Bill's mantra on tuners

[ultramag44]

You're now telling me that my tuning condition, may or may not be affected by lubricity, temperature? That's pretty definitive.

You know what. I'm ready to say screw it, and just shoot.

Probably best to keep quiet, shoot a lot, and show up at a match with real results.

Gerry

I live in W. Texas, a very d-r-y climate. The moisture issue is not as pronounced here. I will say a wood stocked rifle that leaves a relatively wet climate and comes here will need the action screws tightened up in couple of days.

Another theory is warm wax (a barrel that just shot a round) vs cold wax (a barrel that has cooled while you watch the flags waiting for you condition to return) will cause a bullet to print to a different place due to the lubricating value being different. Another part of this theory is it will be more or less pronounced depending on what lube (what brand of ammo) is present.

Theory is great and the food of inspired conversation. But, as you say, sometimes ya just got to show up and shoot the match

Last weekend, I had no Intension of shooting my MTs-12 in the match. I had just finished sorting out the custom made (by me) scope base and bag plate (also made by me). I planned to test some Eley Edge in it after the match. I got the MTs-12 on Good Friday and have shot it very lityle so far.

The wind was running 21.6 mph w/ reversals. The flag and wind probe were doing a disco dance.

Long story short, I kinda got roped into shooting the MTs-12. Out of a clean barrel (6-groove, 1" diameter, 29" long) shot # one was center, but high, touching the edge of the 9 ring. Shot # two was a clean X!

Gerry, like you, I said, "Screw it!" I shot the MTs-12, I used Eley Edge, I watched the flag & probe and trusted the rifle. Yeah I won the match! I'm not such a great shot. What I did do was stick w/ the basics.

 

[AZUARO]

Your rifle is not in tune if it's shooting high after sitting for 2 minutes.

Try some more spots on the tuner and see if it changes. I don't know what barrel contour or length you have, just sounds like it isn't in tune.

I agree with Ken's statement, this has been my experience...

One other thing that I will add is that "Tune it and forget about it" seems to work well when you are using similar lots of ammo with close enough velocities...
I have experienced that if I switch to a higher/lower velocity lot with enough difference from what was used for the "Tuning", then it has been necessary to slightly readjust the original setting...The groups may not improve that much but the SWEET SPOT will and the shooting will not be as "Sensitive"...This is a reasonable statement as the higher or lower recoil/push of the bullet makes that barrel vibrate slightly differently.

It has always been my experience that a "Clean barrel" will need at least one or two shots (sometimes more) before going back to the "Sighting in" point (In Both: Rimfire and Centerfire)...It somebody has been able to shoot the same POI after cleaning the barrel, please post how you are doing it so many of us can learn from your expertise.

Regards,

AZUARO

 

[Vibe]

...This is a reasonable statement as the higher or lower recoil/push of the bullet makes that barrel vibrate slightly differently.

I'll agree with the observation of a given tune not fitting all velocities. But I can't say I totally agree with the above statement, after all a marimba key will sound the same note whether stuck soft or hard. No mater the impulse, the vibration is the same. In our case it's only the timing of exit vs the position of the muzzle that changes. Readjusting a tuner (of the designs in use today) doesn't alter this directly, but can help indirectly. The end result is you're doing the best you can with what you have (a rifle adjusted away from "tuned", instead of the best you can do, period. So long as tuners are a cylindrical weight that can only be adjusted for and aft, we will be stuck with that limitation.

 

[AZUARO]

Vibe:

When I said "Reasonable Statement" I quoted "Reasonable" meaning to say that that I didn't want to get into deep waters with internal ballistics/vibrations and that this statement
was "acceptable" for the sake of the discussion...

If I were to "Exaggerate" and not fully agree with you as you don't fully agree with my "reasonable" Statement , then:
You say: "a marimba key will sound the same note whether stuck soft or hard"
I then will ask: Would it sound the same "exact" note if you hit it with a steel rod and then hit it with a softer material such as plastic or wood?

Have you ever had a bad load (low powder) .22 RF cartridge that sounded very "weak" compared to the rest of the shots in certain lot?
Then, going to the extremes in .22 RF ammo: Would the shots "sound the same" and would the barrel "vibrate at the same" frequency firing a BB cap and then a .22 RF stinger?

.00190 sec is what it takes for a bullet traveling at 1050 ft/sec to leave a 24 inch barrel... .00187 sec when traveling at 1070 ft/sec...
This is the difference in velocity that I am talking about when I say that tuning is needed more for increasing the sweet spot than for possibly reducing the group size...
This very small difference in bullet exit "timing" is .00003 sec...How much would a barrel move in three one hundred thousands of a second?

If we use the term "Timing" are we implying that a tuner as we know them is capable of ACCURATELY "timing" something that happens in .00003 of a second?

Lets get a little deeper into vibrations of a barrel after it is shot, without really swimming in deep waters:
Vibrations go up and down (Whip) but the most important vibrations affecting us are the circular vibrations... If we only had up and down vibrations as is the general belief, then we would only have up and down shots (Vertical groups) and this is just not the case...The general belief of "Stopping" (TIMING) a barrel at an inflection point for the bullet to always leave at the same exact spot is only partially true.

Vibrations are a combination of the trigger sear releasing the firing pin and then the firing pin moving forward and striking the primer which also includes the cartridge being moved forward (part of the push that I meant in my reasonable statement)...Then we need to add the powder that begins to ignite and the initial bullet movement and engagement in the rifling...

Since there is a twist on the barrel (rifling), the bullet while moving forward will spin and will create some measurable torque together with a circular vibrational pattern, or arc..The larger the barrel the larger the arc and the heavier the barrel the lesser the arc...Then we have that the heat of the burning powder combined with pressure wave generated by the expanding gasses generate another vibrational pattern that is induced into the barrel.
All of these movements cause the barrel to stress and to generate up/down/circular motion vibrations...

Having said this, I don't know about you and other shooters, but I sincerely don't believe that barrels shooting different loads will vibrate identically...
The way I understand and see it is that a tuner is matching the vertical oscillation of the barrel to the exit of the bullet at an inflection point as good as possible... YES....But it is also taming the rotational vibrations (Dampening) by adding MASS to the barrel...

You know me as we have cordially discussed many other issues in the past, I am not sarcastic by any means but let me ask you: Do you now understand why I used a simple "REASONABLE STATEMENT" phrase trying to avoid all of these complications that will undoubtedly open a can of worms that will in turn deviate the topic of the thread as well as my very simple answer/experience that I was trying to pass?

I agree with your remarks: "We do the best with what we currently have"...

Regards...

AZUARO

 

[Vibe]

You know me as we have cordially discussed many other issues in the past, I am not sarcastic by any means but let me ask you: Do you now understand why I used a simple "REASONABLE STATEMENT" phrase trying to avoid all of these complications that will undoubtedly open a can of worms that will in turn deviate the topic of the thread as well as my very simple answer/experience that I was trying to pass?

I agree with your remarks: "We do the best with what we currently have"...

Regards...

AZUARO

Sure. I understood it the first time. In this instance it's being used in much the same way that politicians use it when they speak of "Reasonable" gun control laws. My point is that vibrating systems are not governed by the striking, or initiating event - but rather by the restoring forces - which do depend upon things that do not change from shot to shot.

 

[mks]

.00190 sec is what it takes for a bullet traveling at 1050 ft/sec to leave a 24 inch barrel... .00187 sec when traveling at 1070 ft/sec...
This is the difference in velocity that I am talking about when I say that tuning is needed more for increasing the sweet spot than for possibly reducing the group size...
This very small difference in bullet exit "timing" is .00003 sec...How much would a barrel move in three one hundred thousands of a second?

It would take 0.0019 sec if the bullet instantly accelerated to 1050 ft/sec. It actually takes about twice as long. Regardless, your main point is correct that the difference in exit time is small, about 0.00006 sec.

If we use the term "Timing" are we implying that a tuner as we know them is capable of ACCURATELY "timing" something that happens in .00003 of a second?

Yes, absolutely. We want the muzzle to be pointed upward more for the slow bullet that comes out later, so that it strikes the target at the same elevation. After all, if you knew that the muzzle velocity of your next shot was going to be lower, you would compensate by aiming higher, right?. Tuning means getting the rifle (not just the barrel, but the whole system) to do this automatically. From the bullet exit time difference and the needed muzzle angle difference, the muzzle rotational velocity necessary to accomplish this can be calculated. The sweet spot is the portion of the waveform over which the rotational velocity matches as closely as possible that necessary for positive compensation.

Cheers,
Keith

 

[Vibe]

It would take 0.0019 sec if the bullet instantly accelerated to 1050 ft/sec. It actually takes about twice as long. Regardless, your main point is correct that the difference in exit time is small, about 0.00006 sec.
Cheers,
Keith

Determining the exact value of these times is a bit problematical. His estimate assumes instantaneous acceleration, yours would tend to indicate constant acceleration. Neither is "exactly" correct. In fact one of the issues that tuning cannot compensate for is a variation in acceleration curve between 2 rounds. If one round accelerates faster, but doesn't reach the top speed of the next round. Both may exit at exactly the same time in barrel, but with differing muzzle velocities. Or worse yet, exit at differing times, but with the exact same muzzle velocity. Only a well tuned rifle shooting over a very accurate chronograph would tell this though.
Looking at the muzzle velocities of short barreled pistols (Like the NAA 22 revolver with a 1-1/8" barrel) indicate about 700 fps is reached in that length, with quite a bit of variation between brands. I'm pretty sure Eley of any type was not tested though. But the point is that only the remainder of the acceleration is really powder burning, the biggest part of the initial push is primer powered. It's somewhat amazing that we've accomplished the low levels of variation that we currently see. A little bit of primer difference goes a long way.

 

[mks]

Vibrations go up and down (Whip) but the most important vibrations affecting us are the circular vibrations...

To my knowledge, there is no experimental evidence to support this. There are some measurements of cannon muzzle motion that show strong circular motion, but cannon typically have recoil systems that allow the barrel to travel backwards, which reduces forces that cause the up/down whipping motion. A BR barrel, on the other hand, is firmly attached to a stock that places the center of mass of the rifle significantly below the bore. Thus there is a strong moment to cause up/down. Until we get two-dimensional measurements of BR rifle muzzle motion, we don't know for sure, but I expect the consensus that up/down motion is strongest is correct. (But I could be wrong.)

If we only had up and down vibrations as is the general belief, then we would only have up and down shots (Vertical groups) and this is just not the case...The general belief of "Stopping" (TIMING) a barrel at an inflection point for the bullet to always leave at the same exact spot is only partially true.

The focus on up/down motion is not only because it is likely the strongest, but also because vertical dispersion due to different bullet exit times is the only effect that we can compensate for (by having the bullets exit when the muzzle angle is rising at just the right velocity). All the other components of barrel motion we would ideally like to be zero. As you try your tuner at different positions, you may find a spot with decreased vertical dispersion, but increased horizontal dispersion. The best tuner position is where horizontal (and circular and all other components of) muzzle motion is minimized and vertical motion is "just right."

 

[mks]

Determining the exact value of these times is a bit problematical. His estimate assumes instantaneous acceleration, yours would tend to indicate constant acceleration. Neither is "exactly" correct. In fact one of the issues that tuning cannot compensate for is a variation in acceleration curve between 2 rounds. If one round accelerates faster, but doesn't reach the top speed of the next round. Both may exit at exactly the same time in barrel, but with differing muzzle velocities. Or worse yet, exit at differing times, but with the exact same muzzle velocity. Only a well tuned rifle shooting over a very accurate chronograph would tell this though.
Looking at the muzzle velocities of short barreled pistols (Like the NAA 22 revolver with a 1-1/8" barrel) indicate about 700 fps is reached in that length, with quite a bit of variation between brands. I'm pretty sure Eley of any type was not tested though. But the point is that only the remainder of the acceleration is really powder burning, the biggest part of the initial push is primer powered. It's somewhat amazing that we've accomplished the low levels of variation that we currently see. A little bit of primer difference goes a long way.

Vibe,
Agreed. I am guilty of simplifying to not obscure the main point.

Yes, the powder charge in a 22RF is so small that several other factors become significant that are much less so in centerfire. It is a challenging cartridge to make shoot well.

Cheers,
Keith

 

[Vibe]

Vibe,
Agreed. I am guilty of simplifying to not obscure the main point.

Cheers,
Keith

As are we all. It's almost a requirement when dealing with this subject that we have to take several simplified partial approaches vs a single all inclusive "solution". Your previous post to AZUARO more or less reinforces my thinking that future tuner designs will have to be able to tune timing, vertical moment, and horizontal moment all independently instead of just threading a cylindrical weight fore and aft. The timing issue may also require some variable action tuning in addition to "just" muzzle and barrel tuning (Jeffrey Madison has done some interesting work on this). Since the action is where the majority of the restoring forces originate.

 

[tim]

I'd bet against it. The one area constantly missed or minimized by the "vibration theory " guys is our old friend " interior bore characteristics" and its relative import on the equation.
Now friend Vibe has somewhat mischaracterized what I've said in the past by inferring this is the single most important deal.....which it is not IMHO. This started as a response to former guru M Hammonds, which if we all remember, was once of the opinion that he could tune anything to win matches, and/ or its all about the contour....wrong and away wrong. The initial comments were essentially that without certain critically important characteristics, your done before you start. These characteristics have been opined on by several builders.
Now the point to this whole thing is that some, not all but some, hard working barrel guys are turning out stuff that is very consistent, using repeatable principles, mostly involving interior dimension and quality taper lapping to get us closer to where we need to be. This also has taken out a lot of the gross variables in tuning.
Why , do you suppose, a couple of the better guys can set tuners to a narrow range, right from the start, in some cases pre-setting, never to change again.
The incremental steps are getting smaller and at the end of the day were still dealing with moderate variables that may never be dialed out entirely