This isn't a competition. I believe sharing theories and information is the core of this thread. I have learned something from sweetshooter, and bart, and didn't even bother to thank them. I hope maybe they learned something from me. It's taken a long time for shooters, and barrel makers as to what makes a gun accurate, and there are still unanswered questions. I want to soak up as much info as I can.
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walking group
- Thread starter BB1
- Start date
This isn't a competition. I believe sharing theories and information is the core of this thread. I have learned something from sweetshooter, and bart, and didn't even bother to thank them. I hope maybe they learned something from me. It's taken a long time for shooters, and barrel makers as to what makes a gun accurate, and there are still unanswered questions. I want to soak up as much info as I can.
603Country
New member
This thread isn't a competition but Bart and Sweet (both very knowledgable guys) are sure competing or trying to one-up with theories of barrel vibration. Sure the barrels vibrate. We all know that. The OP knows that, but the info put forth on vibration is not going to help him at all. That's why I suggested that if we want to actually help the guy, who did request our assistance, we need to suggest something a bit more practical than detailed theories of barrel whip. Of course, that practical info is already in the various posts, and the OP may have already taken action to fix his problem. I hope that he'll eventually tell us what did fix the problem. I'd like to know.
And I most certainly agree that I've learned a ton of things on this forum. It's made me a better reloader and a better shot, and I don't think I've ever thanked anyone for the bits of info that have been extremely helpful.
And I most certainly agree that I've learned a ton of things on this forum. It's made me a better reloader and a better shot, and I don't think I've ever thanked anyone for the bits of info that have been extremely helpful.
Sweet Shooter, if you mean you're laying a finger on that guitar string then plucking it, yes that will change its resonant frequency. Without that finger on it, I think it makes the same note every time it's plucked.
Your reference to A on a keyboard at 440 Hz got me to thinking about a standard sporter weight 30 caliber 3.4 pound 24 inch barrel's resonant frequency. With both ends free its resonate frequency is at about 264 Hz.
Screw the breech end into a receiver bolted in a stock and its resonant frequency goes down to about 68 Hz. This is the one that causes the greatest angular swing of the muzzle axis.
If you smack that barrel with a hammer, it'll ring at a frequency much higher than these; couple thousand Hz for example.
Your reference to A on a keyboard at 440 Hz got me to thinking about a standard sporter weight 30 caliber 3.4 pound 24 inch barrel's resonant frequency. With both ends free its resonate frequency is at about 264 Hz.
Screw the breech end into a receiver bolted in a stock and its resonant frequency goes down to about 68 Hz. This is the one that causes the greatest angular swing of the muzzle axis.
If you smack that barrel with a hammer, it'll ring at a frequency much higher than these; couple thousand Hz for example.
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Bart B, that assumes that the tension on the string remains constant, a combined function of both the key, and the temperature - temperature will affect both the length of the string, and the shape of the neck.
Which actually is a good parallel for the rifle.
603Country, sometimes a discussion of theory helps people understand why the different, practical methods work, or which of the practical methods is more likely to apply.
Whether the OP needs to do anything is another matter. He has a hunting gun, not a target gun, and apparently his groups are fine until he has fired several magnum rounds. He just needs to allow cooling off time between his groups, when sighting in the rifle, and may not need the expense or effort required to free float it or fully bed it.
If he were planning on being able to use it for extended shooting scenarios, that would be different.
Which actually is a good parallel for the rifle.
603Country, sometimes a discussion of theory helps people understand why the different, practical methods work, or which of the practical methods is more likely to apply.
Whether the OP needs to do anything is another matter. He has a hunting gun, not a target gun, and apparently his groups are fine until he has fired several magnum rounds. He just needs to allow cooling off time between his groups, when sighting in the rifle, and may not need the expense or effort required to free float it or fully bed it.
If he were planning on being able to use it for extended shooting scenarios, that would be different.
Sweet Shooter
New member
@Bart B. Sweet Shooter, if you mean you're laying a finger on that guitar string then plucking it, yes that will change its resonant frequency. Without that finger on it, I think it makes the same note every time it's plucked.
Bart, this is not the case. Almost and maybe in a perfect world and to all extents and purposes yes absolutely, but not quite in this case.
@coyota1... Thank you.
@BB1... If you're still around... pressure pad+paracord
@603Country... Take a nap. I didn't mean to offend anyone. Sorry.
-SS-
For those who think a rifle barrel's resonant frequency significantly changes enough to be noticed with different forces applied to it as well as its temperature in a range where humans survive, please contact Tom Irvine at:
tom@vibrationdata.com
...about his website:
http://www.vibrationdata.com/StructuralFE.htm
...then tell him to fix his software in the above web site that's named below:
"Natural frequency of a rifle barrel with free-free boundary conditions."
so it will match your theories of how such things will happen.
Then be ready to explain why his software is wrong.
Also, contact the American Society of Mechanical Engineers and have them suscribe to your theories because if Tom Irvine's wrong, there's got to be hundreds (thousands?) of engineers working with vibration issues that are also wrong.
tom@vibrationdata.com
...about his website:
http://www.vibrationdata.com/StructuralFE.htm
...then tell him to fix his software in the above web site that's named below:
"Natural frequency of a rifle barrel with free-free boundary conditions."
so it will match your theories of how such things will happen.
Then be ready to explain why his software is wrong.
Also, contact the American Society of Mechanical Engineers and have them suscribe to your theories because if Tom Irvine's wrong, there's got to be hundreds (thousands?) of engineers working with vibration issues that are also wrong.
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603Country
New member
Sweetshooter, I took my nap, had breakfast, and the competition/disagreement/argument is still on. That's Ok.
Bart B, the rifle responds to temperatures in a range created by firing of its cartridges. Humans don't survive in rifle barrel temperature ranges, especially not temperatures such as those created by seven or more shots (OP said problems start sfter first two groups) of .300 Wby Mag.
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MLeake, I know that. I explained why in post 5 for this thread:
Yes, I've heard of and seen the BOSS system on Browning rifles. Adjusting it changes the length of the barrel mass which changes the barrel's resonant frequency a small amount. It does not tune barrel vibration so a given load leaves the muzzle at a neutral point in the barrel's sine wave oscillation. There's no way anyone could verify that without accelerometers on the barrel feeding computer software along with bullet exit times to verify it did. If by "neutral point" you mean when the muzzle axis is straight out from the chamber, that's the worst place to have bullets exit. That's where the muzzle axis goes through the greatest amount of angular vertical swing in a given amount of time. There's no way one could get muzzle velocity spread low enough to do that consistantly. Also, if the muzzle axis is on the down swing as it goes through that point, faster bullets will leave at a higher angle and slower ones at a lower one; exactly the opposite of what's best. So one would have to ensure the muzzle axis is on the up swing when that happens. And muzzle velocity spread would need to be much smaller than what's acceptable for the best place in the vertical plane to leave at.
Browning claims their BOSS adjusts the barrel whip so bullets leave at the top or bottom point in the muzzle axis' vertical swing. I don't know if they proved that with equipment to acutally measure bore axis angle vs. bullet exit or just assumed this to be so like virtually everyone else making such claims.
It's best to have the bullet exit just before the muzzle axis reaches its highest point so some compensation for velocities faster and slower than the average would leave such that their trajectories would be corrected for. A very small spread in velocity is not needed. And this is what the BOSS system does if it's set correctly. This was proved over a hundred years ago with the British .303 ammo in their service rifles.
One can do the same thing much cheaper with the same results than a BOSS system does by just changing their powder charge weight a bit to change the bullet's barrel time from case mouth to out the muzzle.
With the right set of components in a given load, all the bullets fired from several barrels with different resonant frequencies will shoot sub 1/2 MOA at 600 yards with ease. That was proved years ago in long range competitive shooting. But for short range with .22 rimfire ammo, such "tuners" are popular and they do work well if one cannot find a lot of ammo that has the right barrel time for their barrel's vibrating characteristics.
His barrel's fundamental/resonant frequency doesn't have anything to do with that.Barrels walking point of impact as they heat up is typically caused by the barrel is fit to the receiver with uneven pressure around where its flat part is against the receiver. If the receiver face is not square with the chamber axis, there'll be one point where the barrel is hardest against the receiver. As the barrel heats up and expands, a stress line at that point makes the barrel whip more and more in one direction as it gets hotter. Which is why, after letting the barrel cool down, it shoots back to point of aim where it started. This cause is easy to fix; face off the receiver and shim the barrel so it clocks into the same place keeping headspace correct.
If a barrel's not properly stress relieved, they also will bend a bit as they heat up. Replacing it is the only solution.
Yes, I've heard of and seen the BOSS system on Browning rifles. Adjusting it changes the length of the barrel mass which changes the barrel's resonant frequency a small amount. It does not tune barrel vibration so a given load leaves the muzzle at a neutral point in the barrel's sine wave oscillation. There's no way anyone could verify that without accelerometers on the barrel feeding computer software along with bullet exit times to verify it did. If by "neutral point" you mean when the muzzle axis is straight out from the chamber, that's the worst place to have bullets exit. That's where the muzzle axis goes through the greatest amount of angular vertical swing in a given amount of time. There's no way one could get muzzle velocity spread low enough to do that consistantly. Also, if the muzzle axis is on the down swing as it goes through that point, faster bullets will leave at a higher angle and slower ones at a lower one; exactly the opposite of what's best. So one would have to ensure the muzzle axis is on the up swing when that happens. And muzzle velocity spread would need to be much smaller than what's acceptable for the best place in the vertical plane to leave at.
Browning claims their BOSS adjusts the barrel whip so bullets leave at the top or bottom point in the muzzle axis' vertical swing. I don't know if they proved that with equipment to acutally measure bore axis angle vs. bullet exit or just assumed this to be so like virtually everyone else making such claims.
It's best to have the bullet exit just before the muzzle axis reaches its highest point so some compensation for velocities faster and slower than the average would leave such that their trajectories would be corrected for. A very small spread in velocity is not needed. And this is what the BOSS system does if it's set correctly. This was proved over a hundred years ago with the British .303 ammo in their service rifles.
One can do the same thing much cheaper with the same results than a BOSS system does by just changing their powder charge weight a bit to change the bullet's barrel time from case mouth to out the muzzle.
With the right set of components in a given load, all the bullets fired from several barrels with different resonant frequencies will shoot sub 1/2 MOA at 600 yards with ease. That was proved years ago in long range competitive shooting. But for short range with .22 rimfire ammo, such "tuners" are popular and they do work well if one cannot find a lot of ammo that has the right barrel time for their barrel's vibrating characteristics.
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