finding an "accuracy node".

[in2deep]

That must be similar to that PPC guru that said he could actually "feel" the gun recoil differently when it was out of tune.

 

[FroggyOne2]

I listen to my rifles when I am shooting, I can tell a lot of times something different, with the statement "Oh, that ain't going to be good".

 

[mlove]

finding an accuracy node

Fantastic thread. Using this to workup some new loads for the season. Thank you.

- Miles

 

[RDavies]

Ive wondered if the idea that rimfire Benchresters had that you could hear the difference when a rifle was realy in tune had any merit? Experiencing a similar thing recently with a 6.5 WSSM brought the discussion up with some local shooters??????

 

[M14AMU]

Here's a method I've used for 60 years now!

When all my bullets hit where I desire at 1000 yards....I know I'm home free!

 

[seymour fish]

The OP's notion that Chris Long's theory addresses bullet seating depth escapes me. I think Chris is addressing the transmission of a shock wave, and arguing that it dilates the bore as it travels, and that the worst place to have that bulge is at the muzzle when the bullet exits. If you synthesize this notion with the Purdy RX, which Many have found to work, are you not coming at the same issue? Quickload barrel times, typically with a plus or minus fudge factor applied, and perhaps with MV matched to chrono proofs via tweaking the BA, using the OBT times-for-lengths saves a lot of powder. In rimfire, the tube length tweak is available, and instead of tipping the powder can, different lots/speeds of ammo May accidentally hit a proper barrel time empirically. Analogous to tuning a header to a motor for best volumetric efficiency at a given rpm range. None of this likely has anything to do with 'positive compensation' due to barrel whip, etc. Seymour

 

[40X Guy]

I found the accuracy node in my first 6 Dasher pretty quickly using the OCW method 2 years ago. I have always ran the same powder charge, have kept a very accurate round count, (708 rounds) and have always seated the Berger Hybrids @ .010 off the lands as the lands have eroded right at .011 since gun was new. But I' m wondering if as the lands wear does the gun move out of its node as the seating length is now longer? Any insight on this? Gun still shoots pretty well and i won a relay with it this past saturday but i am wondering if I should change up anything...

Frank

 

[dmoran]

Frank -
I will suggest that every barrel can be different, and the only true way to find out for your barrel is to test.
I have a barrel where "chasing the lands" doesn't improve much at all. But another where it means a whole bunch.
Bullet shapes, lead angle, etc.. no doubt play a role in all this as well.
Donovan

 

[CatShooter]

Chris Long wasn't referring to barrel vibration but rather a "swell" that travels up and down a barrel. A LARGE number of shooters have had good results using his theory.

The big problem is that "IF" there is a swell that travels back and forth in the barrel, they would show up with a pressure strain gauge....

... and they do not!!

This has been a shaky theory for many many years, and there is no science to it.

 

[dedogs]

Catshooter,
Not trying to start an argument but I'm curious as to what you would attribute the success people have had using this method of OCW?

 

[Raythemanroe]

Catshooter,
Not trying to start an argument but I'm curious as to what you would attribute the success people have had using this method of OCW?

Not to butt in but the method is sound, but maybe the theory isn't.. You are still tuning your bullets to your guns harmonics, but your not ladder testing.. Very similar vertical powder tune and horizontal seating depth.. Hi road vs the low road..

Ray

 

[Steve Blair]

The big problem is that "IF" there is a swell that travels back and forth in the barrel, they would show up with a pressure strain gauge....

... and they do not!!

This has been a shaky theory for many many years, and there is no science to it.

[br]
I am interested to know what strain gauge testing you've done in this regard. That is also what I thought would provide a definitive answer. If the "swell" was sufficient to cause an accuracy effect, it would produce a measurable change on a strain gauge. The other requirement would be an adequate sampling frequency to fully capture the event, if present.

 

[dedogs]

Ray,
Not saying the method is not sound, it obviously is or no one would be using it. I would simply like to know what Catshooter would possibly attribute the method's success to if not timing the barrel bulge frequency. Just curious is all.

 

[Raythemanroe]

I think something is being timed or tuned but if it's a swell or vibration I don't care as long as the results are the same... I see Catshooters point, unless you can measure it


Ray

 

[CatShooter]

Catshooter,
Not trying to start an argument but I'm curious as to what you would attribute the success people have had using this method of OCW?

Not trying to argue back.

Lookie, in shooting we change a lot of things. Even when we think we are only changing one thing, lots of other things change as a result of our changing "One thing".

You change the seating depth and that is all... but as a result, the timing of the rifling engagement changes, the time in the barrel changes, even if it is only a bit - the vibration pattern of the barrel changes, and the exit time of the bullet in the vibration cycle changes... all by just changing the seating depth.

Now, you change something and it looks better, then you make up a reason, cuz you "think" it makes sense (to you) and you write about it on your website cuz you have an official theory - that does not make it true. To make a "Real theory", it takes tons of technical testing and challenging, even to the point that you test in a way to disprove your silly self. NONE of this has been done here (or in the other "theories", like ladder and OCW, and bullets that travel off axis and find their way back).

There are a lot of "Theories" in shooting that are so scientifically impossible, that you could do a book on them. This is one of them.

It is so easy to prove or disprove - look at the strain gauge scope trace of a pressure gun... there should be five or 6 short, tall, "blips" super imposed over the main trace of this magical wave bouncing back and forth... but there is none.

 

[dedogs]

Not trying to steal the thread, but it seems with all I've read here that it could be said that bullet seating could be the most critical part of load deveopment for accuracy hence the reason it seems to be the last step in all the load development "notes" I've read.

 

[jlow]

I think it is difficult to pressure data to proof or dis-proof whether there is a pressure wave bouncing back and forth – here is the reason.

What you are looking at when you see a pressure curve is the overall pressure which is read from a strain gauge probably located at the chamber. It does an excellent job of measuring overall pressure inside the chamber over time from the ignition of the powder.

However, the real question is what is the magnitude of the change in pressure from a pressure wave bouncing back and forth between the chamber and the crown that can affect bullet release? It is likely not the same as that at the chamber, and most likely much smaller in magnitude as this is from the resonance/ringing of the barrel and not absolute expansion of the chamber. My guess is even very slight expansion of the crown or flicking of the crown (which ever we believe) can cause a significant effect on group size. Remember, we are not talking about huge changes but changes that affect group size at 100 yards of one or more inches or less.

 

[CatShooter]

I think it is difficult to pressure data to proof or dis-proof whether there is a pressure wave bouncing back and forth – here is the reason.

What you are looking at when you see a pressure curve is the overall pressure which is read from a strain gauge probably located at the chamber. It does an excellent job of measuring overall pressure inside the chamber over time from the ignition of the powder.

Not so - the strain gauge reads ANY expansion of the metal - if there is an expansion from gas pressure, and an expansion wave moving through the area of the tape, it will show both on the graph.

Here is an interesting article on muzzles. One of the better shooting magazines (Rifle or P.S.) did a similar article using a bench rest rifle.

http://www.longrangehunting.com/articles/rifle-crown-1.php

 

[seymour fish]

Cat, What is the time in milliseconds on the horizontal axis of your graphs? Seymour

 

[CatShooter]

Cat, What is the time in milliseconds on the horizontal axis of your graphs? Seymour

Roughly 1.5 - 1.7 mils