.22 Headspace (or does it matter....)

[_Shorty]

Still not true. There's a very good reason why no one reads about "50 yard barrels" or "100 yard barrels". It's because it's not a thing.

*ahem* 50-yard barrel



Sorry, Glenn, but barrels vibrate during firing just like a tuning fork. A barrel is a cantilevered beam just like a tuning fork. Make the barrel fatter and shorter and you increase the frequency while decreasing the amplitude. In other words, it vibrates back and forth more often in a given time, but moves a smaller distance in each cycle. Make the barrel skinnier and longer and you decrease the frequency while increasing the amplitude. In other words, it vibrates back and forth less often in a given time, but moves a larger distance in each cycle. The more you decrease the amplitude the less influence the barrel has and the more influence the load has, where a perfectly unmovable barrel would be 100% dependent on muzzle velocity. With that unmovable barrel the shots would land exactly where MV dictates, every single time, barring wind. Barrels moving during firing are what make it possible to tune them. Barrels moving during firing are what make it possible to tune centrefire loads. In both cases you are influencing where in the vibrational cycle the bullets exit. Here's how this barrel behaves versus a reverse taper barrel that used to be very popular in the 50-yard benchrest world for many years.



Notice the red/blue lines corresponding to this barrel rise more slowly than the green/green lines corresponding to a reverse taper barrel. Both are intended for 50-yard shooting. Without a tuner the reverse taper shows a 0.12" vertical spread for a 1035 fps shot and a 1075 fps shot, but the two-flats barrel shows just about 0.04" of vertical with the same speed shots because it is has a lower vibrational frequency. Both are still not ideal for 50 yards and require tuners. They're both too fast for ideal 50-yard compensation. The reverse taper barrel being a fair bit faster than the two-flats barrel.

Adding a tuner of sufficient weight to the reverse taper barrel will slow it down and provide a better tune for 50 yards. Whether or not you can slow it down enough to fully compensate for that 0.12" of vertical before hitting the trough at the bottom of the cycle where it begins moving in the other direction is another matter. This is to the left of the red dotted line signifying the muzzle exit of the 1075 fps shot. So you don't want to slow it down too much, or involving that trough and direction change is a danger, which would hamper the precision on target.

With the two-flats barrel contour you have a much slower vibrational cycle combined with a greater amplitude. In other words, the time where it is moving only upwards has been increased. It is moving upwards for a longer period of time. The trough that exists for the other barrel the muzzle exit time doesn't even exist with this barrel. Its closest trough and direction change is a further 0.0004 seconds earlier. So it begins its upward swing a fair bit sooner in addition to swinging slower. And the result is there is a smaller amount of vertical to tune out. With 0.04" of vertical to tune out versus 0.12" you can see the two-flats barrel is closer to the ideal 50-yard tune. This also means the tuner it requires will be a fair bit lighter than the tuner required for the other barrel. The amount it needs to be slowed down is less, so less additional mass (the tuner) is required.

Something isn't wrong just because you don't understand it. An open mind can learn more things. The more one learns, the more one can understand. It might be better to ask questions about something you don't understand rather than being dismissive of it. None of us know everything. Some people know things we don't. And they usually don't mind sharing knowledge when asked about it.

 

[_Shorty]

And let's not forget Bill Calfee's sporter contour with similar goals. Found these pictures while looking for a picture of the once common reverse taper barrels. This used stepped diameters rather than a continual taper. Just another way of approaching the same end result. You might recognize the name Bill Calfee. He used to work on guns a little bit.

 

[Longstud]

Shorty. You’re obviously well versed in harmonics and physics. Just wondering why someone as knowledgeable never submits any targets to any of the various challenges? You’ve obviously experimented and tracked, charted and correlated many years of testing and experimentation. I have a hard time believing all of us rimfire fanatics wouldn’t love seeing what you can accomplish.

 

[Meroh]

*ahem* 50-yard barrel

View attachment 1004428View attachment 1004429View attachment 1004430View attachment 1004431View attachment 1004432

Sorry, Glenn, but barrels vibrate during firing just like a tuning fork. A barrel is a cantilevered beam just like a tuning fork. Make the barrel fatter and shorter and you increase the frequency while decreasing the amplitude. In other words, it vibrates back and forth more often in a given time, but moves a smaller distance in each cycle. Make the barrel skinnier and longer and you decrease the frequency while increasing the amplitude. In other words, it vibrates back and forth less often in a given time, but moves a larger distance in each cycle. The more you decrease the amplitude the less influence the barrel has and the more influence the load has, where a perfectly unmovable barrel would be 100% dependent on muzzle velocity. With that unmovable barrel the shots would land exactly where MV dictates, every single time, barring wind. Barrels moving during firing are what make it possible to tune them. Barrels moving during firing are what make it possible to tune centrefire loads. In both cases you are influencing where in the vibrational cycle the bullets exit. Here's how this barrel behaves versus a reverse taper barrel that used to be very popular in the 50-yard benchrest world for many years.

View attachment 1004447

Notice the red/blue lines corresponding to this barrel rise more slowly than the green/green lines corresponding to a reverse taper barrel. Both are intended for 50-yard shooting. Without a tuner the reverse taper shows a 0.12" vertical spread for a 1035 fps shot and a 1075 fps shot, but the two-flats barrel shows just about 0.04" of vertical with the same speed shots because it is has a lower vibrational frequency. Both are still not ideal for 50 yards and require tuners. They're both too fast for ideal 50-yard compensation. The reverse taper barrel being a fair bit faster than the two-flats barrel.

Adding a tuner of sufficient weight to the reverse taper barrel will slow it down and provide a better tune for 50 yards. Whether or not you can slow it down enough to fully compensate for that 0.12" of vertical before hitting the trough at the bottom of the cycle where it begins moving in the other direction is another matter. This is to the left of the red dotted line signifying the muzzle exit of the 1075 fps shot. So you don't want to slow it down too much, or involving that trough and direction change is a danger, which would hamper the precision on target.

With the two-flats barrel contour you have a much slower vibrational cycle combined with a greater amplitude. In other words, the time where it is moving only upwards has been increased. It is moving upwards for a longer period of time. The trough that exists for the other barrel the muzzle exit time doesn't even exist with this barrel. Its closest trough and direction change is a further 0.0004 seconds earlier. So it begins its upward swing a fair bit sooner in addition to swinging slower. And the result is there is a smaller amount of vertical to tune out. With 0.04" of vertical to tune out versus 0.12" you can see the two-flats barrel is closer to the ideal 50-yard tune. This also means the tuner it requires will be a fair bit lighter than the tuner required for the other barrel. The amount it needs to be slowed down is less, so less additional mass (the tuner) is required.

Something isn't wrong just because you don't understand it. An open mind can learn more things. The more one learns, the more one can understand. It might be better to ask questions about something you don't understand rather than being dismissive of it. None of us know everything. Some people know things we don't. And they usually don't mind sharing knowledge when asked about it.

Theoretics are one thing, reality is often another.

Good luck with that.

When we design an injection mold we do it based on theoretics and lessons learned. Theoretically, we should be able to throw it in a press and shoot a part perfectly first and every time after. In reality, we spend weeks or Months tuning and venting... and still have to troubleshoot daily to keep things running at optimum.

When I see a barrel with a "reverse taper, or a big "nob" on the muzzle with a slender profile about half way back, any vibration and whip will be slow, but magnified in amplitude. To my eye, that barrel will flop around like a limp schwantz.

 

[_Shorty]

Shorty. You’re obviously well versed in harmonics and physics. Just wondering why someone as knowledgeable never submits any targets to any of the various challenges? You’ve obviously experimented and tracked, charted and correlated many years of testing and experimentation. I have a hard time believing all of us rimfire fanatics wouldn’t love seeing what you can accomplish.

No reason, really, other than perhaps being soured on "postal matches" by the cheating in the old days of the postal matches we had here and on Rimfire Central. After that, a lot of us just stuck to real in-person matches. And I'm usually too busy with testing things at the range and/or getting ready for matches, or just practicing. My shooting time this year has unfortunately been extremely limited. I think I only made it out to two or three silhouette matches. I've got the itch, but just haven't been able to scratch it.

Theoretics are one thing, reality is often another.

Good luck with that.

When we design an injection mold we do it based on theoretics and lessons learned. Theoretically, we should be able to throw it in a press and shoot a part perfectly first and every time after. In reality, we spend weeks or Months tuning and venting... and still have to troubleshoot daily to keep things running at optimum.

When I see a barrel with a "reverse taper, or a big "nob" on the muzzle with a slender profile about half way back, any vibration and whip will be slow, but magnified in amplitude. To my eye, that barrel will flop around like a limp schwantz.

I had the two-flats barrel that Varmint Al designed built a few years ago, to his surprise and delight, as he never even built one. I took those pictures to post here just now. That's my actual benchrest barrel. It's not currently installed on the gun, but it usually lives on my Win52D bench gun. It shot fairly well, even with Eley Team, their round that's two steps below their top Tenex, as seen here in this stats screenshot for the accompanying target. If you're unfamiliar, a 2300 is just four dropped shots out of 25. A perfect score being 2500, with those four 50s ruining the day, hehe. If centred slightly better it is ideally a 2350 score, with one of those 50s being bumped up to a 100. That's what the stats screenshot means by "best." Actual score / best score if perfectly centred. This is one of the toughest targets around, as it is scored worst-edge. So you have to keep the entire bullet hole within the middle 1/2" bull to get a perfect score. That's not easy for 25 shots where you're also moving for every single shot.



I took it off the gun a little while back because I somehow missed when I first got it made that one of the dimensions wasn't to spec, so I wanted to get that corrected. And since I had that done I haven't picked up more good ammo to test, so it's just been sitting and waiting. But even though the thing was slightly off spec it was doing what it said on the tin. It was just very finicky about the tuner weight because the muzzle section was slightly too long, and as a result it was slightly too heavy. It wasn't so slow that it missed the intended slope of muzzle rise for 50 yards, but it was so close to it that I had to resort to using 3D-printed tuners that were so incredibly light that even variance in the plastic from one iteration to the next was enough to throw it off. Cutting the muzzle down so it actually met the intended spec should smarten it up and allow me to use a tuner that's a bit heavier to dial it in, and the more mass that's allowable in the tuner itself means the more forgiving that dialling in process should be. Larger tuner mass means less effect from its weight variance. These are but a fraction of the iterations to introduce tweaks here and there, and do-overs due to variance.



Now that the overlooked spec has been corrected it will require figuring out a good weight for the tuner and will have to be tuned all over again. But it should be an easier job, as I say, because the tuner mass will now be larger and thus not as finicky. But I still haven't found the time or the ammo to get out there for more testing since that job was done.

The graph I posted along with the barrel pictures shows that the movement for it is of a lower frequency and a larger amplitude than the reverse taper barrel. That's the whole point. Moving slower and in larger swings isn't a negative in this case. When you're shooting 50-yard benchrest you need the barrel to move slow enough to compensate for muzzle velocity variance according to the needs of 50 yards. I remember for 50 metres the figure is ~6 MOA per millisecond, which I remember because it is a nice round number. For 50 yards I think it is something like 4.7 MOA per millisecond, but I don't recall exactly, and that's just off the top of my head. Anyway, it is a number you can calculate for any distance just by using a ballistic calculator for two different round velocities. And the larger the amplitude, the longer it will remain moving in a single direction, making it easier to get all shots leaving during an upswing. A tuner's sole purpose is to slow a barrel down. That's all it does. And its adjustable nature allows you to dial in just the right speed for a given distance, providing it is of sufficient mass for a given barrel, and the barrel by itself is too fast for that distance. Step away from the two-flats, and the reverse taper, and stuff like Calfee's design, back to a more traditional taper or straight barrel and the muzzle swing is sped up. As you speed up the swing, if you can keep it to where there's an upswing for the average muzzle exit timing period, you push the tuning distance further and further away. If you can't keep muzzle exit timing within an upswing then things can get more squirrelly. Shots exiting during a downswing is the worst. Shots exiting randomly during an upswing or downswing is bad, but still better than all on a downswing. All shots exiting during an upswing is the best of the three situations. And the ideal is to have that upswing rate match the requirements for the distance at which you are shooting. The stiffer the barrel, the higher the frequency, and the lower the amplitude of those swings. That makes it more reliant on consistent MV, but can be a better compromise when one has to shoot at multiple or unplanned distances.

 

[grauhanen]

Shorty is insisting that all barrels shoot best at one distance only. It might be 50 yards, 100 yards, or something else. In other words Shorty says that every barrel is best used at a specific distance and that at other distances they are not effective.

Here's what is a fact. All .22LR accuracy performance decreases as distance increases. That means no barrel shoots better (MOA-wise) at longer distances than at shorter ones. Why is this a fact? Rimfire .22LR accuracy never improves with distance. One obvious cause is that no matter what .22LR match ammo is used, the effects of gravity increases with distance. (Same for wind if conditions are included.) Performance with .22LR always gets worse with distance. The ammo isn't consistent enough to produce consistent results as distances grows.

Unusual examples of the two-flats barrel or the Calfee example are not convincing arguments supporting the notion that all barrels are distance-specific. It's known that some barrels have been made with built-in tuners for disciplines where standard (removable) tuners are not permitted. These rifles are shot at 50 yards but they can also be used effectively at longer distances. Of course no rifle will shoot better at 100 than at 50. And certainly no .22 LR rifle shoots better at 200 than at 100.

No rifle maker -- Vudoo, RimX, Anschutz, Walther, FWB, Bleiker, Grünig + Elmiger or any other -- makes a model for 50 yards and a model for 100. Why? They don't exist. It's not a thing.

Shorty, give this a rest.

 

[_Shorty]

Shorty is insisting that all barrels shoot best at one distance only. It might be 50 yards, 100 yards, or something else. In other words Shorty says that every barrel is best used at a specific distance and that at other distances they are not effective.

Here's what is a fact. All .22LR accuracy performance decreases as distance increases. That means no barrel shoots better (MOA-wise) at longer distances than at shorter ones. Why is this a fact? Rimfire .22LR accuracy never improves with distance. One obvious cause is that no matter what .22LR match ammo is used, the effects of gravity increases with distance. (Same for wind if conditions are included.) Performance with .22LR always gets worse with distance. The ammo isn't consistent enough to produce consistent results as distances grows.

Unusual examples of the two-flats barrel or the Calfee example are not convincing arguments supporting the notion that all barrels are distance-specific. It's known that some barrels have been made with built-in tuners for disciplines where standard (removable) tuners are not permitted. These rifles are shot at 50 yards but they can also be used effectively at longer distances. Of course no rifle will shoot better at 100 than at 50. And certainly no .22 LR rifle shoots better at 200 than at 100.

No rifle maker -- Vudoo, RimX, Anschutz, Walther, FWB, Bleiker, Grünig + Elmiger or any other -- makes a model for 50 yards and a model for 100. Why? They don't exist. It's not a thing.

Shorty, give this a rest.

Again, you not understanding something doesn't make it wrong. I even gave you a very simple test to conduct to see for yourself whether you're correct or not. Go shoot groups at 10-yard increments starting as close as your scope allows and see for yourself what happens. But oh no. You'd rather continue speaking from ignorance. And I never said anything about barrels not being effective at other distances. You like to misconstrue things people say, paraphrase it with some odd twist, and then act as if it were a direct quote. Not sure where you picked up that tendency, but it is a strange one.

Your idea that it just continually gets worse from the muzzle forward is incorrect. Dispersion is best at one distance for a given barrel and a given ammo. Starting from the muzzle, dispersion increases until about halfway between the muzzle and that ideal distance. From about the halfway point until the ideal distance it begins decreasing again. Dispersion is at a minimum at that ideal distance. And once it passes that ideal distance it begins growing again, and continues to do so the further away you get from that ideal distance. It continually gets worse from that point on, not from starting at the muzzle. Already tried teaching you this many times. It's basic physics. It's basic ballistics. We're obviously long past the willing student phase. Now you're just willfully ignorant. It's sad.

 

[_Shorty]

Let's not forget, this is not all just theoretical. Every weekend there are benchrest shooters putting this into practice. And then there's Geoffrey Kolbe, owner of Border Barrels over in Great Britain, who shared his experimental setup and results (clickable) over on his website. And the practical results hold with the theory. He shows the muzzle trace of the 26" length and 0.943" diameter straight barrel that he was testing with, how that was measured, and made sure to point out that it was quicker than normal because it was clamped in a test rig that only left 17" of the barrel sticking out the front. The bare barrel in this test setup had shots exiting on the downslope because of how much quicker it was than normal. Being that much quicker squashed the trace over to the left enough to make that happen. The peak was pushed earlier, and the bullet exited after the peak, on the downswing. And it required a massive 200 gram weight at the muzzle in order to slow it down enough to expand the muzzle trace over to the right, pushing the peak to later in time, making the bullet exit before that peak, on the upswing.

When set up normally in a stock, rather than a test rig's barrel clamp, the barrel would be a fair bit slower because it would be vibrating along the entire 26" length, it would require a much lighter tuner to get back into the sweet spot. He notes that when in that test rig, due to the bullet exits all being on that downslope, there is horrible vertical on target. That's because faster shots leave at a higher angle than slow shots. The slower the shot is, the more time the barrel has to move downward and make the launch angle worse and worse. Since slower shots need to be launched with a higher launch angle this is obviously the worst case scenario, giving the worst possible vertical dispersion. Adding the weight to the muzzle slows it down, essentially stretching that muzzle trace further to the right, making it take longer to go through the motion. Moving it far enough so bullet exits happen during the upswing reduced that vertical dispersion, making the groups much rounder.

This is not just theory. It works in practice. Tuners aren't magic. They don't make barrels do something they aren't already doing. They simply slow down what is happening. That changes where the barrel is pointing at the time that bullets exit the muzzle. And if you can get the muzzle to be in the middle of an upswing when bullets exit then you get help with dispersion. Get the muzzle to have the upswing occur at a desired rate and you can get that dispersion minimized at a desired distance. Without the tuner the barrel is still doing what it is going to do. It just takes control over where the ideal distance out of your hands. The combination of barrel length and contour and an applicable tuner brings that variable into your control. A barrel that's more stiff increases the frequency and reduces the amplitude. A barrel that's less stiff decreases the frequency and increases the amplitude. For a given distance there is a combination that will work best. Adding a tuner to the equation allows you to fine tune things and allow for temperature.

The barrel is doing what it does with or without a tuner. A tuner just allows you to make stuff happen more slowly. That can be advantageous if other conditions are met. But it doesn't make anything magically happen that isn't happening without it. It only changes the timing and amplitude of things. If you still have bullets exiting during the upswing without the tuner, you still have a tuned distance. You may not be aware of what that distance is, but it is there. You can shoot at a bunch of different distances to find it. As I already suggested. If shots aren't all exiting during the upswing then it changes the overall behaviour quite a bit. Which is why the goal is to get it to happen for all shots during the upswing, and if possible, control the speed of the upswing so it is the speed that you want for the distance you want. Part of that is down to the contour and length chosen. You can choose a contour and length that should work well for somewhere in the 2/3 range of the cartridge's usable distance and have an all-arounder that makes the best use of that usable distance overall, or you can choose a contour and length that is just a little faster than what you require for something like 50-yard benchrest shooting and use a tuner to slow it down to just the right region. Any choice is a compromise, most particularly when you have no control over the ammo as with 22 LR.

 

[Williwaw]

I'm quite convinced that vertical dispersion can be minimized at one distance with a tuner and that without a tuner any barrel may have an optimal distance depending on it's natural/inherent state of tune or lack of tune. But am I not correct in saying that horizontal dispersion will increase with distance in all cases, even when neglecting the effect of wind.

I'm all ears anytime you want to share your ideas about tubes. Thanks Shorty.

 

[_Shorty]

I'm quite convinced that vertical dispersion can be minimized at one distance with a tuner and that without a tuner any barrel may have an optimal distance depending on it's natural/inherent state of tune or lack of tune. But am I not correct in saying that horizontal dispersion will increase with distance in all cases, even when neglecting the effect of wind.

I'm all ears anytime you want to share your ideas about tubes. Thanks Shorty.

Well, leaving wind out of the equation, when talking about the horizontal component there's nothing to affect the bullet once it leaves the muzzle. In the horizontal domain it should just continue in a straight line at whatever angle it was launched relative to POA. So it would continually increase with regard to linear distance from POA, but from an angular perspective it should just be offset by whatever angle it left at no matter what distance you check at. If it exits the muzzle with a horizontal launch angle of 0.5 MOA then it should be off by 0.5 MOA at every distance that you check. If the next shot is off by 0.25 MOA in horizontal launch angle then that would be off by 0.25 MOA at every distance. The first shot would be off by approximately 0.25" at 50 yards, or 0.5 MOA, and approx. 0.5" at 100 yards, or 0.5 MOA, and approx. 1" at 200 yards, or 0.5 MOA, while the second shot would be off by approx. 0.125" at 50, or 0.25 MOA, and 0.25" at 100, or 0.25 MOA, and approx 0.5" at 200 yards, or 0.25 MOA, etc. So the linear distance from POA should steadily increase as you checked at further and further distances from the muzzle, but the amount of angle would remain the same.

A tuner should slightly reduce the horizontal dispersion just due to the fact that it is an added mass that is slowing things down. The amplitude of movement in the horizontal domain would be reduced as a result, and so the horizontal dispersion would be reduced accordingly. It wouldn't have the same distance-specific effect that it can have in the vertical domain. You might see the amount of horizontal on target shrink and grow as you're adjusting the tuner as that affects where in the horizontal muzzle movement trace that shots will exit, but the maximum horizontal ES that you see throughout the range of adjustment should still be smaller than the horizontal ES without the tuner, since the tuner mass reduces the amplitude of the movement.

 

[Williwaw]

My next puzzler ...

What about mid-barrel tuners? They are very prevalent on the ARA circuit yet it seems to me that they would speed up swing and diminish max amplitude. Both being contrary to the conditions we seek for easy and effective tuning.

 

[_Shorty]

My next puzzler ...

What about mid-barrel tuners? They are very prevalent on the ARA circuit yet it seems to me that they would speed up swing and diminish max amplitude. Both being contrary to the conditions we seek for easy and effective tuning.

When I bought the Win52D it came with one installed, along with a Harrell tuner. I played with it a bit, just moving it from as close to the stock as I could get it, and then out towards the muzzle. I think I moved it in 1/2" increments for each test round. It definitely changes what's going on, but I never investigated much into what the idea behind it is supposed to be, and so I didn't really know what I should be doing with it other than trying that simply trial and error method. And I didn't end up leaving it on there for very long. It obviously changes how things are vibrating, as I could see effects on target, but I haven't given much thought to how it might be affecting the overall behaviour. I don't know how much of a time sink it would end up being, but some investigation into cantilevered beam engineering might yield some useful answers. You may have given me a new project, haha. Let me have a bit of a think and maybe do some investigation. Maybe best to start a new thread for mid-barrel tuners if I figure out anything worthwhile to say, heh.

 

[Longstud]

Shorty, I appreciate your answering my inquiry about posting targets in the challenge! I agree and many of the postings show large errors in target measurements. Some are maybe from lack of knowing but many are just blatant cheating. Just check the target submitted for the 1/4” challenge and it’s very apparent the first “successful” entry is falsified measurements. Great shooting bye the way.

 

[_Shorty]

Shorty, I appreciate your answering my inquiry about posting targets in the challenge! I agree and many of the postings show large errors in target measurements. Some are maybe from lack of knowing but many are just blatant cheating. Just check the target submitted for the 1/4” challenge and it’s very apparent the first “successful” entry is falsified measurements. Great shooting bye the way.

The issue we seemed to be having here and on Rimfire Central was many, many years ago. And the issue we seemed to be having was a small number of shooters seemed to be distance cheating, shooting their targets at a smaller than required distance. With some results being much too suspicious to be taken seriously. Naturally, that pissed a lot of us off. We should be able to trust each other with for-fun matches like that, but apparently some just had to do better by any means necessary. And, of course, that turned a lot of people away.

 

[_Shorty]

Mid-barrel discussion thread here at this link. FYI

 

[grauhanen]

Well, leaving wind out of the equation, when talking about the horizontal component there's nothing to affect the bullet once it leaves the muzzle. In the horizontal domain it should just continue in a straight line at whatever angle it was launched relative to POA

There is another more important influence on dispersion other than the launch angle. A center of gravity offset will also contribute to horizontal dispersion (vertical too). This has been discussed by Harold Vaughn in his book Rifle Accuracy Facts from about 1998 as well as others.

 

[_Shorty]

There is another more important influence on dispersion other than the launch angle. A center of gravity offset will also contribute to horizontal dispersion (vertical too). This has been discussed by Harold Vaughn in his book Rifle Accuracy Facts from about 1998 as well as others.

Sure, but I think we can ignore the bullet’s own contribution when we are talking about the contribution of these other things. My point was that in the vertical domain you have gravity affecting elevation on target in relation to MV, and there is nothing like horizontal gravity to affect windage on target in a similar manner. Once the bullet leaves the muzzle the vertical component on target is determined by the launch angle, the MV, and gravity. Once the bullet leaves the muzzle the horizontal component is determined by the launch angle alone, as the MV doesn’t change things, and there is no horizontal gravity. When talking about the theory side of things we tend to idealize parameters in order to understand concepts. The bullet’s CoG will indeed play a part in final dispersion, but the bullet we’d be using for the sake of discussion would be ideal, and so the dispersion component from wobbling would be zero since there would be zero wobble. Just as we are eliminating wind for the sake of discussion, when wind would always play an actual part in the matter.

 

[grauhanen]

Sure, but I think we can ignore the bullet’s own contribution when we are talking about the contribution of these other things. My point was that in the vertical domain you have gravity affecting elevation on target in relation to MV, and there is nothing like horizontal gravity to affect windage on target in a similar manner. Once the bullet leaves the muzzle the vertical component on target is determined by the launch angle, the MV, and gravity. Once the bullet leaves the muzzle the horizontal component is determined by the launch angle alone, as the MV doesn’t change things, and there is no horizontal gravity. When talking about the theory side of things we tend to idealize parameters in order to understand concepts. The bullet’s CoG will indeed play a part in final dispersion, but the bullet we’d be using for the sake of discussion would be ideal, and so the dispersion component from wobbling would be zero since there would be zero wobble. Just as we are eliminating wind for the sake of discussion, when wind would always play an actual part in the matter.

That is a convenient way of saying that by continuing to ignore something important the problematic explanation remains correct.

It's curious that, with or without a tuner, group shape tends to be round, with similar amounts of vertical and horizontal spread. In the vertical dimension there are two forces at play -- the changing launch angle and MV variation. Yet in the horizontal dimension, MV variation plays no role.

 

[grauhanen]

While we're at it, consider this from Shorty's post #27 above.

Dispersion is best at one distance for a given barrel and a given ammo. Starting from the muzzle, dispersion increases until about halfway between the muzzle and that ideal distance. From about the halfway point until the ideal distance it begins decreasing again. Dispersion is at a minimum at that ideal distance. And once it passes that ideal distance it begins growing again, and continues to do so the further away you get from that ideal distance. It continually gets worse from that point on, not from starting at the muzzle. ...It's basic physics. It's basic ballistics.

Pick an "ideal distance". Could be 50, 80, or 100 yards (or something else). The ideal distance is the one at which a barrel and lot of ammo achieve a "natural tune" (or positive compensation).

According to Shorty, dispersion (group size in terms of MOA) increases until about halfway between the shooter and the ideal distance. Then group size begins to shrink until the ideal distance is reached.

In other words, convergence is achieved, where group size (in MOA) is better further out than it is halfway there.

Who knew that results with .22LR can be better further out than closer in?

 

[_Shorty]

That is a convenient way of saying that by continuing to ignore something important the problematic explanation remains correct.

It's curious that, with or without a tuner, group shape tends to be round, with similar amounts of vertical and horizontal spread. In the vertical dimension there are two forces at play -- the changing launch angle and MV variation. Yet in the horizontal dimension, MV variation plays no role.

Me: "Hey, Chat-GPT, is it commonplace to idealize some parameters in a system when discussing and/or trying to learn about theory, when in reality some parameters actually contain some random variance? For example, physical objects not being 100% idential from example to example, having variance in dimensions due to manufacturing tolerance and/or physical damage due to fragility, and things of that nature. While those things have to be taken into account when a theory is put into practice, is it not generally acceptable to discuss as though everything were perfect in order to illustrate or teach the theories involved in any given field?"

Chatp-GPT: "Yes, that is very commonplace.

In theory and teaching, it is standard practice to idealize parameters, assume perfect conditions, and strip away messy real-world complications so that the fundamental relationships are clear. For example:

• Physics often treats objects as perfectly rigid, frictionless, or identical in size and shape.
• Engineering will model beams or circuits as though materials are uniform, tolerances nonexistent, and wear doesn’t occur.
• Economics assumes "rational actors" or "perfect information" when introducing models, even though reality is more chaotic.

These simplifications make it possible to express the governing principles without the noise of random variation. Once the base theory is understood, practical refinements are introduced—things like manufacturing tolerances, fragility, material fatigue, environmental noise, or other sources of variance.

So yes: it’s not just acceptable, it’s the norm. The process usually goes in two stages:

1. Build understanding with the perfect case.
2. Incorporate real-world imperfections later, either as correction factors, probabilistic models, or design tolerances.

This balance between idealized models and practical considerations is how most fields are taught and developed."

While we're at it, consider this from Shorty's post #27 above.

Pick an "ideal distance". Could be 50, 80, or 100 yards (or something else). The ideal distance is the one at which a barrel and lot of ammo achieve a "natural tune" (or positive compensation).

According to Shorty, dispersion (group size in terms of MOA) increases until about halfway between the shooter and the ideal distance. Then group size begins to shrink until the ideal distance is reached.

In other words, convergence is achieved, where group size (in MOA) is better further out than it is halfway there.

Who knew that results with .22LR can be better further out than closer in?

It's called basic ballistic theory. That's literally how it works for all projectiles fired from flexible barrels, from 17 HM2 all the way up to 800 mm Schwerer Gustav railway guns. Barrel harmonics cause slight variations in launch angles. Couple that with slight variations in muzzle velocity and you get stuff like this:



Largest divergence between muzzle and target is about halfway there when you're tuned for that target's distance. Interesting how that works, eh? It's almost like the bullets' flight paths follow some kind of rules... I wonder if any of those rules might explain why it is only "about halfway there" and not "exactly halfway there"...