Tuners some info.

[mks]

MUZZLE & TUNER AT EXIT.... This picture shows the orientation of the muzzle at the time of bullet exit, approximately 0.00092 seconds. It is pointing upward and the projection to the 100 yard target is still climbing. The projection stays near this position for about 0.0001 second. See the charts below.

Keith
I think you are misreading table 2.You want the barrels muzzle climbing at the time of bullet exit and table 2 shows the droop caused by gravity coupled with the rise for each velocity.The faster shots appear lower because the barrel hasn't risen as much as the slower shots due to more barrel time.The muzzle is still rising.
Waterboy aka Lynn

Lynn,
In the text you quoted, note Al says the muzzle is "pointing upward" and the "projection...is still climbing." He did not say that the "muzzle" is climbing.

Farther down the page:
SIMULATED 100 YARD TARGET.... This graph summarizes the data by showing where the barrel is pointing at the 100 yard target at the time the bullet exits the muzzle (top row). The bottom row shows where each bullet would strike the target by including the bullet drop due to the bullet's flight and the drop due to the downward velocity of the muzzle as the bullet exits.

The title of Table 2 is:
Table 2: Bullet Drop due to the Muzzle's Downward Velocity at the Time of Bullet Exit

In Table 2, columns 4 and 5, the "muzzle vertical velocities" are all negative, and are more negative for the slower shots (the wrong direction for compensating for slower bullet velocity). Columns 6 and 7 show that where the bullets strike the target (due to the downward velocity of the muzzle) drops for the slower shots.

The title of Table 3 also includes Downward Muzzle Velocity.

In the text below Table 3:
ADDING IT ALL TOGETHER.... Here are the results for the two Light Rifles firing the same five shot pressure curves. After including where the muzzle is pointing at the 100 yard target, the bullet drop for each shot's muzzle velocity, and finally the downward velocity of the swing of the muzzle as the bullet exits...

You can think of the barrel like cracking a whip. As the wave travels from the action to the muzzle, the muzzle first points slightly downward as it rises and reaches its highest position. Then it points upward as it falls. There is a phase lag between the muzzle angle and muzzle position.

Cheers,
Keith

 

[mks]

Is the reverse taper used on RF barrels. I am just getting into this but I was told that barrels are tuned on RF Sporters by taking small amounts off the reverse taper portion until "Tune" is achieved. Has anyone experimented with Reverse Tapered CF barrels?

Pete,
I am interested in this, too, but reverse taper barrels for CF would be illegal unless they fit within the "forward" taper contour, which would make them really thin. A rule change would be nice to allow shooters more flexibility to try things like this.

Cheers,
Keith

 

[mks]

... that old middle of the road at best barrel won its last match at 200 with a .291. ...

Interesting. Increased flexibility near the muzzle could be the next big thing in tuning rifles.

Cheers,
Keith

 

[Lynn]

Keith
Al is giving you the whole cycle in his examples.He lists were you want the muzzle going for best accuracy and that is up.

If you look at the model of my rifle on his website it appears that the barrel is too long and that the accuracy is suffering or on the down swing.That same rifle shot 3 world records as it was modeled.

The muzzles downward velocity is caused by the muzzle being pointed up.
Lynn aka Waterboy

 

[mks]

My forend is simply a three inch wide milled aluminum block that bolts directly to the barrel.

Gene,
If I remember correctly, the Davidson forend clamped between the action and the barrel like a recoil lug. What I was thinking of was something more like your design that clamps on the barrel. The way it would be different would be that it would clamp near the action, and the plate would extend farther forward. Two clamp halves and a attached plate 3" wide and about 16" long. One could try different plates, say wood, fiberglass and aluminum, of different thicknesses to see if any improved tuning.

There is some suggestion that this might work in that some shooters tune by how far they place the front of the forend past the front rest. Varying this position changes how forend motion gets transmitted to the muzzle.

Just another wild idea,
Keith

 

[Butch Lambert]

Keith,
A reverse taper barrel is legal in centerfire. I chambered one and gave it to Jay Lynn Gore and he shot it very little. He said it showed real promise, but went on to other things. Pat Byrne has one that he has not chambered yet.
Butch

 

[Boyd Allen]

Varmint Al showed three different ways to end up on the left side of the curve, weight added at the muzzle, a longer (24") barrel, and thinning the barrel down some in the middle. I believe that a reduction in diameter near the center of the barrel would reduce optimal tuner weight. Not that rimfire barrels contours can be directly applied to centerfire, but one picture in PS, of a Calfee pistol, shows just such a center of barrel reduction. I believe that the reason that he did this was for balance, because it allowed him to fit a lighter tuner. As we all know, 10.5# CF Benchrest rifles also have balance issues when considering barrel weight as combined with a tuner.

 

[Roy Allain]

Pardon if this was addressed already

but I just came in on this thread.

My thoughts on this may be way off, but here is my take on this.

Someone mentioned that the .030 expansion of the barrel length is too much. It should be much shorter. I don't think it makes much even if it was longer.

.030 expansion over the length of a 20" barrel is roughly .0150 per inch of barrel. I don't think it means very much in terms of what a tuner does or cannot do.

Please correct me if I'm wrong.

Thanks

Roy

P.S.: Gene, I'm sending a PM shortly.

 

[Boyd Allen]

When one looks at how little tuner adjustment it takes to go from node to node, and that barrel growth would seem to produce a situation similar to turning the tuner out, it just may be significant.

 

[Pete Wass]

In a conversation

with a certain well known RF Gunsmith he mentioned that it does indeed make a difference where a rifle sets in the bags, both front and rear as to how accurately a rifle shoots. I won't relate the story of his discovery of this but I found it interesting.

Perhaps this is more true with RF rifles becaues of barrel time but I don't know. Some of the best 6 power shooters on the Planet shoot without a front stop, thus using the slope in the buttstock for elevation changes. Dunno what to think

 

[HuskerP7M8]

Gene,
If I remember correctly, the Davidson forend clamped between the action and the barrel like a recoil lug. What I was thinking of was something more like your design that clamps on the barrel. The way it would be different would be that it would clamp near the action, and the plate would extend farther forward. Two clamp halves and a attached plate 3" wide and about 16" long. One could try different plates, say wood, fiberglass and aluminum, of different thicknesses to see if any improved tuning.

There is some suggestion that this might work in that some shooters tune by how far they place the front of the forend past the front rest. Varying this position changes how forend motion gets transmitted to the muzzle.

Just another wild idea,
Keith

Keith,

Something similiar to this or other variations shouldn't be too difficult.
Here's a modification Joe Friedrich did to his Ultralight stock.

Landy

 

[pacecil]

Probably the last post of Roy Allain is typical of what has been happening in this thread (.030 expansion in a 20" barrel is .0015 per inch, not .015). People keep coming up with all sorts of numbers concerning what happens with barrels and tuners that are simply wrong. The whole thread was started with a wrong number (a barrel expands .007 not .030 when heated 50f).

Then there are all sorts of claims as to what a tuner does to group size as you adjust it in and out by a few thousandths. Varmint Al showed this to be effect to be essentially zero but that was based on his computer model so it won't treated as indicative of what happens in the real world. Unfortunately Beggs or no one else has given any better numbers we might rely on.

There has been discussion of how weight or temperature of the column of air in the barrel will affect accuracy, but that was later sort of changed to how it might be barrel temperature that is the cause, but I think it was then decided that temperature change just wasn't enough to have much affect on accuracy, so I have to say at this point: there seems to be a lot of confusion going around!

Varmint Al's work was pretty clear but that seems to be twisted around and misunderstood by a lot of people so this has added to some of the confusion. It seems now that this thread has become so garbled up that I think we are going to have to just start over - kinda like with healthcare!

 

[mks]

Keith,
A reverse taper barrel is legal in centerfire. I chambered one and gave it to Jay Lynn Gore and he shot it very little. He said it showed real promise, but went on to other things. Pat Byrne has one that he has not chambered yet.
Butch

Butch,
That is good to hear. I am confused, though, because the IBS rulebook says this: "a diameter at and not more than 5 inches ahead of the bolt face of not more than 1.250 inches and a diameter at any point between the muzzle and 5 inches in front of the bolt face not greater than would be defined by a straight taper between such point 5 inches in front of the bolt face at 1.250 inches diameter and the muzzle at .9 inch diameter at 29 inches." This seems to dictate the small end at the muzzle

Keith

 

[mks]

Keith,

Something similiar to this or other variations shouldn't be too difficult.
Here's a modification Joe Friedrich did to his Ultralight stock.

Landy

Landy,
That's it! Any results with different forend stiffness?

Cheers,
Keith

 

[Butch Lambert]

Keith, as long as it fits in the drawn profile. Draw the picture they are describing in the rule book. Anything that fits inside those lines are legal.
Butch

 

[mks]

Keith, as long as it fits in the drawn profile. Draw the picture they are describing in the rule book. Anything that fits inside those lines are legal.
Butch

Cool. So you're saying that the 1.25" end can be at the muzzle?

Cheers,
Keith

 

[Lynn]

Pacecil
Maybe you can clear up some of the confusion?
For best accuracy do you want the bullet to exit the muzzle on the upswing or downswing?
Is the muzzle deflecting downwards when the bullet leaves? and why is it deflecting downwards?
Does adding or changing the weight of the tuner make all the difference in the world? or does it really matter as long as you make weight?
Does moving the tuners weight in or out a thread change the amount of weight as seen by the muzzle? In other words can you put a 1 pound weight on your outstretched arm and get the same affect as placing it on stick 10 feet away?
Did Varmint Al think tuners were a plus or a waste of time?
If you can put two bullets through the same hole at 100 yards with a 8 grain variation in the powders charge weight(300 Ackley) is that huge variation in grouping ability associated with the weight of the tuner or is there some other factor we are not seeing?
If I am getting 3/4 of a bullet hole worth of vertical at 100 yards using a 308 bullet and turn my tuner 1/4 turn and get one hole groups what caused that to happen?
If it is repeatable and it is why is that?
On your guns with tuners what are you seeing with regards to group sizes while adjusting your tuner and is it in front of or behind the muzzle? and what if any difference can we expect to see between the two positions?
Waterboy aka Lynn

 

[Butch Lambert]

No,
It can be no larger than the stated muzzle size, but it can taper back from that dimension in a reverse taper toward the breech.
Butch

 

[Gene Beggs]

but I just came in on this thread.

My thoughts on this may be way off, but here is my take on this.

Someone mentioned that the .030 expansion of the barrel length is too much. It should be much shorter. I don't think it makes much even if it was longer.

.030 expansion over the length of a 20" barrel is roughly .0150 per inch of barrel. I don't think it means very much in terms of what a tuner does or cannot do.

Please correct me if I'm wrong.

Thanks

Roy

P.S.: Gene, I'm sending a PM shortly.

Roy, I don't use the PM function here on the forum. I prefer an e-mail. genebeggs@cableone.net

In response to your post above, I know for a FACT that it takes .018 movement of my four ounce tuner in either direction to throw the rifle completely out of tune, assuming of course it was perfectly in tune to begin with.

George Ulrich found there was considerable growth in length of a 24 inch barrel when heated to 120 degrees F. (How's that Pacecil?)

George's initial measurements showed a .030 increase in length with approximately a 50 degree increase in barrel temp. Some have questioned the .030, claiming that according to calculations, it should be much less but they were not there and I doubt they have actually duplicated the setup that George used and actually measured the increase in length. In the real world, things don't always work out like they do on paper and in computer generated models.

George said he stood the 24 inch barrel on a granite surface plate and made his measurements with precision instruments, both temp and length. George is a very competent and knowledgeable tool and die maker and I would be very cautious about questioning his results. Regardless of how much the barrel grows in length, we can all agree it grows SOME. (How's that Pacecil?)

We can argue about technicalities, numbers, theories; we can speculate about this and that and go on and on forever but the only way to PROVE you know what you're talking about is to demonstrate it with an actual rifle and tuner in the real world. I can do that; can you?

My tunnel is always open to those who can prove me wrong about anything I have said. And Roy,, please understand I am not trying to be a smart a$$ and I'm not refering to you personally.

Gene Beggs

 

[Gene Beggs]

I'll try to be as nice as i can.

Probably the last post of Roy Allain is typical of what has been happening in this thread (.030 expansion in a 20" barrel is .0015 per inch, not .015). People keep coming up with all sorts of numbers concerning what happens with barrels and tuners that are simply wrong. The whole thread was started with a wrong number (a barrel expands .007 not .030 when heated 50f).

(GB) Pacecil, were you there? Did you witness the experiment? In the real world, things don't always turn out as they do on paper and in computer generated models. Let's not nitpick the numbers to death; who cares? Regardless of how much the barrel actually grew, we can all agree it grew some; how's that?

Then there are all sorts of claims as to what a tuner does to group size as you adjust it in and out by a few thousandths. Varmint Al showed this effect to be essentially zero but that was based on his computer model so it won't be treated as indicative of what happens in the real world. Unfortunately Beggs or no one else has given any better numbers we might rely on.

(GB) Whoa, whoa; hold on there Smokey, I can give you some numbers you can rely on! And I can tell you exactly what happens when you give my tuner a half turn, and I can tell you exactly how far it moves and I can tell you exactly where to place it when the ambient temperature increases to X degrees. I don't just throw out numbers and statements based on speculation; what I say, I have proven in the real world in actual conditions. I have come to have great respect for Varmint Al and his work but regardless of what his computer generated models show, I know for fact what happens in the real world.



There has been discussion of how weight or temperature of the column of air in the barrel will affect accuracy, but that was later sort of changed to how it might be barrel temperature that is the cause,

(GB) Bull! I never "sorta' changed" anything I said. I assure you, it IS changes in air density (weight) that causes our rifles to go out of tune, not barrel temperature and the reason you do not understand this is because you have never piloted highspeed aircraft. You have no appreciation for the enormous force of air at mach 2.7.


,,but I think it was then decided that temperature change just wasn't enough to have much affect on accuracy, so I have to say at this point: there seems to be a lot of confusion going around!

(GB) There may BE a lot of confusion going around but not on my part. I know what I'm talking about. It is not speculation. I shoot; a lot, and I shoot in competition in the real world. I'm not an armchair rifleman.


Varmint Al's work was pretty clear but that seems to be twisted around and misunderstood by a lot of people so this has added to some of the confusion. It seems now that this thread has become so garbled up that I think we are going to have to just start over - kinda like with healthcare!

(GB) Pacecil, I agree with you about starting over on healthcare but not about starting over on this thread. We've made a lot of progress. The only thing I've heard from you is, "No, that won't work, No that isn't right, and according to my calculations ,,,,blah, blah, blah." Let me ask you something; Do you shoot or do you just figure and talk?



Pacecil, you're a real piece of work, but I still love ya' man!

By your own admission, you are a mean, nasty recluse, but you serve an important purpose; you keep us all honest.

My comments to your post above appear in bold, preceeded by (GB)

Later,

Gene Beggs