Project Appleseed

Hey Folks,

I am fairly unfamiliar with optics and could use your opinions and advice.

Before I get too involved with my questions it would make sense to explain the event so that you could give me better feedback. The event consists of 5 stages. The shooter will start at the target line and engage targets from 8 to 10 inches in diameter at unknown ranges between 100 and 600 yards.  The shooter will have 12 targets and 2:00 minutes maximum to engage all targets.  This means that I will need to be able to rapidly adjust for the new range without spending half an hour counting 4023802382 clicks. 

Problems:

How to adjust for range rapidly?
How to estimate range rapidly?
^This is not as vital considering my field shooting experience should get me close but I would love a way to get a more accurate range. (mils? )


The picture below is of the turrets. 

Possibly Useful Information:
If it is any correlation the scope is a 4.5-14x50
1 click = .5 cm at 100 yards.
The rifle is chambered in 6.5 Grendel


Thanks in advance,

TK

BTT -Tomorrow is my last day to get dope before the competition.

http://www.mil-dot.com/Mil_Dot_Reticle.htm#MilDotIntroduction


Read here. Then try the classroom version. Use a ballistic calculator to get your come-ups...should be close.

Best I can do.

I'll take a stab at it. 

I don't have a 6.5 Grendel myself, but to some extent bullets all do the same thing.  Looks like you have an AR-patterned rifle.  You didn't specify bullet weight or barrel length, which will have some effect on the trajectory; also the height of your sights above the bore will affect how you perceive the trajectory.  So there are likely to be some minor differences between how your rifle shoots and a "rough guess."  But we can work out the rough guess.

There's a good write-up on Mil-Dot scopes here:  http://appleseedinfo.org/smf/index.php?topic=16701.0 (http://appleseedinfo.org/smf/index.php?topic=16701.0) (may not be readable by everyone)  Basically the "mil-dot" means your scope measures in "mils" or 1/1000ths of a radian.  That means the distance between any two dots on the scope is equal to one one-thousandth of the distance to the target.  You can use this both for range estimation and to adjust your fire.

Let's do range estimation first.  You said your targets are all 8 to 10 inches in diameter.  Let's say they're all 10 inches to make our life simpler.  At 100 yards ( = 3,600 inches), that target will appear about 3 "mils" wide, because 10 inches / 3600 inches =  about 3 / 1000.    Similarly, at 200 yards they will be about 1.5 "mils," at 300 yards they will be about 1 "mil," and so on.

So to estimate range, hold the scope on your target.  If they're all 10 inches across, then your 600 yard target will span about half the distance between dots.  300 yard will about span between one dot.  And so on.

Now for the range adjustment.  Let's assume your rifle starts with a 200 yard battlesight zero.  We need to know the trajectory of your round at different distance.  I found a table here, in the third post:  http://www.65grendel.com/forum/showthread.php?t=6866 (http://www.65grendel.com/forum/showthread.php?t=6866)  I don't know how accurate this is, or how well it fits your rifle, but it's the best I can do for now.

This table presents estimated bullet drop relative to a 200 yard battlesight zero.  At 200 yards, you would make no adjustment ("-0.0").  Let's start looking at 100 yards.  From the table, the adjustment at 100 yards is 2.1 inches, so you would adjust your scope 2.1 inches down at 100 yards.  In mils, this is 2.1 inches / 3600 inches = 0.6 / 1000 = 0.6 mils. 

Your scope adjusts in 0.5 cm / 100 yards = 1/5 inch / 3600 inch = 1/18th of a mil -- it's probably 1/16th of a mil per click, so I'll use that instead.  So to get 0.6 mils, you would adjust by 10 clicks.

SO:  Using the "Inches" from the other table I linked --

Assume 200 meter battlesight zero
1 mil = 3.6 inches per 100 yards
1 click = 1/16 mil = 0.0625 mil


Couple more things to watch:

I'm also assuming the reticle zooms with the scope power.  Otherwise... the distance estimation will only work when set to the correct power.  Watch out for that.

Make sure you have your battlesight zero marked so you can go back to it QUICKLY and REPEATABLY.

Just so you know, a 10" target at 600 yards will be challenging!  Best of luck to you.

Thank you both for thanking your own time to find the information and explain it to me.  It is appreciated more than you might think. The bullet weight is 123 grains and the barrel length is 28.  It won't be easy but it isn't any funny if you hit every one! A fellow instructor and I will be competing the weekend after next, we will keep you posted.

Thanks again,

TK

The table I used assumed 123 grain bullet, but a 16" barrel.  For a 28" barrel (!!) the velocity will be higher, and the drop less.  Don't know how much.  I'd probably start by reducing those adjustments by a quarter and see what happens (e.g. 13 clicks ==> 10 clicks, 28 clicks ==> 21 clicks, etc.).  That's just a wild guess.

Nice thing about a mil-dot scope is, if you can see where the bullet strikes, you can use that to calibrate corrections on successive shots.  1 mil = 16 clicks, regardless of distance, for your scope.   O0

Most of tomorrow will be involved in just getting familiarized with the system and a little bit of trial and error but heck any information that will speed up the process is much appreciated.  Thanks again.

TK

hmm, somehow your photo is reversed.  (does that mean your bullets are loaded back-to-front?)
you have to establish reference points: a BSZ, at x range, which corresponds to 'y' on your elevation turret.
This gets written on your stock, and you can always get back to a known point; know where home is and you can always recover it. 

Break the range up into 20 yard pieces from 100, 120, ... 580, 600, 620, 640 yds (go past 600; don't trust them to place targets at exactly, but not past, 600).  Each range on your card needs a calc'd elevation or else real world elevation data. 

You'll get more drop farther out, and 20 yds ranging resolution should keep you on the plate.   
At each range, you need to have a pre-calculated elevation drum value, and number of clicks.  This gets written on a reference card and taped to your rifle someplace you can see it nearby. 
At the test range, shoot groups at EXACT distances throughout the 100 to 600+ range to establish data.  Calcs are the next best thing to data. 

'Shoot' the course at home on scaled targets- practice ranging 0.8 and a 1-inch diameter targets at 10 to 60 yds, if yard space/scope design permit.  A ranging error of one click (since one click at 100 yds gives 1/2cm) on your scope moves POI three cm at 600 yds.  you can only afford to misjudge the range by an error of + or - 2 or 3 clicks from plate center before your (let's assume) 1 MOA rifle falls off paper.     

Once you range a target, get real good at dialing in the range or (perhaps better) utilizing the verticle mil reticle to do it for you.    Might be a wise strategy to only plan to elevate the drum for certain key ranges, and use the vertical marks to complete the work.  Whatever you do, write it up on a card, post card where you can see it.  Would be good to post card in a position-maintenance friendly place. 

You'll have to take wind into account to make these long shots.  Research how to dope wind, including the necessary corrections in mils, or better yet, use the horizontal reticle and don't touch the windage dial.  Typically, this consists of assigning a speed to the wind, and a direction to the wind relative to the bullet flight path. 

Twelve seconds per shot; that's two or three breaths and a lot of mental math which must produce one correct BANG.  You need a fast method of ranging, elevation adjustment, wind doping.  Practice before the actual event.

Research your scope and how it works; there may be cleaner, faster solutions than the ideas mentioned here.  You might think of your scope adjustments as 1/5 MOA/click in a pinch.  Good luck.   

Dude, that Mark 4 is incorrectly mounted.  You have it canted 90 degrees counter clockwise to the way it should be mounted.  Your elevation dial is where the parallax adjustment should be and your windage is where the elevation should be.

Are you sure 1 click = .5cm at 100 yds?  Odd to have cm combined with YARDS and a 1/2 cm is pretty damn small. Most MIL/MIL scopes have .1 mil dials which would be 1cm at 100meters or 10cm at 1000 meters per click.

Start out by remounting your scope.  Then chronograph your ammo and figure out what it'll do with any basic ballistic calculator.  Then TRUTH the ballistic calculator data by going out and shooting at those actual ranges.

As for a miliradian scope, it'll be great so long as you actually have mil-based knobs matching your mil-dot reticle.  As for me, I'm a MOA guy so I use the MOA/MOA setups offered by Nightforce.  Maybe Leupold will offer those one day.

-David
Edgewood, NM

I didnt think they made MK4s with mil adjustments?  Is it possible that your scope has a mil reticle with MOA adjustments?

Thanks for all of the input guys. I ended up zeroing the rifle at 200 yards and then indexing the elevation turret back to zero.  From there I zeroed ever hundred yards and made a range card so that I knew lets say that if I needed to hit a target at 280 yards I needed to put my scope on the 7 hash mark.  It worked great for the event and I couldn't have been more pleased. 

The scope is mounted correctly its just that I used a Webcam to take the photo so it reversed everything that might be the source of the confusion. I assure you it is mounted correctly. 

Thanks again guys and feel free to Pm me any questions,

TK