Shooting Exercise I


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echo3mike
May 15, 2003, 04:46 PM
This will be the first in (hopefully) a series of exercises designed to give members a chance to work out firing solutions (sight adjustments) using real world data. While there are many members here who can get to ranges longer than 100yds, most members have limited access to ranges longer than this or don't have the background or opportunity to work with the more intricate aspects of marksmanship. These exercises will give members here an opportunity to work out some of the problems associated with rifle marksmanship.

The calibers selected for these exercises are fairly common. Most members have some familiarity with them. Regardless of the level of familiarity, I'll try to provide enough information to allow those members who don't have the background ample opportunity to participate.

The process is simple. Use the data given in the post and ANY OTHER SOURCES YOU HAVE AVAILABLE to acquire the firing solution. There are a number of ballistic freeware websites available (including JBM's Ballistics Page (http://www.eskimo.com/~jbm/index.html) , and Point Blank Ballistics Program (http://www.huntingnut.com/pointblank.html) to name two) that can be used to get the basic trajectories and some of the more advanced data. Other sources include military manuals, marksmanship training books, other BBs' and such. As a courtesy, please cite your references and / or explain your process so that others can learn as well. All the information you'll need to solve the problem will be in the post. I'll post the answers after the post has died, or I'll PM the solutions if needed.

SHOOTING EXERCISE I

So you finally get out for some trigger time to your favorite hunk of land to play with your Winchester 70 in 30.06. It's a weatherman's favorite day, pure Standard Atmospheric Conditions (SAC): 59.6 degrees F, Barometric Pressure of 29.92 in Hg, 0% humidity, and your range is located at 0ft ASL. You got your 100yd zero the previous weekend, and it's still on the rifle. It looks like your psuedo-M2 Ball handloads ( Sierra .308 cal 150gr FMJBT w/ BC at 0.266, MV of 2740fps) are working well.

Unfortunately there's only one really safe direction to fire where you're shooting...and it looks like someone has left a 55 gallon drum right out there...and kind of far away. Since it's been raining for a few days, the drum is probably full of water...too heavy to move safely. A few holes in that drum would make it easier to move, wouldn't they? You set your gear up and pull out your laser range finder to get the distance...500yds exactly.

The wind seems to be pushing your wind flag out to about a 40 degree angle to the pole, and it's coming from 1:30. You also note some dust and loose paper being raised by the wind.

Exercise:
- with the given information and any source available to you, what windage and elevation adjustments are needed to engage this target from your 100 yd zero? (Note: use MOA instead of "clicks").

S.

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Steve Smith
May 15, 2003, 06:32 PM
Lots of lookers, no takers, man. I don't wanna give it away.

ACP230
May 15, 2003, 07:58 PM
I wouldn't change my zero. I'd just hold on the windward edge of the drum about eight inches down from the top.

hps1
May 15, 2003, 08:00 PM
echo3mike:
How many holes you want and how dry do you want the barrel?;)

The flag may be the hardest part for most folks to convert to wind velocity.

Great exercise, hope you get lots of participation.

Regards,
hps

Fly320s
May 15, 2003, 08:44 PM
I have no idea about windage and elevation, but standard atmospheric pressure at sea level is 29.92 in. hg.

If I had to try, I'd use my AR and all the mags I need to get the job done.

Brian Williams
May 15, 2003, 09:07 PM
I would put in about 45 clicks up about 11.25 in at 100 and 10 clicks R and hold to the top edge of the barrel

Barrel about 48" high
7mm-08 drops 58" in 500 yds
150 gr ballistic tips pushing about 2700fps
should put a hole about 1" to 4" up from the bottom

Wind is a little gusty so a few shots might spread the group and drain it quicker.

This is from memory.
Mine is a mod 70 but I prefer the Short action Classic compact in 7mm-08 with a 3x9 leupold compact scope

Quack
May 15, 2003, 09:07 PM
what's the barrel length? :)
got the MOA, now just gotta figure out the flag

hps1
May 15, 2003, 09:21 PM
55 gal drum is 36" tall.

Quack
May 15, 2003, 10:42 PM
um...on the Winchester 70 ?

DJJ
May 15, 2003, 10:44 PM
Assumptions:

1. 55 gallon drum is 24" diameter and 42" (3'-6") tall.

2. It hasn't occurred to you that since you plan to move the barrel anyway, you could walk out there and shoot it with a pistol. :neener:

3. Scope is 1.5" above the bore.

Oehler's "Ballistic Explorer" says that with those settings, trajectory at 500 yards is about –79.5". The Speer manual (no Sierra manual) is in general agreement (-80" for 2700 fps and BC = .27).

www.snipersparadise.com has a tip for reading a wind flag: divide the angle between the flag and the pole by 4 to get wind speed: 40 deg. / 4 = 10 mph. Ballistic Explorer gives a wind drift of around 31" to the left with the wind at 1:30. The Hornady manual gives a drift of 22.4" for a 7mph crosswind component (10mph at 45 deg) and BC = .27.

I'm more of a practical rather than precision shooter, so I wouldn't mess with the scope settings at all. I'd hold 1 "barrel height" above the top of the barrel, (or 2 barrel heights, or 84" above the ground), or a little higher, which should get the bullet in the first foot above the ground. For windage, I'd hold 1 barrel diameter to the right of barrel centerline.

In MOA, 15 MOA up and 4 to 6 MOA right (depending on which value for wind drift you buy), as near as I can figure (geometry).

hps1
May 15, 2003, 11:14 PM
Agree w/DJJ.

Wind is 10mph @ 45* angle = 30" drift so need 6moa right windage. (Wind info from Champion Rifle Score book, same formula as used by DJJ). Might have slightly more wind than indicated by flag as M/Sgt James Owens' book "Reading the Wind" shows blowing dust/paper @ 13-18 mph.

Need 16 moa elevation from 100 yd. zero due to 80" drop according to: http://www.norma.cc/htm_files/javapagee.htm

Scorebook wind values show less windage (3moa), but was calculated on the 173 gr. M 72 (boattail) bullet @ 2640 which would drift less than the flat base 150 M2. Norma program shows the 30" drift for the 150 which is probably closer to correct.

Regards,
hps

Andrew Wyatt
May 15, 2003, 11:22 PM
I don't fiddle with my scope adjustments unless i'm zeroing the gun.

since i'm st the range, i'd have my number4 mk1 in .303 with me, as well.


i;d set the rear sight to 500 yards, and hold dead on. :neener:

echo3mike
May 16, 2003, 10:28 AM
Most of the folks who did the math came pretty close to the numbers I got...I think I'll go ahead and post my findings so this doesn't become a whizzing match over who has the best trajectory calculation program.

ELE: ~18.5 MOA up from 100yd zero
-JBM has 90" drop / 17.2MOA
-Point Blank has 104" drop / 19.9MOA

WIND: ~5MOA Right
-JBM has 10.3MOA / 54" FULL VALUE
-Point Blank has 9.75MOA / 51" FULL VALUE
-> since several sources have differing percentages of full value windage, I tried to make it as close to 50% as I could by using 1:30 as the direction.

If I'm doing the math right, a center mass hit at 21" above the base of the drum gives about +/- 4MOA ele and +/-2.25MOA windage to still score a hit on the drum. Most of the programs came within these parameters. I don't think they fall outside the variations associated with rifle / ammo combination differences...which means ya' still gotta go out and shoot the thing to confirm your come ups. As for the hold-overs, I don't think they would have fared as well. If you look at the total drop and the size of the drum vs. the hold positions given, I'm thinking that most would have been misses on the first shot. Hold offs can work well and they have their place, but out past zero distance + 400yds or so sight manipulation is almost imperative for first round hits.

DJJ took this exactly where I was hoping to go...read the data, find the appropriate method to extrapolate the firing solution, raise it up and see who salutes. Strong Work! This exercise focused primarily on using observation and mathmatical formulas to acquire the windage from environmental factors. What I'm really hoping to do is have folks go through the process of obtaining a firing solution verses getting a "correct" answer which is obviously going to be different in regards to what program is being used.

Which reminds me...there is homework posted (Shooting Exercise I-A and I-B). Have fun!

S.

Sources:
- Reading the wind and coaching techniques (http://jarheadtop.com/books), byJim Owens;
-Michealis, D. The Complete .50 Caliber Sniper Course; Hard Target Interdiction (http://www.amazon.com/exec/obidos/tg/detail/-/1581600682/ref=pd_rhf_p_1/104-8972754-0434341v=glance&s=books) Paladin Press, Boulder, CO. 2000
-JBM's Ballistics Page (http://www.eskimo.com/~jbm/index.html)
-Point Blank Freeware (http://www.huntingnut.com/pointblank.html)
-FMFM 1-3B, U.S.M.C. Scout / Sniper Manual (https://www.doctrine.usmc.mil/htm/doc5.htm)

Steve Smith
May 16, 2003, 10:33 AM
I like the way that DJJ attacked the problem.

"divide the angle between the flag and the pole by 4 to get wind speed: 40 deg. / 4 = 10 mph"....that is a good quick way to get it and it works. Obviously it depends on flag size and material, but if the range is using an NRA approved flag, its good info.

Those of you being lazy with the holdovers, get out those calculators!

Stickjockey
May 17, 2003, 03:53 AM
Oooohh boy...

It appears that I've got a lot more to learn than I thought...

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