Shooting 600 Yards for Score
Wednesday Club Shoots

I am starting to think about the 600 yard Wednesday Club Shoots.  I will be shooting my AR-15 and one of my shooting buddies will be shooting his new 243.  So what is the difference between them in terms of score shooting through changing conditions?  I ran a series of computer bench rest group simulations with varying conditions to see what the difference is between the Sierra 80 grain 223 Caliber MatchKing, Sierra 155 grain 30 Caliber Palma, Sierra 175 grain 30 Caliber MatchKing, Sierra 107 grain 6 mm MatchKing at 600 yards.  The velocities selected for the 223 and 30 caliber bullets are what I am getting from my AR and Silhouette rifle.  The velocities for the 6 mm to compare the 6 mm to the 233 at the same velocity and one is what David Tubbs is getting from his 6 mm X and I think typical for the 243 cartridge.

The conditions or variables changed in this simulation were muzzle velocity, horizontal wind speed, horizontal wind direction, and vertical wind speed.  In order to get understanding of each variable and in the simulation let first review a simulated target under constant conditions.  So the first of ten targets target shows all 100 shots through the same hole at 600 yards with the muzzle velocity standard deviation set to zero, horizontal wind speed variation set to zero, horizontal wind direction variation set to zero, and no vertical wind variation.  So if you had a prefect rifle and a prefect hold along with a prefect release under prefect non-changing conditions you would have a prefect one holier at 600 yards.  So this is the base line for the simulation.

(80_223target600NV.jpg)

The conditions or variable changed are what I call typical changes.  Muzzle velocity standard deviation of 12 is very typical for high power reloading.  A 15 mph wind may sound high but can you tell the difference between a 12 mph and an 18 mph wind?  I can not tell the difference in a ±3 mph wind blowing at 45 degrees.  Same for wind direction, can you notice a ±5 degree change if the wind is blowing a 45 degree angle.  Not all the wind blows in the horizontal direction, so let’s vary the vertical component just a little by only ±0.5 mph also. Next we will look at simulated targets with only one of each conditions varying and the rest held constant.  Next target shows the affect of changing the muzzle velocity only.  Muzzle velocity with a standard deviation of 12 and it’s affect with a constant 15 mph 45 degree cross wind.  The bench rest simulations were also run on a target analysis program.  Each of the one hundred shots are plotted and numbered.  The target is scored.  The bullet, velocity and score are shown on the top line of each target.  The conditions used are shown on the bottom line of each target.  So a standard deviation of 12 at 2750 fps with the 80 grain 223 Caliber MatchKing will hold the x-ring about 85% of the time.  The velocities selected in the simulation are evenly distributed within ±3 standard deviation units are not a normal bell curve distribution.  I did not know how to make the random number produce a bell curve distribution when all of the following examples were made.  Must be a way and if anyone knows, please sent me the formula.  Someone did and Silhouette Ballistics now uses a bell curve type distribution for all variables in the simulation. On the other hand, the bullet ballistic coefficients are a statistical average so the plotted affect of muzzle velocity variation may be closer to the real world than bell curved variation.

(80_223target600SD.jpg)

Now let’s look at just the horizontal wind speed.  The ±3 mph at 45 degrees would also be like a ±2 mph change at 90 degrees.  Bottom line here is how good are you at reading the wind and slight wind velocity changes?  You have to be good or you are going to drop and few points.  Nothing new here is there?

(80_223target600WS.jpg )

Wind direction only.  Question is how good you are at judging the wind direction.  Using only ±5 degrees may not have been enough.

(80_223target600WD.jpg)

The vertical wind component is something you do not hear much about.  It has to be there someplace.  So add in just a little for the rolling hills and wind eddy’s.

(80_223target600VW.jpg)

Now let’s look at everything together.  Under these varying conditions the 80 grain Sierra MatchKing score a 976 – 35X.  How does this compare to a 155 grain Sierra Palma bullet.

(80_223target600.jpg )

The 155 Palma bullets is no walk in the park to shoot and the 80 grain 223 is about equal to it at 600 yards.  What about the 175 grain Sierra 30 caliber MatchKing I use for silhouette?

(155target600.jpg )

The 175 picked up a couple of points over the 80 grain 223 and 155 Palma bullet.  How good are the 6 mm bullets in this simulation?

(175_308target600.jpg )

First let’s look at the Sierra 107 grain 6 mm MatchKing at 2750 which is the same speed has the 80 grain 223 caliber MatchKing.  The little 107 can hold its hold all right.  Now David Tubb is driving in at 2970 fps.  How much better will the extra 220 fps make?

(107_6mmxtarget600.jpg )

That extra 220 fps could mean an extra point or two and a higher x count for those who can shoot like the Tubb.  This muzzle velocity is also typical for a normal 243 cartridge using the 107 pill.

(107_6mmFxtarget600.jpg )

So bottom line to all this is.  The difference between a standard AR-15 Match Rifle using 80 grain 223 caliber MatchKings and a custom Winchester 243 caliber bolt action match rifle using 107 grain MatchKings on a typical windy day is around 24 points and 26-X for a 100 shots.  That is around 5 points and 5-X for 20 shots.  So if Cope wants a Medler Buck, he should spot me 5 points and 5-X’s at the Wednesday night 600 yard shoots.

The above bench rest groups and targets were computed using:
Silhouette Ballistics – Bullet Trajectory Software

Related Article:
Shooting Palma Bullets - Sierra 155 Grain MatchKings

Sierra Palma at 2950 fps.

(155target600yd2950.jpg)

90 JLK at 2750 fps, used .560 for the BC.

(90_223target600.jpg)

6PPC 68 gr. Hottenstein at 3350 fps, .290 BC

(68_6ppctarget600.jpg)

Larry Medler
anyrange@comcast.net

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