How long does a barrel vibrate after firing, Calfee?

My piece of anecdotal data

I had a rail gun that shot phenomenal.....legendary if you will. I could pull the trigger as soon as it hit the stop or wait until the wind was right. Either way it shot the same and to the same place - mix and match.

That barrel wore out and the next one shot pretty good but my groups doubled in size if I didn't wait a second or two after it hit the stop. I deliberately shot it both ways and it was competitive if I paused and non-competitive if I fired it quickly - every time!

Using a "rail" system, you can look through your scope and see the effect of pushing the rifle against the stop. You can't see much of the same when the rifle is fired and if any it doesn't last nearly as long.
 
Bill Wynne said:
How long does a barrel vibrate after firing? That is the question.

Forever! It will get less and less over time, but if you let it, it will just lay there and quiver. With each added shot it will quiver differently.
Concho Bill
Click to expand...

I forgot to add, while you are waiting for the quivering to stop, if the wind conditions return, go ahead and shoot. The wind conditions are much more of a factor.

Concho Bill
 
Maybe with this rapid firing, we are not allowing the vibrations in the SHOOTER to stabilize before the next shot. Just a thought:eek:.
Regards,
Don.H.
 
railfly

Doug,
Be sure and see how much it vibrates when you yell at it.
 
Why?, Why?, Why do some of you folks have so much time on your hands to think up these inconsequential things?
 
Because it is our time

plumbago said:
Why?, Why?, Why do some of you folks have so much time on your hands to think up these inconsequential things?
Click to expand...

If any of this made any sense it would be too much like work and we would not do it.:)

Concho Bill
 
Bill does come up with some interesting questions, As no one here can honestly answer or at least I don't think they can, maybe we can also ask for ideas on the best way to measure and quantitfy this great question. I was watching you tube video's through the view of rifle scopes people had recorded the other evening and although it was not necessarily the bbl the red dot sight's, dot vibrated for about 2 seconds or so. my guess is that it might just be long enough to be a concern on a quick turn around shot. If nothing else it needs to be examined.
 
Sometime ago Will posted lots of vibrations graphs and info here.
Hope you save those because it answers the questions.
Fred K

Tuner Tuning For Dummies!
By WillH

This is an analysis of an experiment with a single focus. The purpose was to observe wave patterns of a rifle barrel, with a tuner attached, then examine their behavior during actual firing. The author believed current technology existed to conduct the entire study with uncomplicated instrumentation and equipment.

While the entire investigation took several weeks to complete only the final data collection period will be presented. Most of the preliminary testing was to verify instrumentation, test procedures and identify uncontrollable variables.

Equipment:

Cooper LVT .22 LR cal.
Fuddham Tuner 14.0 oz.
Ammunition: SK Standard Plus lot #17138/23064
Fluke 123 Meter scope
MS (Measurement Specialties): ACH-01-03/10 Accelerometer, SDT-1-028K Piezo Film, ACH-01 Amplifier.

Test Procedure:

The tuner was modified to accept attachment of MS ACH-01 Accelerometers. Flats were machined at 90 degree angles (Vertical and Horizontal). The accelerometers were attached to the tuner with the ceramic bottom of the MS ACH-01 in physical contact with the tuner and were held in place with a fillet weld of Hot Glue along both sides. The MS ACH-01’s were mounted with the connection leads parallel to the bore of the barrel. One MS ACH-01 was mounted level and perpendicular to the vertical axis using a bubble level. (Note: The Horizontal sensor was not used during this test.)

The tuner was attached to the barrel with OEM clamping screws.

The SDT-1 Piezo Film was placed at the muzzle with a support bracket. The film was positioned so it covered approximately 2/3 of the muzzle opening (Tuner opening) approximately ½ inch from the muzzle. (Note: The intent was to have the bullet strike the piezo film. When test dispersion groups were fired the SDT-1 was moved away from the muzzle. )

The rifle was positioned on a Hart rest and top with the butt stock supported by a rear bag. Standard benchrest shooting configuration.

The ACH-01 Amplifier was attached to ACH-01-03 and also connected to the A channel of the Oscilloscope. The SDT-1-028K Piezo Film was connected to the B channel without amplification.

All tests shooting was done at an out door 50 yd. range. Temperature 92 degrees, humidity 25%, Elevation approximately 880’, with 3-7 mph left to right across the firing range.

Test groups, consisting of five shots each, were fired to obtain the smallest center to center group dispersion possible by adjusting the tuner. The SDT-1 Piezo Film was not placed in front to the muzzle. When two consistent groups were obtained measuring about .25 the SDT-1 Piezo Film was place at the muzzle. Image 1-1 shows a typical image.


Image 1-1
Image 1-1a provides an explanation of what the imagery represents. The time scale is the vertical lines with each line equal to 2 thousandths of a second and the horizontal line represent Root Mean Square voltage (RMS) and equates to energy. Long spikes mean more energy. The shooting events starts at the left side of the image on the A scale (upper). The lower scale shows the actual time the bullet exits the barrel/tuner. The sharp pike is the bullet actually hitting the piezo film


Image 1-1a

The follow is test group 1. , and oscilloscopes images. Group 1 was fired with the tuner at 230. Group 1a was shot with the tuner set at 200. The group dispersion is clearing evident.


The following is the image of both oscilloscope channels. The spike on channel B points (Blue) directly up to the vibration level occurring as the bullet exited the barrel. At the instant the bullet leaves the barrel the voltage, directly above the exit spike is at or near zero (line 2). Other information that can be directly obtained is the total firing event time, 4.24 ms (dX).

Image 1b

Below is the firing pattern for target group 1a (Lower target)

Image 1c

Image 1c clearly indicates the negative vibration spike, -.40 RMS at the instant the bullet leaves the barrel. The total firing time was 4.40 ms. These numbers were consistent through several test groups. This typical pattern shows the widest target group dispersal.

The following is Target Group 2 with tuner settings as indicated.




Image 2
Image 2 clearly shows the spike of channel B pointing directly to a zero voltage level on channel A. Computer enhancement shows a red X on line #2 positioned at the peak of channel B intersecting channel A at zero voltage. This is typical of small group dispersal.


Image 2a
Image 2a appears somewhat larger than the other because it was expanded so each horizontal line represents 1ms. The author did this for clarity as the A and B channels were actually overlapping graphically. The spike on channel B is pointing to of 0.80 volts on channel A. Again, this is typical of large shot dispersals.

The overall firing time of Target Group 2 was 4.32 ms for target 2 and 4.40 ms for target 2a.

CONCLUSION

The data collected indicates that when a barrel tuner is properly tuned the vibration level at, or near, the muzzle will be very close to zero at the instant the bullet leaves the barrel.


The overall energy level of vibration intensity does not correlate in any significant way to tuner settings.

Tuner settings do not appear to change the frequency of the vibrations.

Variances in ammunition quality significantly impact tuner setting effectiveness. While the tuner could be effectively adjusted to different ammunition's energy levels, the consistency was of singular importance. The author found no target ammunition that did not respond well to tuner adjustment.

Different ammunition does appear to change the intensity of vibrations.

Different ammunition does not appear to change the frequency of vibrations.

The most significant contributor to rifle vibrations appears to be induced by recoil energy.
 
Etal,

Hi Fred!:)

The barrel vibration debate is almost comical. It’s one reason I don’t post here any longer. I even stopped shooting… Too much BS near and far.

1) A barrel is not a solid chunk of steel - it’s a tube, and responds accordingly.
2) The dynamics of the tube (barrel) change as the bullet moves down the tube. No harmonics there! I proved that!
3) The energy produced by the cartridge induces the motion of the rifle (mostly recoil). (A barrel moves nothing like a vibrating solid chunk of steel – those vibrations start after the bullet has left the barrel.)
4) Adding weight to the barrel merely places tension and compression forces on the barrel that limit it’s ability to react - makes the muzzle motion more predictable. The motion of a barrel during firing has absolutely nothing to do with harmonic vibrations!
5) The whole idea is to make the rifle, including the muzzle, respond to recoil in a consistent manner, as much as possible.
6) The first motion of the barrel muzzle, upon cartridge discharge, is DOWN! The modulus of Elasticity will determine how the steel will react (It’s different for most steels). Too much weight and one will exceed the Modulus of Elasticity and the barrel will bend and stay bent! The theory is to apply just enough weight to approach the Modulus of Elasticity limit for that particular steel.

BTW a European target rifle manufacture confirmed my information with a similar study. Our studies were done independent of each other – no commingling of data whatever.

I can see no reason to bend a barrel down when it’s nice and straight. There are other approaches to controlling muzzle rebound that have been very effective over the years. A short stiff barrel of the proper length for the powder charge (tight bore at the muzzle helps) comes to mind… Any sporters out there shooting 250s?

Best,

WillH
 
Thanks Will for the post.
I have saved all your test info, lots of work and great information.
There has been some 250s shot with sporters this year, forgot who at the moment.

Fred K
 
Will H.

You wrote: "I can see no reason to bend a barrel down when it’s nice and straight."

I have seen that the inside of the bore is indeed curved, not straight, when indexing a barrel. I have also found that the best groups are the lowest groups during indexing. With that said, how does the internal curve in the barrel add up in the elastic models done be Varmint Al and others?

Also, i worked with a short Anschutz barrel, about 18.5" long, and while it did shoot some very impressive groups at times, it seemed to be too stiff, as if it were vibrating too fast, and scattered shots. I ruled out the rifle issues and such, and did pin this down on that particular barrel.

Does this make sense?

s??

s.
 
Steve,

What I’m referring to when I mentioned “bending” or "straightness" is:

Take any tube and clamp one end in a vice, then place a weight on the other end. The weighted end will droop! If you sight a rifle in without a “tuner” clapped to the muzzle it will register an impact point area. Add a weighted “tuner” to the muzzle and the impact point will be lower. Simple! I’ve done that many times! When was the barrel straighter – weighted or unweighted? Also, I think indexing a barrel is a great idea!

Most target barrels are straight to a fairly high definition of straightness. I think most shooters prefer their barrels to be as straight as possible. Well, it just seems to me that hanging a weight from the muzzle, which flexes the barrel down, is only one approach to limiting muzzle response to discharge. I’ve done the tuner thing…guess every shooter has. My point is that it just seems improper! Naturally, others will disagree.

I’ve had all sorts of barrels and found the least reactive to be air rifle barrels. I imagine because they are made from “soft” steel, too soft for use in cartridge rifles. It’s difficult to tune (via machining) a barrel to the cartridge and that’s why it’s not done too often. Plus, if the ammunition changes the barrel needs to be machined again.

I’ve had short heavy barrels that shot great! I’ve had short heavy barrels that didn’t! It’s takes time, and expertise, to tune a barrel for .22 RF ammunition. Guess tuners make the process easier…

I’m not bashing tuners! I just cringe at what some see as a harmonic connection with barrel tuners. I was caught up in that concept until I did a study and discovered my data didn’t support the hypothesis. My little examination convinced me there is no harmonic connection. Sure a barrel vibrates when it’s whacked with a hammer and after the bullet has “left the building”. Other wise I couldn’t prove the connection.

Actually, it’s kinda like “Global Warming”. Sure we’re contributing, but our activities are not causing the polar ice caps on Mars to melt, the red spot on Jupiter to split in two, or the sun spot cycles to change. Sometimes it helps to step back and really look at what is happening.

Best,

WillH
 
From WillH..
1) A barrel is not a solid chunk of steel - it’s a tube, and responds accordingly.
They both respond following the same laws. The only difference is a different moment of inertia and different weight. The fact that one has a hole down it's axis wouldn't change any of the things discussed in this forum.

From WillH...4) Adding weight to the barrel merely places tension and compression forces on the barrel that limit it’s ability to react - makes the muzzle motion more predictable.

Stresses in the barrel have no effect on how it reacts under added stress. They don't "limit it's ability to react". The added weight does not change "predictability", it only changes frequency and amplitude.


From Will H...Too much weight and one will exceed the Modulus of Elasticity and the barrel will bend and stay bent! The theory is to apply just enough weight to approach the Modulus of Elasticity limit for that particular steel

What you should have said is if you add too much weight you might exceed the yield strength - you can't exceed the modulus of elasticity. You couldn't "add weight to approach the modulus", you can't do anything but stay at the modulus as long as the properties of the steel remain the same.

Anyway Will, glad to see you posting here again. I always thought you offered a lot.


Steve B asked...With that said, how does the internal curve in the barrel add up in the elastic models done be Varmint Al and others?
Varmint Al's models accounted for barrel droop due to gravity but not curvature for any other reason.
 
Last edited by a moderator:
Pacecil,

I won’t be here long. Figured you’d reply. Hope you have been well.

Again, in the ideal test tube laboratory realm, it would be as you say. But…..

Example: A ¾” tube with a .22” hole down the center does not respond to stress and strain as a solid ¾ steel bar. One has less material. Me thinks….

The amplitude is exactly what is being limited by adding a tuner.

Young’s Modulus can be used to determine a type of material. True enough, but it’s application can be use to predict activity. As the application of stresses to strains increases at some point the material will not return to its original form… tends to bend and stay bent! Most materials have a unique modulus number! Agreed? The behavior of some materials as they near the yield point, for that material, movement becomes limited. Usually a yield point is just before failure. (Exclude lead) Every material testing graph shows this better than I can describe. Measure the stress and stain; divide the stress by the stain and you can determine the alloy – perhaps. Stressing a steel bar, as tuners do, applies tension to the top and compression to the bottom. It’s just loading!

Bottom line. The tuner preloads the barrel… result are the same, it flexes the muzzle down.

The whole idea is to consistently control motion produced during discharge. Harmonics don’t do diddly poo………..

This is like how long will a barrel vibrate? At sea level on Earth or outer space? Need to apply a dose of common sense.

Best,

Will
 
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