Shooting in a Downpour
Thought this information
might interest some of you.
Had another opportunity to
shoot in the rain last week, and as my wife reminds me, I'm not made of sugar
so I won't melt, which is good enough reason to pursue my hobby further.
Quite a few folks have never
shot it the rain and wonder what it does to bullet flight. Theoretically all those little droplets
hitting the bullet must knock it off balance rendering it impossible to hit
what you're aiming at.
Not so.
When we fire that speedy
little pointy thing from our modern rifle it's going supersonic and creates a
bow wave in front of the bullet.
Essentially the projectile operates in its own atmosphere surrounded by
a pocket of air which parts those droplets keeping the bullet on a straight
path to the target. The effect on
accuracy is limited for the most part by shooter ability to see the target in
the rain.
There are other things
happening though
..
When a bullet is fired from a
rifle, a partial vacuum is created as the bullet and expanding gasses exit the
muzzle. As this vacuum of sorts
equalizes, air, and in this case, water, is introduced into the barrel of our
rifle. So far the 1st shot went where it
was aimed.
2nd shot.
Now our shooter is back on
target ready for shot two. Things are
going to be different this time. The
rifle barrel usually full of a gas called commonly referred to as air now has
another element inside. Water.
Air as we all know is a compressible substance. Water does not compress and here in lies a
problem.
We can compress the column of
air in the barrel ahead of the bullet but that water isn't going to get out of
the way. This obstruction is going to
raise pressure in the cartridge case and chamber, possibly to unsafe
levels. When the rifle is fired,
pressure rises quickly, but the bullet may not speed up in an equal amount to
the pressure increase, due to the extra work it is doing trying to move all
that water. Because of this increase in
pressure, and the resultant barrel harmonics it causes, our bullet does not go
all that close to where we wanted it do go in the first place.
As an example, at 600 yards,
shot two is 8 inches from shot one, with the same point of aim. That assumes our shooter is pretty good on a
normal day.
With the current trend toward
long range hunting that 8 inches is a wounded animal that has to be shot
again. In the rain it's not good to
assume that subsequent shots would be all that accurate not from the rain
interfering with bullet flight but from the ancillary things caused by the
water vapor. Result is an escaped animal
or one that has to be tracked, and shot yet again. Anyone care for some hamburger?
Another factor is we're
shooting in a rain, so when the shooter cycles the action, the cartridge to be
loaded gets wet. This is not good A fired case expands rapidly and grips the
chamber walls, helping to hold it in place until pressure reduces to a safe
level. Over simplified somewhat but you get the idea.
Now we've reduced that
ability by lubricating the case, causing the cartridge head and the bolt lugs
to endure much, much more pressure than normal.
This is a dangerous situation. In
a weak rifle the results could be unpleasant indeed.
[A side note about action strength and testing.
In the U.S.
actions are tested, or proofed, by loading a cartridge with powder to generate
a substantially higher than normal chamber pressure. After firing this load, the action must
function as normal, and measurements of the action must not exceed a given
tolerance. This pressure is
substantially above normal operating parameters. The British just place a lubed
case inside the chamber to get identical results.]
I've enclosed a couple pics
of cases fired dry, and again wet, to illustrate what happens to the cases.
dry cases
wet cases
The rifle that shot these
cases needed the bolt locking lugs refinished afterward to be safe.
|