On Mon, 20 Aug 2007 09:17:05 -0700, mlcorson
wrote:

Is it possible to arm a round by hitting on the ground? How are the
rounds armed? In the movie "Saving Private Ryan", they slammed the
butt end of the round and threw it.
========
Bear in mind that the following is based on my experience with US
Infantry weapons many years ago, and things do change. I was
also at Carter Carburetor where we made hundreds of thousands of
BLU3 and mortar fuses.

The usual US practice for mortar shells at that time was to have
a spring loaded inertia pin that retains another pin that rides
on the bore making the round "bore safe." In operation the round
is drop fired and the inertia pin driven back releasing the bore
safe pin that then rides on the inside of the barrel until the
round clears the barrel. Some little distance ( a few feet) past
the end of the barrel the bore safety pin pops out and the round
is armed.

In Vietnam because of the very high and dense jungle canopy in
many areas, a number of mortar crews killed themselves attempting
to shoot through it [with a quick or super quick fuse, even
brushing a twig or a leave will be enough to set off a round
after it is armed and an air burst is the most dangerous kind ]

An improved mechanical delay fuse was developed with a spring
loaded paddle wheel that spun around for a few seconds and then
armed the fuse. More than likely some sort of electronics are
now used.

A contributing factor is the need to [generally] remove
propellant "increments" to adjust the range in addition to
adjusting the inclination of the tube.

One of the "tricks of the mortar man's trade" (not covered in any
FM I know of) is to attach additional increments left over from
prior shorter range shots to gain those few additional yards of
range. This is similar to tipping the powder can to make a 357
out of a 38, and most definitely is *NOT* the place to apply the
rule "if somes good, mores better, and too much is just enough."
Last words here may well have been "Watch me get 20,000 yards
easy with this round."

The explosion might also be another example of a lack of quality
control or a difference in weapons design philosophy which
stresses cost and producability over operator safety, or some
other bonehead move such as using a faster [rifle] powder in the
increments if the proper propellant had been lost or damaged,
similar to replacing Blue Dot by Bullseye on a weight for weight
basis because you are running low on Blue Dot.

Unka' George [George McDuffee]
============
Merchants have no country.
The mere spot they stand on
does not constitute so strong an attachment
as that from which they draw their gains.

Thomas Jefferson (1743-1826),
U.S. president. Letter, 17 March 1814.