[time-nuts] Why .30 cal holes can't be seen at 800 yds...
Michael Baker
mpb45 at clanbaker.org
Wed Nov 3 18:10:25 UTC 2010
Timenutters--
The question was asked-- Why can't a large aperture
high-resolution optic be used to locate bullet holes
in a target at 800 yards?
Consider this--: I often shoot at targets on the
600 yard berm at the Manatee Range (near Bradenton,
FL). Typically, by 11AM the atmospheric shimmering
mirage distortion makes even the 4" target hard to see.
By 1PM the use of any rifle scope magnification
greater than around 10X is an exercise in futility.
Often, the mirage is severe enough that even the
12" steel plates are hard to find through a 10X
scope.
.30" holes in a target...? No way.
-----------------
Other questions that were asked: To what degree of
accuracy can the 800 yard distance be measured?
I have a laser range-finder which has been verified
to be within +/- 20 inches out to 1000 yards (the
U of F college of Engineering has a series of distance
marker posts set up for some research they were doing).
What kind of accuracy is expected for measuring bullet
velocity at the shooting bench and downrange? I have
a set of Oehler Research sky-screen chronographs that
use a 10MHz crystal for clocking the counting registers.
The projectiles start out at roughly between 2750 FPS and
3100 fps and end up downrange not slower than around
1800 fps. Assume sky-screen clocking ambiguities of
only a couple of clock pulses.
As an aside, projectiles whose velocity drops to
sub-sonic at 800 yds are of no interest to me.
The transition from super-sonic to sub-sonic generally
includes conditions that create inaccuracy.
I am VERY grateful for the feedback on this topic!
A couple of innovative suggestions from list members
have given me food for thought and I am going
to pursue looking into them.
My first chore is to investigate what kind of pulse
rise-times I get from a selection of inexpensive
ultrasonic sensors when a supersonic bullet passes
within a couple of feet from them. I have a Tek
2252 scope that I can place downrange to look at the
sensors with but storing the waveform for examination
may be a problem (no one seems to have volunteered to
stand downrange monitoring the scope screen!)
The Tek 2252 has a Centronix screen-capture printer
output but it is an Epson FX format and I have no
idea if any current printers at the local Office Mart
are compatible with the Epson FX data format. Anyone
on the TimeNuts list have any thoughts on this?
The 2252 scope also has a GPIB port but I don't know
if it outputs the printer data. I have a Sparkfun
GPIB/USB dongle but that may not be of any use if
there is no printer data on the GPIB port.
Mike Baker
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