An idea regarding accuracy

[slm9s]

This may be useless nonsense, ye be warned.

My understanding is that accuracy nodes occur due to barrel harmonics, or whip. Just because one theoretical load shoots the exact same velocity every time doesn't mean it will be the most accurate due to harmonics. This occurs due to the force/velocity of recoil being brought to zero by the force of the shooter's shoulder and the stock which is attached to the action. Because the rifle's stock is attached mainly to the bottom of, and is lower than the rifle's action, the rifle's force/velocity toward the shooter is not in the same vector as the shooter/stock stopping the force/velocity of recoil, its above it. This causes an upward force during recoil that creates barrel whip/harmonics. If you've ever shot full auto, or a big boomer; you're familiar with muzzle rise.

Now, imagine a top loading, drop port single shot action. If we took such an action and had action screws on the left and right side attaching a stock that was directly in line behind the action, could we eliminate the upward force creating the barrel whip that renders many loads inaccurate? Or at least reduce it? If the action and stock is coming direclty backward and not up, it would seem that the rifle would have little barrel whip.

You'd need TALL scope rings, but that's been done before.

Thoughts?

 

[22BRGUY]

I don't think I can agree totally with your premise but know I could well be wrong. What I believe is that the "whip" of the barrel is determined by many things rather than just the bedding screw placement. What comes to mind is the incidence where a heavier powder charge can sometimes shoot lower than a lighter one for example but appreciate your thinking about this theoretical idea and look forward to the response of others on this.
Best Wishes

 

[slm9s]

Again, this could be nonsense, but could that not be explained by the barrel being at a phase of "whip" where the muzzle was below the true bore axis with the heavier load?

In my mind, the trigger is pulled, the primer/powder go band, the barreled action attempts to move straight backward since its pushing the bullet straight forward. But the movement is instantly being reduced by the stock which is attached/positioned below the action. Hence a thousandth of a second after the "bang", the action moves mainly backwards, but also "up" a thousandth of an inch, and it takes another thousandth of a second for the muzzle end of the barrel to move up - creating barrel "whip". Different powder loads will have the bullet leave the barrel in different portions of this whip.

Now as to whether accuracy nodes occur when the barrel is at either the top or bottom of the whip, vs in the middle, I'm not sure. . . 8)

 

[338 Mollett]

The barrel will flex up and down from being a stationary barrel subjected to force it will also torque due to the bullet going down the barrel under force.There is also a shock wave that travels the length of the barrel a few times before the bullet leaves the barrel,while all this other is going on at the same time.Load development I think is a separation of shock wave and bullet at the muzzle at the same time.

 

[Terry]

I thought a properly balanced gun, setup properly in the bags, would generally recoil straight back.
It was my understanding that if it jumped up, it was setup wrong.

Ready to be educated.

 

[CatShooter]

There is also a shock wave that travels the length of the barrel a few times before the bullet leaves the barrel...

This would be very easy to document if it happened, but it has NEVER been demonstrated, so as it stands right now, it is a myth.

 

[jonbearman]

I will be watching this as this is really interesting.I think the kelbly club and others are trying to improve the balance of this inline idea.Think about the unlimited rail guns.They are as firm and inline as can be with barrel whip.Now they do shoot fantastic but the human interaction is hard to rule out as part of the problem.

 

[LHSmith]

If you are thinking along the lines of a Rail Gun (a.k.a Heavy Bench, Unlimited) as used in short range BR, a quick look at the match results will show that a LV or even Sporter class bag gun will sometimes shoot a lower winning agg than the winning Rail Gun. There really is very little difference separating the aggs between all the classes if you make the comparison based on 5-shot group matches. (Some Unlimited matches run 10 shot groups).
As was said, any bench gun in SR BR MUST be balanced in order to be competitive....it better not rise off of the front bag or your toast.
In any event, there is no remedy for controlling bbl. harmonics, other than tuning with loads or a tuner.

 

[M14AMU]

It also comes about because a whole helluva lot of folks don't know how or what constitutes a good position!!

 

[savagedasher]

35 to 40 years ago Ljtic made a space shot gun smooth bore. It was like a broom stick with a butt plate. It was butt ugly but it recoiled straight back. Rifles have a twist bore so they have spin or twisting motion. How much or what effect it has is all part of making a gun shoot. I do know a butt plate that is farther from the center of the bore lifts more. Larry

 

[broncman]

For every action...their is an opposite reaction...

A butt plate below the bore creates a torque arm pivot point. Rise created by recoil is a component of recoil vs bullet time in barrel. More barrel time, as in heavy slower bullets, recoil creates rearward movement before bullet leaves the barrel..

Barrel "whip" due to straightening under pressure has another component of rise...

It is all a symphony, and you are a the conductor! Shoot the heavies and you will see how important gun handling and straight back recoil are...

I am no Beethoven with the 215's in FTR....

 

[BoydAllen]

Harold Vaughn wrote Rifle Accuracy Facts. I gather that most, if not all of you have not read it. I recommend it to you.

 

[Killshot]

Harold Vaughn wrote Rifle Accuracy Facts. I gather that most, if not all of you have not read it. I recommend it to you.

Best book on the aspects of accuracy I've read.

I doubt OPs premise. The harmonic vibration of the barrel occurs regardless of what the action sits in.

Don't confuse recoil-rise with barrel harmonics and their effect on nodes.

 

[338 Mollett]

I killed time one night while wife was watching dancing with bullfrogs or some crap,and took a barrel that was out of the action and laid it on a support that would not hinder vibration.I tapped the barrel with a hard rubber hammer and observed the vibrations.It was like a tuning fork.I ran my finger down the barrel while still tapping and found something strange there were places in the barrel where the vibrations were greatly reduced.Now I know a barrel acts like a garden hose when you turn the water on holding back from the nozzle and when twist is injected it will torque.Thus most of us use stiff barrel contours to reduce the fliers so to speak.But those vibrations I believe are shock waves.After shooting the 338 heavies a lot,I,m convinced the reduction of these forces has much to do with repeatable accuracy.

 

[BoydAllen]

Even with a top to bottom balanced rifle, with the recoil taken on a line with the bore, there will be barrel vibration because that starts from the gravity sag of the barrel straightening out, and over swinging do to inertia, from the pressure behind the advancing bullet.... but the amplitude with be significantly reduced. Vaughn devised a bedding block that had vertical leaf springs attaching it to the stock, with enough travel so the recoil lug did not hit anything until the bullet was out of the bore. He also did an experiment with a rail gun, adding weight above the bore to balance the sliding part with the barreled action around the bore. He used instruments to measure muzzle movement in both configurations. Like I said, get a copy and read it. It may be a new thought to the OP but Mr. Vaughn did an interesting investigation along those lines some time back.

 

[LCazador]

Wow!! There have been barrels completely bedded and actions floated, and actions completely bedded and barrels floated! Nothing works perfectly because the guy behind pulling the trigger is the bottom line. IMHO barrels do not flop up and down like in the cartoons! The harmonics are up, down, and all around, and they are minute! Things like bedding, trigger vibrations, striker springs, bolt vibrations, action stiffness, barrel stiffness and all harmonics, all come into the picture. Lest I forget the guy that put all the fodder together that is fed into these superb shooting machines!! I think the benchrest guys have the solution for all of this, that is eliminate as much of this as you can by trial and error, and when you run out money trying everything, start looking at yourself 8)!!!

 

[slm9s]

Wow!! There have been barrels completely bedded and actions floated, and actions completely bedded and barrels floated! Nothing works perfectly

Wow!! Who said something was going to work perfectly? I was just putting out an idea that MIGHT reduce ONE FACTOR of what determines accuracy. Quite a jump to think something was going to be PERFECT.