/2" at 100, I'm thinking it's probably more than just bullet stability but stability is probably part of the equation. Please don't take these thoughts to be gospel as I will be the first to say these are just my thoughts on stability and parallax issues

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    The 'standard' range to 'battle zero' an M16 is 25 yards, and yes I know this is not a hunting rifle for most people. I use 25 yards as a 'starting' point and just about all of my hunting rifles will put 3-5 shots very close together at that range. Then I move to 100 yards and make adjustments as needed from there. For some 'long range' bullets, they tend not to stabilize until they get out there quite a distance. What I have found is that some rifles do not like curtain bullets and no matter what one does, they will not shoot well. As an example, the wife's Savage 338WM really likes the Barnes 200 bullet, where as my Winchester MD 70 would not group them at all, but really like the 225 Barnes bullets.

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    I say we all pool our money on a very high speed camera and take some pictures of a bullet leaving a barrel!

    I've read a lot of discussion on the subject but I've never found anything that seemed very definitive, I'm probably just looking in the wrong places though!


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    Quote Originally Posted by 7STW View Post
    Smitty:

    If you have a copy of the Sierra manual, you might want to read (reread?) the section on exterior ballastics.

    Just a thought.
    Y'OK
    Thanks
    Smitty
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    I admit that I might be missing something, but if (for whatever reason at all) a projectile is deviating from the point of aim at 25yds, it will not and cannot self-correct and turn back to get on the correct course at some further distance--unless it has self-correcting fins, thrusters, etc ... like an airplane or a rocket. If bullets all are spreading out from the line of sight at 25 yards, they can't turn back toward that axis or even turn to be more parallel to it because the bullet doesn't "know" where it is or where to go. Even if it becomes more stable, it cannot correct for the initial, erroneous flight path. Thus, if it becomes more stable at 25yds, perhaps it could stop curving away from it's current flight path, but, at best, it would continue along that incorrect flight path, even if it did so in a more-stable and straight line.

    Unless I'm missing something pretty dramatic, I just don't see how a bullet can correct even if it becomes more stable.

    I vote for the scope parallax thing or something along those lines.

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    Quote Originally Posted by MarineHawk View Post
    I admit that I might be missing something, but if (for whatever reason at all) a projectile is deviating from the point of aim at 25yds, it will not and cannot self-correct and turn back to get on the correct course at some further distance--unless it has self-correcting fins, thrusters, etc ... like an airplane or a rocket. If bullets all are spreading out from the line of sight at 25 yards, they can't turn back toward that axis or even turn to be more parallel to it because the bullet doesn't "know" where it is or where to go. Even if it becomes more stable, it cannot correct for the initial, erroneous flight path. Thus, if it becomes more stable at 25yds, perhaps it could stop curving away from it's current flight path, but, at best, it would continue along that incorrect flight path, even if it did so in a more-stable and straight line.

    Unless I'm missing something pretty dramatic, I just don't see how a bullet can correct even if it becomes more stable.

    I vote for the scope parallax thing or something along those lines.
    Well, we can all miss things that haven't been enumerated, whether it seems dramatic or not.

    I yam jist an ignernt hillbilly with little education, and not really qualified to get into the scientic.

    I'm not suggesting "self correction", but Say the bullet is Yawing and the Yawing settles down and it doesn't YAW as much?

    Beyond all that, I can see where a bullet at a particular range, could consistently land in more the same place, after goin through what it goes through on the way.

    I've always maintained that ballistics is largely an experimental science. You can't predict, or explain what happens with any great certainty. You can, only theorize after the fact, because there are apparently effects that are not a part of the usual equation.

    Smitty of the North
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    Quote Originally Posted by MarineHawk View Post
    I admit that I might be missing something, but if (for whatever reason at all) a projectile is deviating from the point of aim at 25yds, it will not and cannot self-correct and turn back to get on the correct course at some further distance--unless it has self-correcting fins, thrusters, etc ... like an airplane or a rocket. If bullets all are spreading out from the line of sight at 25 yards, they can't turn back toward that axis or even turn to be more parallel to it because the bullet doesn't "know" where it is or where to go. Even if it becomes more stable, it cannot correct for the initial, erroneous flight path. Thus, if it becomes more stable at 25yds, perhaps it could stop curving away from it's current flight path, but, at best, it would continue along that incorrect flight path, even if it did so in a more-stable and straight line.

    Unless I'm missing something pretty dramatic, I just don't see how a bullet can correct even if it becomes more stable.

    I vote for the scope parallax thing or something along those lines.
    That how think about the stabilization, if spin stabilizes a bullet, and spin is imparted on forward motion of the bullet through the barrel, how can it be more stable when it's spinning slower at all points after leaving the barrel?


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    Premium Member MarineHawk's Avatar
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    Quote Originally Posted by Smitty of the North View Post
    Well, we can all miss things that haven't been enumerated, whether it seems dramatic or not.

    I yam jist an ignernt hillbilly with little education, and not really qualified to get into the scientic.

    I'm not suggesting "self correction", but Say the bullet is Yawing and the Yawing settles down and it doesn't YAW as much?

    Beyond all that, I can see where a bullet at a particular range, could consistently land in more the same place, after goin through what it goes through on the way.

    I've always maintained that ballistics is largely an experimental science. You can't predict, or explain what happens with any great certainty. You can, only theorize after the fact, because there are apparently effects that are not a part of the usual equation.

    Smitty of the North
    I'd go with the sense-making optical theory over the self-correcting post-yaw bullet that was going on the wrong course and, after yawing ends, it starts to turn back (out of all possible 360 degrees) toward the line of sight where the scope is pointing. That's just my assessment.

    I've never heard "jist an ignernt hillbilly" before use words and phrases like "enumerated," and "I've always maintained that ballistics is largely an experimental science," etc ... An odd combination.

    I personally think you are very smart, but I wonder why you pretend to be something different to be more homey and folksy.

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    Quote Originally Posted by limon32 View Post
    That how think about the stabilization, if spin stabilizes a bullet, and spin is imparted on forward motion of the bullet through the barrel, how can it be more stable when it's spinning slower at all points after leaving the barrel?


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    I tend to agree, but I just don't feel I'm on solid enough ground on this one. Regardless, I just don't see how a bullet that has (for whatever reason) started moving away from the line of sight, could "stabilize" and then turn back toward the intended target -- as opposed to continuing to move in the direction it's going at 25 yds.

    There are only a few material forces on a bullet after it leaves the muzzle: (i) gravity (works only in one direction--down); (ii) axial wind resistance (works only in direction -- slows the bullet down); (iii) changes in air pressure (probably not relevant); and (iv) lateral wind (moves the bullet in the direction of the wind). There's really nothing else. So, if a bullet is 0.1 degrees to the right of the direction the barrel was pointing for whatever reason for the first 25yds: even if the factor that started pushing it in that direction (including yawing) goes away, the bullet will continue to move in that direction subject to the forces of gravity, wind resistance, and wind drift--none of which could magically turn the bullet back toward the place that the scope was originally pointing on any consistent basis, as opposed to an occasional random incident.

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