"David R Brooks" wrote in message
...
Yes, I know this isn't strictly metalworking, but there are plenty
of gun people here.
A howitzer fires, with elevation 45 degs. So the shell exits,
pointing upward at 45 degs., spinning. When it hits the target, it
is (to 1st approximation) falling at 45 degs., but the spin should
have kept it pointing upward. This means it would be flying
sideways-on.
This sounds wrong to me, but where is the error?

General Hatcher was concerned about gun range safety back when troops
fired rifles up at towed aerial targets and investigated how bullets
fall by firing upward at a Florida lake where he could observe and
time their splashes.

https://books.google.com/books?id=Dt...down&f=fa lse

He wrote of coastal artillery mortar shells "At angles of elevation of
less than about 85 degrees, the action of the air keeps the shells
flying point forward, at higher elevations they are likely to fall
base first."

The yaw resistance of a projectile is a balance between the greater
air pressure on the nose and the gyroscopic stability from spin. The
rifling twist usually isn't much more than enough to keep the bullet
pointing forward.

https://en.wikipedia.org/wiki/Alfred_George_Greenhill

http://bulletin.accurateshooter.com/...pin-a-problem/

https://en.wikipedia.org/wiki/External_ballistics
"Mathematical models for calculating the effects of drag or air
resistance are quite complex and often unreliable beyond about 500
meters, so the most reliable method of establishing trajectories is
still by empirical measurement."

The empirical methods as calculated by radar-equipped WW2 US
mechanical fire control computers were good enough that for example
the battleship USS Washington straddled the Japanese battlecruiser
Kirishima with the first salvo at 8,400 yds at the Second Naval Battle
of Guadalcanal. Japanese damage control records show that 20 of the 56
shells were hits although at the time Washington claimed 8 or 9. The
others were simultaneous adjacent second hits or fell slightly short
and raised visible splashes before penetrating the hull underwater.
Other navies lacked our radar and computers and averaged less than 2%
hits.

I studied fire control and torpedo computers to learn to build
scientific instruments.
https://en.wikipedia.org/wiki/Ball-and-disk_integrator
Long range shooting is nearly impossible in densely forested New
England USA so I can't tell you more than the above about ballistics.

Now that the HMAS Sydney and Kormoran wrecks have been found, have you
heard any new details about their desperate battle?
-jsw