Brown Dog, I think you're using 1.047197536428... inch at 100 yards as one minute of angle. That's trigonometry; the sine of one trig MOA (0.00029088820...) multiplied by 100 yards (3600 inches). I divided your 800-yard 76.9cm come up from 100 yards by your 28.9 MOA and got 2.6609, then divided that by 1.0472 and got 2.54...cm. That more or less got me thinking.
The shooting industry in the USA uses exactly 1 inch at 100 yards as a "shooting" minute of angle. That's based on the original sight radius of 30 inches on early target rifles with their rear (or back) sight moving .025-inch per revolution (their lead screws having 40 threads per inch) for three MOA per turn or .008333-inch (1/3rd turn) per minute of angle. The shooting MOA is 1/3600th of the distance; 30 inches divided by 3600 is .008333 inch.
It's also based on external adjustments on target scopes with the mounts spaced the standard 7.2 inches apart and each four 1/4th MOA clicks moving the rear adjustment .002-inch; .0005-inch per click. 7.2 inches divided by 3600 is .002-inch. Modern scopes are marked and specified for 1/4th inch per click at 100 yards although their manufacturing methods may have it a tiny bit off.
Most centerfire competition targets in the USA have scoring rings spaced on this shooting MOA standard. I used 1 inch equals 1 MOA at 100 yards for my data. That's probalby why our SWAGging and SWAPping data are different.
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Here's another variable....scope adjustment accuracy. Ever calibrate a scope's adjustments to see how far each click really changed point of impact? I've done this by putting a yardstick out at 50 yards, then benching the scope and moving the adjustments over 20 to 30 inches on the yardstick. A small percentage error is common. Evidence that if one makes a 30 MOA come up, the line of sight may move anywhere between 28 and 32 MOA depending on the scope make and model. Every internally adjusted scope I've checked ain't exactly dead-on; they all are a bit off. But each one is pretty repeatable for each click/MOA moving the same amount.
This happens because of the mechanical design of the scope. The clicks per turn for the thread count of the adjustment isn't exact for the erector tube's movement about the objective lens' primary image for perfect fractional MOA changes. But most scopes are within a few percent of being exact.
Once you know your scope's exact change per click/MOA, then you can convert the come ups from tables such as these to exactly what your scope needs to do
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Now that is probably the first post you've made that I agree with 100%. Very well said. [img]/ubbthreads/images/graemlins/wink.gif[/img]
It looks like a great bit of information was lent to IdahoWoodsBummer. That seems like a good idea, but is it?
First you wrote: "I am in a remote part of the sandbox right now and need some data badly. I cannot go into very many details for OPSEC and PERSEC reasons. I am doing a contracting job."
Who has contracted you... knowing that you and your guys have only the marginal technical skill and or proper equipment to execute?
Is that OPSEC information as well?
Second point you wrote: "Here is the scoop. My coworkers are not able to get onto a range longer than 25 meters and I do not have my Sierra ballistics program with me. resupply is not an immediate option."
A remote spot "in the sand box" with only 25 meters, or 100 meters for a target range? Hmmmm?
IdahoWoodsBummer, I don't know you, so please don't start a flame war. It seems you are too busy too do so anyway.
Having spent 21 months in Iraq, I can say with full conviction that marginally qualified, minimally equipped "contractors" are not a good thing there. Both for our currently deployed U.S. Service members, and the poor civilians there as well.
I do agree on your final point: "This is a bit of an off the wall request but I figure who to best get the data from than a bunch of LR nuts."
Sorry guys, people die "in the sand box" due to "contract" cowboys all too often. Just keeping it real.
Correct on the 1.047 stuff [img]/ubbthreads/images/graemlins/smile.gif[/img]
I agree with your sentiments, my antennae had a mild twitch too; hence my comments in my first post on this, which included:
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.....talking of 'in the parish'and relating it to your use of 'accurate, exact and Critical' ...(and, based on my very limited experience of working 'around' civilian contractors in Iraq)...might be worth pointing out that dependant on your situation in terms of your legal status, the ROE under which you are operating and the requirements of the situation/incident itself, you might want/need to consider the legal ramifications if you 'botch' an engagement (ie kill a friendly or an innocent) using a rifle that has only ever been zeroed at 25m and then set using (what has been kindly described above as) 'SWAP' data.
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....perhaps I was too polite? [img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img]
....You've expressed the concern far more clearly; there is a definite feel of "all the gear; no idea" to the original request.
......I don't know this fellow either and hope that's not the case.
...on balance (and, hence my reason for posting) I don't think the info I've given so far will be any more damaging than if
they just 'had at'.....which if this is a case of ATGNI would happen anyway [img]/ubbthreads/images/graemlins/frown.gif[/img]
.....the data requested should not be difficult to obtain in-theatre -if they were meant to have it;
Since they have the weapons; my hope is that giving the idea of creating short range practice targets and highlighting 'legalities' might make them safer -in every sense.
That kind of technical info that you have refered to in your previous posts is exactly why I figured to ask this site for assistance rather than the internet sniper sites.
If I had known prior to deployment I could have put data books and all my other dope on a thumb drive.
Live and learn.
In response to the individual from alaska:
You have no clue what we are doing or where we are or the qualifications of our DDM's. If you did you would feel very stupid right now. I suggest you keep your "marginally trained" and other "questionable" comments to yourself. Your anti contractor opinion was not solicited nor is it welcomed.
I am simply trying to give our guys a leg up in an unusual situation.
I emailed you. Let me know if it made it to you. Sometimes they go through and sometimes they do not. I was planning on shooting the state sniper championship again this year but is does not look like I will be back in time. Go easy on the prize table again OK [img]/ubbthreads/images/graemlins/wink.gif[/img]
On the next rotation you can bet a lot of my personal gear is coming with me.
Hope everyone is enjoying a great start to another rockchuck and prairie dog season.
It has not shown up at this date and time. I'll be watching. To all, I have known the bummer for years he is a experienced and more importantly successful long range marksman. Given that he comes from a law enforcement background similar to mine I suspect that OPSEC and PERSEC mean just that and are no one elses business. Lets try to provide assisting information as requested.
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In response to the individual from alaska: You have no clue what we are doing or where we are or the qualifications of our DDM's. If you did you would feel very stupid right now. I suggest you keep your "marginally trained" and other "questionable" comments to yourself. Your anti contractor opinion was not solicited nor is it welcomed. I am simply trying to give our guys a leg up in an unusual situation."
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I did not intend to insult you or your DDM "Designated Defensive Marksmen".
A DDM worth his salt, should not require this technical assistance, IMHO.
Keep your head down guy, no amount of "contract" money is worth your demise.
FYI, if you have enough time on your hands at the U.S. Military Staffed FOB currently protecting you to respond so quickly in attacking me, then this is information easily found on the web.