So you're saying you've run cables to your acoustic screens out to almost a quarter mile? WOW. That's gotta be a 'ell of a spool of wire.
Would you mind telling us what screens you used, who is "we", and why you didn't document any of this if you went to that much work?
"We" is myself and a friend who'll remain nameless, the screens we used aren't screens, they're a pvc framework in which are mounted acoustic pickups. We fired through the acoustic target. My plan was(is) to set up my range so that every 300-450yd group was plotted and recorded at 100yds. My range
is now wired to 100yds with CAT5, RG6 and 110VAC so's we can run the acoustic target at 100yds and print on paper at 350-450yds. The system was an Oehler43 which is no longer here. I'm now in the position of having the setup but no longer being able to get an Oehler43. see here
http://www.oehler-research.com/model43.html So my situation is that we cobbled the 43 together by dragging wire above ground, got it working before I had my range wired and fired some groups thru it. It's awesome. I plowed in the cable and my buddy moved and took the Oehler43 with him. No big deal at the time, I was just going to buy my own.....and then Oehler discontinued production. I've since had the chance to buy a used one but hadn't the funds at the time. Now I'm again looking for a good Oehler43.
Since I didn't have the 43, but I still wanted to test some stuff I then ran some poles up and suspended paper targets to shoot through.....and measured THE SAME GROUPS at both distances. The reason nothing's "documented" is because collating the information is a lot of work. I've got a stack of notes and notebooks and folders a foot tall.
Don't really know why I'm "explaining myself" since until someone else takes the time/money to actually DO THIS STUFF I can tell from listening that everyone else here is just speculating.
Meanwhile there are two other people on this board who've actually done this stuff. And their results agree with mine. And ARE somewhat documented. (They wrote articles on their experiences)
But they're not participating in this thread.
Interestingly enough, in a conversations with Harold Vaughn I brought up this idea of groups converging with distance. Another one I brought up with him was the idea that "a dirty bore will increase friction and raise pressure and therefore velocity" (another Urban Myth perpetuated by shooters) and in both cases I wish I'd "documented" his replies
Harold was one of those truly rare specimens in the world of engineering who tried to understand the "why."
And generally succeeded.
BTW, his answer to the idea of "trajectory converging with distance" was remarkable in it's simplicity......... "You postulate to me a mechanism, a force acting "inward" on different bullets and we'll talk about whether or not it's possible!" And of course I couldn't.
Because there isn't one.
Some have contended that the coning motion itself produces and "inward" component. But
IF YOU UNDERSTAND that bullets are SUCKED off course by base drag an idea ref'd earlier in this thread,
then all the liddle "coning diagrams" can possibly "prove" or show to support the contention of convergence is that base drag is _possibly_ increased by the _possibly_ increased presented frontal area and that this increase in drag _could_ be directed to the side of the bullet behind the slewing tip. This _could_ produce an inward force, the result would be that the bullets would lose a little velocity, translating it into "steering to center." Which in Harold's opinion was so small a mechanism that it was impossibly down in the dirt. Numerically there's no difference in drag between a coning bullet and an "asleep" bullet. In other words, coning bullets exhibit the same BC as "sleeping" ones. Therefore, the concept of using drag as a mechanism for "steering bullets to center" doesn't compute. Math don't lie. And in Vaughn's models (generally taken from McCoy's work and others at Aberdeen) the math does work. All forces balance and are accounted for. There is no "Dark Matter" conundrum, no unexplained loss.
And then we come to the real elephant in the ointment........ let's say individual bullets DO settle down and hew more closely to "the center of their flightpath"...... let's accept that maybe an individual bullet DOES somehow steer to center......
So What???
"Groups" are formed by disparate bullets following disparate flightpaths....and here I'll again illustrate The Wisdom of The Wilbur.
Wilbur postulated a model a couple years ago where IT WOULD BE POSSIBLE for a single group to exhibit this characteristic of convergence. IF a group were to be fired and plotted wherein every individual bullet went through the 100yd target on the OUTSIDE of it's individual "orbit" and each individual occurrence occurred at a different point around the center of the group (like a ring) and then settled down onto it's individual flightpath then THAT GROUP could in effect "show convergence." The 100yd group would be a circle which would measure larger than the eventual group because the individual "centers" would be inside the individual "outside orbits." See Wilbur, i don't forget, much.
Problem is, it would be pure-dee LUCK....... for every time this did happen it would NOT happen many other times.... the bullets would pass through the first target NOT on the outside of their orbits. So the net effect would not be "a rifle which fired tighter groups with distance" but simply an occasional anomolous group.
And now on a totally different subject, it IS not only possible but
predictable that bullets can converge on the vertical plane..... that a rifle tuned to the water table at 600yds may well show a tall stack at 300yds. This is repeatable, AND one of the things I intend to map with my Oehler43 setup if I can ever find one.
Anyone out there got an Oehler 43 Ballistics Lab they'd part with???
just askin'
I've GOT the coil of wire sticking out of the ground. Just mowed around it the other day...
LOL
al
