From: Bruce Kalin (convoy@mtaofnj.us)
Date: Mon Mar 20 2006 - 19:48:19 PST
Jim,
My squad had an 81 mm mortar. Same principle as the 60. The squad leader
Jim Stead wrote:
>
We used to throw these into the campfire to really heat up our C rations
:-) Not exactly according to rules but, they sure got the fire going.
had the chart and the sight. Everyone else was a lumper. One got the
tube, two got the base plate, and the rest carried the round.
Bruce
> The lift charge used to lift a mortar shell is incremented so as to
> provide a more precise control of the aiming of the shell.
>
> Think of it this way...A maximum lift charge with the appropriate
> angle might land a shell miles into the distance. Now, what happens
> should you want to land one just a few hundred yards away?
>
> You could just elevate the mortar higher...maybe even to 89 degrees
> (almost vertical) but then, with the maximum lift charge, your shell
> is going way, way up into the air and is influenced by wind, heat
> rise, etc, etc. Crap...it might even land on you! Aiming to fractions
> of a degree so as to hopefully land within dozens of yards of your
> enemy would be practically impossible. This is a terribly inacurate
> and unreliable way to lob a mortar shell. In fact, it's not done.
>
> Instead, you keep the gun to a typical firing angle and simply reduce
> the "lift" charge. Instead of flying miles, the shell now flies only
> hundreds of yards.
>
> To hit a target reliably, there needs to be a combination of angle and
> lift. One is not more valuable than the other. However, the proper
> combination will provide accurate fire. This is where "the tables" (or
> "experience") come in to play.
>
> The increments for these rounds contain smokeless powder. It's like
> pulling the bullet off a pistol cartridge and pouring the powder into
> a plastic baggie. Not the most ideal thing to carry in your pocket,
> but it isn't going to do ANYTHING but burn fiercly in your pocket
> should it be ignited.
>
> DETONATION is a process where the energy of an explosion exceeds the
> speed of sound. It is damaging in all cases and is useless to us
> unless we want to destroy things.
>
> DEFLAGRATION is a process where energy is released from a source at
> less than the speed of sound. It is "ooph", "thud", "bang" and "lift".
>
> A firing gun uses deflagrating propellants to launch a projectile.
> It's true that smokeless powder has more energy than Black Powder.
> However, it is absolutely wrong to think smokeless powder
> detonates...because in that case you would be standing next to a 60mm
> pipe bomb. Place a stick of dynamite in a 2" steel pipe and stand next
> to it while it goes off. Notice a difference?
>
> BTW, smokeless powder as well as mortar increments are all perfectly
> legal to own. They are not explosives, they are propellants.
>
> The propellants used for mortars are fast burning, like pistol
> powders. They burn fast, but in a large tube (compared to a pistol
> barrel) only manage to fill it with enough pressure to "lob" a shell
> out. It's similar to the HI-LO effect in a 40mm grenade cartridge.
> This is not pistol, rifle, or artillery gun pressure. Those kinds of
> pressures would blow the little thin-walled mortar apart.
>
>
>
>
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>
>
>
-- Bruce Kalin East Coast Convoy Coordinator USMCMTA, MVPA, MTANJ, NCMVPA
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