Antelope
Anticipation
Prior
to an upcoming pronghorn hunt, the 10ML-II was confirmed at both
102 yards and at 220 yards. The specific load selected was 57.1
grains N120 pushing a .458 Barnes Original 300 grain Spitzer Soft-point,
housed in the current formulation orange .50 / .458 MMP sabot. A
Winchester 209 primer, a .033 RW ventliner completes the array,
topped off with a Bushnell Elite 3200 4 -12 x 40mm scope with a
ballistic plex reticle. Muzzle velocity is approx. 2250 fps.
The
"Plainfield, IL" BC at this velocity and at 220 yard range
is an actual .260. The specifics are illustrated in the illustration,
as most illustrations aspire to do:
Late last evening, preliminary
sight-in was confirmed, but it was a bit too windy to do any reliable
long range work. This morning, by hopping out of the sack at 3:30
AM, we were able to beat the wind-- and I picked up my Dad on the
way down to field. With dead calm as the sun rose, it was wasy to
confirm this load with three consecutive sub 1/2 MOA groups, 3 inchs
directly over the bull @ 102 yards. Then, time to set up for some
220 yard work.
With
still no wind to deal with, the first two shots at 220 yards fell
about 1 1/8 in.CTC from each other, right at 4" low.
Ballistics
@ 220 yards, 500 ft. above sea level, are about -3.97 in., 1643
fps, 1797 fpe, ETA of .344 seconds.
At 5000
feet above sea level, a bit more representative of the hunt:
-3.26
in., 1727 fps, 1986 fpe, ETA .335 seconds @ 220 yards.
My windmeter
picked up light, gusty winds from the North, from 4.2 to 6.4 mph--
a direct cross. The next three shots resulted in a 1-3/4 in. CTC
three shot 220 yard group, blown slightly to the left.
Satisfied
that those shots would have been five dead pronghorn, and with the
first cross-hatch of the ballistic reticle meaning 3 inches @ 100
yards, it should be straight through the body out to 220 yards,
line #1 of the ballistic reticle good-to-go to 275 yards. It likely
will shoot a bit flatter than that due to the area 44 elevation
outside of Laramie, WY, but that will naturally be confirmed on
location prior to hitting the field.
The
second line of the reticle keeps things in the vitals out to 300
yards, with 1560 fps, 1621 fpe terminal, .482 sec. ETA. I'm advised
by Barnes that the Barnes Original Spitzer Soft Point needs more
velocity for reliable expansion than their MZ-Expanders; in this
case about 1400 fps. I believe this statement is from shooting into
fluid only, void of any bones. Out to 300 yards, we are still well
exceeding that terminal velocity and still whacking our animal with
better than 3/4 of one ton of striking force.
I've
written enough about ballistic coefficients, perhaps too much. What
most people need to know is that they are all wrong. Any
single BC number has to be wrong, as the operating drag coefficient
is constantly changing in concert with velocity. The observed 220
yard average .26 BC cited and used here increases as velocity decreases;
the operating average BC is far higher from 200 - 300 yards than
from 0-100 yards. Due to this fact, the actual drop from 200 - 300
yards will be even less than calculated with the .26 BC.
As
it stands, this is still the flattest flying muzzleloading projectile
I've tested that can be shot with accuracy-- far flatter shooting
than any 300 grain Precision Rifle bullet, and flatter shooting
than the Hornady 300 gr. SST. It would be misleading to suggest
that this of great importance inside 100 yards; it really isn't.
As the range increases past 200 yards, it is of course critically
important to vertical drop, and of even more importance in resistance
to wind deflection.
©
September 15, 2005 by Randy Wakeman
