From:	Justin Kim <jlkim@******.COM>
Subject:	Re: Firearms 101
Date:	Thu, 30 Sep 1993 08:49:41 -0800

>Smoothbore: Don't think that there aren't reasons to go smoothbore. The only
>examples I am aware of in modern life is tank guns, like the 120mm smoothbore
>used by the Germans and now us on our Main Battle Tanks. Because rifling acts
>as resistance on a round, it slows it down. If all other factors are equal, the
>velocity of a smoothbore-fired round will be higher than that of a rifled-fired
>round. This is important in tank warfare, where (among other things) you're
>trying to get as much force (of which velocity is a component) as possible in
>order to penetrate armor. Many tank rounds have fin stabilizers on them to make
>up for the loss in accuracy.
><Stuff deleted>
>J Roberson

Actually, one reason why many tank cannon are not rifled is because
of the type of ammunition that serves as the tank's main anti-tank round.
The depleted uranium discarding sabot rounds used work (basically) by
forming a jet of molten metal which punches through the armor of the
target. The spin imparted on a APFSDS-DU round by a rifled barrel creates
centripital (it's early. I can't spell when it's early :-)) force which
decreases the effectiveness of the jet by pulling it apart. I would
imagine that this would also apply to HEAT rounds which also create a jet
to penetrate armor.

On another note, I have a question about the dikoting of barrels
comments that have been bouncing around lately. I don't have shadowtech in
front of me, so if it's in the book, just give me an "RTFM, stupid" and
I'll shut up.

It isn't clear to me why dikoting the barrel of a gun would negate
the effects of the rifling. Does harder=less friction? One thing that
some (I wouldn't say many-I don't know for sure) gun owners do is chrome
their barrels. The chroming gives the barrel a very hard surface that
resists corrosion and wear better than plain steel. I know that chrome =/=
dikote, but the principal seems the same.

Also, would giving a "pebbled" or sandblasted-type finish (not
really sandblasted, I imagine that it would take quite some time to
sandblast dikote) or similar rough finish allow the barrel and its rifling
to work correctly?


Justin

--------
Justin Kim jlkim@****.edu Defense Analyst
Science Applications International Corporation San Diego, California USA
I'm paid to have opinions. If SAIC wants them, they had better pay me for them!
"The perimeter sensors are picking up subspace ocilations. What the hell
does that mean?" -Major Kira Nerys, DS9