Prove? I don't think so in either case. Copper wash only proves that the conditions are right for copper wash. Expansion or the lack thereof might only be one of the conditions that could result in it.
Inaccuracy node?
- Thread starter FatOldMIHunter
- Start date
Prove? I don't think so in either case. Copper wash only proves that the conditions are right for copper wash. Expansion or the lack thereof might only be one of the conditions that could result in it.
BoydAllen
Gold $$ Contributor
Lacking any way to measure what is going on except with a chronograph, wind flags and a target, sometimes the most honest answer is, "I don't know." People have a tendency not to like saying that so they make things up and argue about them, which is of course a complete waste of time. I stick with when I do this that is what happens. It is much simpler to deal with and IMO much more honest than some unverifiable theory.
That was one of the reasons for the repeat of the group and the two nearest groups. Of course it's possible that the shooter (you) repeated the same holds on the same charge weights, but how many times would the results have to match before you would look elsewhere?
Several times. All the variables us humans have can increase group sizes more than small changes to the load does.
Raythemanroe
Bullet Whisperer
I'm kinda a ladder tester I guess:
Alex Wheeler: "When the ES says there is more vertical than the paper shows, you have possitive compensation. If you tune at 1k and find two consecutive powder charges with different velocities and those 2 groups overlap on the paper you have possitive compensation. If you are not tuning at the desired range you'll never find the spot where possitive compensation is happening. Its just before the barrel stops at its highest point. If you tune at 100 you may pick a load where the barrel is stopped, then you must rely on your es being perfect every time."
"When you have a 15-20 fps es, that says you should have 3-4" of vertical not including conditions, bc variation, gun handling exc. but you just shot a 2-3" group thats all the proof you need. See it all the time. To find the right spot, shoot at your intended distance 600 or 1000. Find a spot where a velocity increase does not make a point of impact change. There you have it. It only works at one distance."
Ray
Alex Wheeler: "When the ES says there is more vertical than the paper shows, you have possitive compensation. If you tune at 1k and find two consecutive powder charges with different velocities and those 2 groups overlap on the paper you have possitive compensation. If you are not tuning at the desired range you'll never find the spot where possitive compensation is happening. Its just before the barrel stops at its highest point. If you tune at 100 you may pick a load where the barrel is stopped, then you must rely on your es being perfect every time."
"When you have a 15-20 fps es, that says you should have 3-4" of vertical not including conditions, bc variation, gun handling exc. but you just shot a 2-3" group thats all the proof you need. See it all the time. To find the right spot, shoot at your intended distance 600 or 1000. Find a spot where a velocity increase does not make a point of impact change. There you have it. It only works at one distance."
Ray
Accuracy and scatter/inaccuracy nodes both occur approximately 3% apart and 1.5% apart from each other
mram10
Ray or Alex, why only at one distance?
dgeesaman
Gold $$ Contributor
Interesting questions. I definitely agree it's a theory, but it's one based on sound solid mechanics theory.
The resonant frequencies described neatly on varmintal's page are different from the impulse reflection called in OCW theory. So consider the two sources together.
The oversized bore barrels are an interesting comparison, but only partly comparable to an OCW scatter node. In OCW theory, the scatter node occurs when the barrel switches from expanded to contracted almost instantly.
David
Dusty Stevens
Shiner
The most likely way to find an inaccuracy node is to copy my loads
Then why does the OBT theory use a speed of sound different than other mechanical engineering site's speed of sound? I think the OBT theory was dreamed up then rate-time-distance formulas were concocted to match it.
And the OBT theory claims near instant muzzle diameter change at one frequency and Varmint All's industry grade software show it changes in a smooth sinusoidal rate at a much different frequency.
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Okay, so assume you've run enough repeats to satisfy yourself that you aren't changing the way you're holding the rifle for that one specific load. What's the next thing you would suspect?
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Rifle has loose parts fit.
That only shows up on one particular charge weight? I would not expect that.
Just as you found a scatter node I literally fell on the opposite for my hunting 308 and 130 SP Hornady's.
A max (listed...and compressed) charge of ADI 2208 (Varget) resulted in sub 1/2 MOA and ES of 6 fps.
Something that rifle had never done before with any load/projectile combo that I'd ever tried.
There's always a surprise with reloading, it might be good or bad.
I should try and improve it more as there's no doubt I could but the deer won't notice if it shoots any better.
Raythemanroe
Bullet Whisperer
Probably a Savage
Ray
Ray
jimmymac
Jim McGregor
IMO, we tend to overthink things and end up down the rabbit hole looking for answers. Theory is great, but I try to keep things simple. If I have repeatable results that are bad, I stop using that load combination. If repeatable results are positive, then it's lather, rinse, repeat and smile. I'm just as inquisitive as the next guy but only to a point. I'm not interested in getting buried in theory. YMMV
Well said. This has been observed and proved for over a century with rim and center fire rifles.
It works at one range because slower bullets have a more curved trajectory than fast ones. Use your favorite software with two velocities 30 (or 60) fps apart with a zero at one range and a maximum range further. The slower one's trajectory will be above the faster one's at closer ranges, below the faster one at longer ranges.
Compare both velocities trajectories with a 200, 500 and 800 yard zero. All with a 1000 yard maximum range.
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dgeesaman
Gold $$ Contributor
The speed of sound in steel is confirmed here: http://www.classltd.com/sound_velocity_table.html
That puts the frequency of a reflected impulse at several times faster than the resonant modes.
The sinusoidal shape of resonant is different than impulse motion.
David
That is one of the faster speeds listed across several web sites' speed of sound tables for stainless steel.
The speed of sound in solids is often measured with a rubber ruler; in my opinion.
This sounds like a job for the new Myth Busters, if they had a year and an unlimited budget for high speed cameras and strain guages.
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