calling all LONG RANGE SHOOTING experts!
- Thread starter beerengineer
- Start date
47.07 Hz means that the barrel will have 47.07 oscillations per second. Longitudinally, this means (I believe) that a vibration will travel the length of the barrel and back 47.07 times per second. Vertically, this means that the tip of the barrel will move up and down 47.07 times per second. Given the total flight time of the bullet, and knowing the frequency of the barrel, you can find the point in space and the relative trajectory of the bullet as it leaves the barrel.
For instance, if a bullet takes .0106 seconds to leave the barrel (assuming time=0 as the instant that the 47.07 Hz vibration begins) .0106 seconds * 47.07 oscillations/second gives ~.499 of an oscillation before the bullet leaves the barrel. Since one oscillation is one period of the sinusoid, this means that the bullet will leave the barrel at almost the exact middle of a period.
For sinusoid periods, the beginning, middle, and end are all at 0 (assuming that the beginning is 0). Since the bullet leaves the barrel in the middle of a period, it will be leaving the barrel at a displacement of 0 and thus will leave the barrel with the closest possible "flat" initial trajectory.
Knowing the frequency of a barrel and the time it takes for a bullet to leave the barrel (when you know that time in relation to frequency
) you can tell the exact angle a bullet will leave the barrel.
Does all of that make sense?
For instance, if a bullet takes .0106 seconds to leave the barrel (assuming time=0 as the instant that the 47.07 Hz vibration begins) .0106 seconds * 47.07 oscillations/second gives ~.499 of an oscillation before the bullet leaves the barrel. Since one oscillation is one period of the sinusoid, this means that the bullet will leave the barrel at almost the exact middle of a period.
For sinusoid periods, the beginning, middle, and end are all at 0 (assuming that the beginning is 0). Since the bullet leaves the barrel in the middle of a period, it will be leaving the barrel at a displacement of 0 and thus will leave the barrel with the closest possible "flat" initial trajectory.
Knowing the frequency of a barrel and the time it takes for a bullet to leave the barrel (when you know that time in relation to frequency
) you can tell the exact angle a bullet will leave the barrel.Does all of that make sense?
In the words of Squint Eastwood
"If you're gonna talk,talk,if you're gonna shoot,shoot."
You have a rifle,you have a scope,you have ammo.
The fantasy parameter is a mental issue.
What if your first group is 9 inches bigger than you hoped at 1760yds.Did you have fun?Try a Berger,or another powder,vary seating depth.
When you find your equiptment/ammo sweet spot,time to work on yourself!!
When you are good enough to outshoot that Sendero,
build some Nesika Bay fancy ultimate super rifle
Suitable cartridge,load,and bullet for your adventure,I think a guy with a 3/4 or even 1 moa rifle at 300 yds,can wear his barrel out developing his own skills before he will be outshooting his rifle at those ranges.
I am the prototype machinist that spent 30 years in new product development that took the dreams od dozens of engineers,and read your drawings,sometimes crayon on napkin,and sawed,milled,ground,filed,scraped,burned,baked and concurrent engineering reworked your mind changes,and sometimes showed you a better way(engineers)
In the end,my hands gave you what you needed.
All this whizzing does not amount todiddly squat.
Old goobers like kraigwy
were shooting 1000 yd groups of 12 or 15 in at 1000 yds with blackpowder,pig lead and iron sights in the late 1800's
Some of those old goobers forge welded a strip of steel around a mandrel,made their own square reamers to scrape the hole true,lapped it,then wound wood strips around a fencepost for a helix and pulled it through a wood box ,pulling a wood rod with a hand filed cutter to make the rifling. They shot groups at 220 yds with those rifles and iron sights in the 1 moa range
See Ned Roberts books.
I will give way more credit to a man like Kreiger who can drill a hole,cut some grooves,,and hand lap it so it will shoot than a bunch of academics with calculators trying to have a whizzing contest about how brilliant they are.
Any moron with a pencil can write +/- .0002 on a piece of paper.Few have any clue how to measure it,and fewer still can cut it..
Then some can do it drilling a 30inch long hole,straight and true.They were doing it before they even made calculators or computers.
Just go shoot!!
"If you're gonna talk,talk,if you're gonna shoot,shoot."
You have a rifle,you have a scope,you have ammo.
The fantasy parameter is a mental issue.
What if your first group is 9 inches bigger than you hoped at 1760yds.Did you have fun?Try a Berger,or another powder,vary seating depth.
When you find your equiptment/ammo sweet spot,time to work on yourself!!
When you are good enough to outshoot that Sendero,
build some Nesika Bay fancy ultimate super rifle
Suitable cartridge,load,and bullet for your adventure,I think a guy with a 3/4 or even 1 moa rifle at 300 yds,can wear his barrel out developing his own skills before he will be outshooting his rifle at those ranges.
I am the prototype machinist that spent 30 years in new product development that took the dreams od dozens of engineers,and read your drawings,sometimes crayon on napkin,and sawed,milled,ground,filed,scraped,burned,baked and concurrent engineering reworked your mind changes,and sometimes showed you a better way(engineers)
In the end,my hands gave you what you needed.
All this whizzing does not amount todiddly squat.
Old goobers like kraigwy
were shooting 1000 yd groups of 12 or 15 in at 1000 yds with blackpowder,pig lead and iron sights in the late 1800'sSome of those old goobers forge welded a strip of steel around a mandrel,made their own square reamers to scrape the hole true,lapped it,then wound wood strips around a fencepost for a helix and pulled it through a wood box ,pulling a wood rod with a hand filed cutter to make the rifling. They shot groups at 220 yds with those rifles and iron sights in the 1 moa range
See Ned Roberts books.
I will give way more credit to a man like Kreiger who can drill a hole,cut some grooves,,and hand lap it so it will shoot than a bunch of academics with calculators trying to have a whizzing contest about how brilliant they are.
Any moron with a pencil can write +/- .0002 on a piece of paper.Few have any clue how to measure it,and fewer still can cut it..
Then some can do it drilling a 30inch long hole,straight and true.They were doing it before they even made calculators or computers.
Just go shoot!!
It doesn't really matter what the "exact angle a bullet leaves the barrel", what matters is that it leaves the same spot every time.
In building a rifle, you don't care about the exit angle, you care that that exit angle is not disturbed.
It's called "consistency", that's why we take care in bedding and free floating.
Barrels get hot and expand which doesn't really hurt anything until you disturb the vibrations.
There is such a thing and "over mathing" the shooting game. We reach a point of diminishing returns when we should be working on marksmanship fundamentals.
sorry if I gave you the wrong impressionKraig sez:
And one of the USA service rifle teams testing M14NM's in accuracy cradles through 600 yards learned those semiautos had a small amount of compensation at 600 yards. Probably caused by the gas port's position being about mid point in the barrel caused it to bow up at that point right after the bullet passed it. By the time the bullet got to the muzzle, the bore axis at the muzzle would be pointing down a bit more. Faster bullets had higher port pressure so pointing them down a bit compensated for their flatter trajectory.
Check out the "with" and "without" tuner sections of:
http://www.varmintal.com/apres.htm#WithoutTuner
I don't agree. Neither to the British Commonwealth fullbore shooters who proved their SMLE .303's shooting arsenal ammo full of cordite had such a high muzzle velocity spread that was compensated for by the barreled action's vertical whipping. Tests showed the bullets left on the up swing of the barrel; faster ones left sooner, slower ones left later. This compensated for the large spread in muzzle velocity and they shot more accurate at 800 to 1000 yards than from 300 to 600. Which is why the Brits preferred Mauser 98 style actions for 300 - 600 yards. Their front locking bolt design didn't flex as much as the SMLE's rear locking style and shot more accurate at the shorter ranges.
And one of the USA service rifle teams testing M14NM's in accuracy cradles through 600 yards learned those semiautos had a small amount of compensation at 600 yards. Probably caused by the gas port's position being about mid point in the barrel caused it to bow up at that point right after the bullet passed it. By the time the bullet got to the muzzle, the bore axis at the muzzle would be pointing down a bit more. Faster bullets had higher port pressure so pointing them down a bit compensated for their flatter trajectory.
Check out the "with" and "without" tuner sections of:
http://www.varmintal.com/apres.htm#WithoutTuner
Heat of the metal is never used in calculating moment of inertia; the number that represents how stiff or rigid a barrel is. So their vibrations won't change as they heat up. Their fundamental whipping frequency stays the same as they go from cold to hot. Too many folks have shot 30 or more shots at long range testing rifles and no shift in bullet impact occured; accuracy was 1/2 MOA or better all the time. In one test, 40 shots fired 20 to 30 seconds apart at 600 went under 2 inches.
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bpeezer mentions:
Your next comment was correct; the barrel vibrates or whips at right angles to its axis at 47+ times a second. It's virtually all in the vertical axis 'cause the recoil axis (the bore) is aligned above the stock's butt plate that's against your shoulder.
Sound and shock waves travel in stainless steel about 5600 fps. The shock of the round firing takes about .00018 second to travel one foot. It takes about .00036 second to go from chamber to muzzle in a 24 inch barrel. .308 Win. bullets take about .0012 second to go from case to muzzle. So that shock wave from the round firing makes several breech to muzzle round trips while a .308's bullet is going down the barrel.
I noticed this comment yesterday then forgot to comment about it.
Your next comment was correct; the barrel vibrates or whips at right angles to its axis at 47+ times a second. It's virtually all in the vertical axis 'cause the recoil axis (the bore) is aligned above the stock's butt plate that's against your shoulder.
Sound and shock waves travel in stainless steel about 5600 fps. The shock of the round firing takes about .00018 second to travel one foot. It takes about .00036 second to go from chamber to muzzle in a 24 inch barrel. .308 Win. bullets take about .0012 second to go from case to muzzle. So that shock wave from the round firing makes several breech to muzzle round trips while a .308's bullet is going down the barrel.
Would your calculations all work out the same if the receiver flexes?What about the alloy/hardness level of the steel?Will a cut rifled,button rifled,or hammer forged barrel respond the same?
If a barrel gets fluted,is it before or after stress relief?
Are you assuming total free float from the receiver ring forward/
What about subtle differences in contour barrel to barrel,as the turn marks are polished out?
What about the differences between a Shilen and a Douglas or a Lilja contour?
I agree barrels are dynamic when fired .You can calculate a general idea.IMO,actual results involve the interactions of several variables.You can solve for "X".Real world,"X" will be modified by "Y","Z",etc,and the value of of those might vary.
You can buy 10 barrels of the same length and contour,they may have relatively similar harmonics,but by the time they become 10 rifles ,some in Remingtons,some in Mausers,and some in benchrest tube receivers,it is still going to come down to "tuning the trim" which is often done with ammunition
If a barrel gets fluted,is it before or after stress relief?
Are you assuming total free float from the receiver ring forward/
What about subtle differences in contour barrel to barrel,as the turn marks are polished out?
What about the differences between a Shilen and a Douglas or a Lilja contour?
I agree barrels are dynamic when fired .You can calculate a general idea.IMO,actual results involve the interactions of several variables.You can solve for "X".Real world,"X" will be modified by "Y","Z",etc,and the value of of those might vary.
You can buy 10 barrels of the same length and contour,they may have relatively similar harmonics,but by the time they become 10 rifles ,some in Remingtons,some in Mausers,and some in benchrest tube receivers,it is still going to come down to "tuning the trim" which is often done with ammunition
Coyote_Buster700
New member
Well heck yeah, I do that with my Mini-14 daily.
My head hurts...
I'm with the group that sez do your load development (OCW or however you see fit) and send at least a couple of hundred rounds down tube every month, in less than ideal conditions.
The wind will have faaarrr more effect on the POI than anything else we're discussing.
I'd rather get better at "hittin what I'm aiming at" in the field than at the calculator.
I'm with the group that sez do your load development (OCW or however you see fit) and send at least a couple of hundred rounds down tube every month, in less than ideal conditions.
The wind will have faaarrr more effect on the POI than anything else we're discussing.
I'd rather get better at "hittin what I'm aiming at" in the field than at the calculator.
I read thru this thread and yes I am familiar with LR shooting and over the years have covered much of the same ground that has been covered here and it causes me to think about what an old guy at a range I use to be a member at would say when one got down to minutia of shooting...
Son, the rifle and the bullet don't know that it is impossible for a stock service rifle to shoot a less than MOA (10.47 in) 10 shot group at 1000 yards and so they aren't concerned about it in the least...read the wind...be consistent and shoot..don't over think it..and at the end of the day you might just get that pretty ribbon...
Best advice I ever received.
Son, the rifle and the bullet don't know that it is impossible for a stock service rifle to shoot a less than MOA (10.47 in) 10 shot group at 1000 yards and so they aren't concerned about it in the least...read the wind...be consistent and shoot..don't over think it..and at the end of the day you might just get that pretty ribbon...
Best advice I ever received.
HiBC asks:
I also thing fluting a barrel is a waste of time and money. There's no accuracy difference between them. Fluting a barrel makes it less stiff or rigid than it was. The cooling effect is small but good barrels properly fit to receivers don't walk shot impact as they heat up.
No, not exactly. But very close. There seems to be a noticable difference between front locking ones (Mauser 98 style) and the rear locking ones (British SMLE). The software Tom Irvine developed for me only calculates the rigidity for drilled blanks; no rifling or chambers. So there will be a small difference. With the breech end fixed in a receiver that's bolted into a stock, the numbers derived are close enough to make comparisons.
Each type of steel will have different qualities. Google a search for "moment of inertia steel" and some of the results will have tables showing different steel's structure. There's not much difference between steels used in most rifle barrels.
They'll be virtually the same. As long as the outside and bore dimensions, as well as the metal type, are the same. That software doesn't calculate the land and groove dimensions but they don't have much effect. I did some calculations based on a 1.1" diameter 24" barrel blank with a .3055" diameter hole (has the same area to the .300 Win. Mag. SAAMI specs for a 30 caliber rifled bore), then changed the it to .001" larger. Then ran another set with only the outside diameter being .001" larger The difference in the blank's resonant frequency changed less than 1/10 percent; an insignificant amount.
I think barrels are best fluted before a gun drilled blank is reamed to bore diameter then rifled and lapped. Otherwise, fluting caused internal dimensional changes. Ready to shoot hammer forged barrels get tighter groove diameters after fluting, button rifled ones get larger. Cut rifle barrels change the least, but it's a gamble.
I also thing fluting a barrel is a waste of time and money. There's no accuracy difference between them. Fluting a barrel makes it less stiff or rigid than it was. The cooling effect is small but good barrels properly fit to receivers don't walk shot impact as they heat up.
Yes. Anything touching the barrel forward of the receiver will end up putting pressure on the barrel and that'll cause accuracy problems. Only if the pressure's always at same place with the same force and same direction will it be repeatable.
Any difference between barrel contour dimensions will make one stiffer (or flimsier) than the other. But polishing out tool marks have virtually no effect. See above about the .001" difference in outside diameter changes.
They'll all be the same for the same barrel metal contoured to the same profile and having the same inside and outside dimensions. Barrel steels are not sensitive to who shapes them. A given steel has the same properties regardless of who reshapes it.
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bpeezer, your graph shows how the relative displacement of the tip of the barrel changes with respect to time. I think the best place for a bullet to leave is just before it reaches the top at the +1 line. That's the place where there's the least amount of vertical change in angle for a given amount of time. And bullets leaving later at a higher point do so 'cause they're slower and have a lower muzzle velocity. So they are helped down range by leaving at a greater angle. The opposite's the case for faster bullets; they'll leave at a lower angle. Vertical shot stringing is reduced.
Bullets leaving at the zero point do so when the greatest angular change takes place for a given amount of time. All bullets leaving when the muzzle axis is moving down will have opposite results than when the axis is moving up. Faster ones will leave at a higher angle, slower ones at a lowere angle. And that'll increase vertical shot stringing.
Bullets leaving at the zero point do so when the greatest angular change takes place for a given amount of time. All bullets leaving when the muzzle axis is moving down will have opposite results than when the axis is moving up. Faster ones will leave at a higher angle, slower ones at a lowere angle. And that'll increase vertical shot stringing.
HiBC,
Here something that Lilja did on barrels it relate to BR barrels and LR barrels
http://www.riflebarrels.com/articles/barrel_making/rigidity_benchrest_rifles.htm
Here something that Lilja did on barrels it relate to BR barrels and LR barrels
http://www.riflebarrels.com/articles/barrel_making/rigidity_benchrest_rifles.htm
Bart, I was hoping for the bullets to leave the barrel nearest the zero point as the barrel is on an upward swing, not a downward one. That way the slower shots would leave with the barrel pointing slightly upwards, just like you suggested. My reasoning for that was twofold: First, that the shots could be ballistically treated as fired directly horizontal so that scope adjustments will be accurate. My second reason, and I'm sure you can shed some light on this "theory", was relative inertia imparted from the motion of the barrel would be most similar around this point. The derivative of my original curve (also a sinusoid) would have a max or min at this point, meaning that the rate of the barrel whipping will NOT be changing at this point, so hopefully the change in inertia will be minimal and can be ignored in calculations.
Also, thanks for straightening me out on the longitudinal frequency. That helped a lot
Also, thanks for straightening me out on the longitudinal frequency. That helped a lot
bpeezer comments:
Second, the barrel's motion will be very fast at the mid point. For a given small spread in barrel time, if they bullets leave around that point, they'll have the greatest angular difference for their departure angle.
I'll add something else. Your bullets will be long gone before the barrel gets pointed back down straight out at the zero point after it goes up through zero while the bullet's still in the barrel. When fired, the muzzle axis has beed pointing down a bit due to barrel weight, then it starts moving up, quickly goes past zero (if zero can be the long axis of the receiver), then on up towards it's high point. Most bullets leave just before the high point when best accuracy happens. Then the muzzle axis goes over the top and starts back down to zero. It whips a few complete cycles while the bullet's on the way to the target.
First, your scope adjustments will be accurate regardless of where in the muzzle whip cycle the bullet's fired at. They all leave about the same place in the muzzle's whip cycle. You adjust your scope to move bullet impact to some other place, not where they start out from.
Second, the barrel's motion will be very fast at the mid point. For a given small spread in barrel time, if they bullets leave around that point, they'll have the greatest angular difference for their departure angle.
I'll add something else. Your bullets will be long gone before the barrel gets pointed back down straight out at the zero point after it goes up through zero while the bullet's still in the barrel. When fired, the muzzle axis has beed pointing down a bit due to barrel weight, then it starts moving up, quickly goes past zero (if zero can be the long axis of the receiver), then on up towards it's high point. Most bullets leave just before the high point when best accuracy happens. Then the muzzle axis goes over the top and starts back down to zero. It whips a few complete cycles while the bullet's on the way to the target.
I wasn't aware of the average time it takes bullets to get down barrels so I was assuming more oscillations. Also, the more I think about it the more I agree with you about the bullet leaving at the top of the curve. The barrel will be traveling the slowest and give the greatest consistency between shots that slightly vary. I got myself all confused thinking too much about the derivative thanks for digging me out again haha
thanks for digging me out again haha