From: "E.J. Totty", [EMAIL PROTECTED]
> ---snip---
>What I did find was a marked difference in elevation when I checked zero in
>Africa. Rounds were 7" higher at 200m than at home.
>I put this down to the fact that it's almost sea level where I zeroed, and
>when in Africa we were at 4,000+ feet asl. Add to this the temperature being
>42 in the shade and there is bound to be an increase in pressure. No signs
>of excess pressure on the cases, but as the case is almost filled to
>capacity with powder, it would be interesting to know what the increase is.
>If anyone has any experience of high altitude and high temperature
>performance, I would be interested in knowing. (OK, difference could well be
>also due to airline baggage handling techniques).
>
>IG
Steve, & IG,
Rather interesting.
The increased accuracy (decreased drop) is accounted for
by the thinner air at 4k feet. The temperature would also make the
air thinner, giving less resistance to travel.
Would you happen to remember what the relative humidity
was (i.e., was it hot and dry, or more moist)? Moisture tends to affect
accuracy quite a bit.
As an anecdote, an acquaintance of mine who shoots competition
target recalled that at one particular shoot -- which began in the cool air of
the morning (and when everybody had sighted-in their shooting instrument)
-- that as the temperature was rising that the bullets would also tend to drift
towards the spin axis of the bullet. That is, if your rifling is
clockwise (viewed
from breech), that the bullet would tend towards the northeast of bull's eye of
the target as the temp. increased with the rising sun.
This was accounted for by the spin of the bullet riding the thermals
that were starting at ground level as the sun heated the area between the
shooter and the targets (over a mile away).
Apparently, if you really want to be super accurate in your
shooting skills, it seemingly pays to carefully note the atmospheric
conditions that exist when you sight-in, and take into consideration whatever
other conditions presently exist and compensate appropriately.
--
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