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
Requested Targets Added.
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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Released July 8,
2003
Revised July 17, 2009
