Low/High-Tech Military Air Guns

[sir_pudding]

Originally Posted by Anthony

Exactly what distinction are you making between direct and indirect fire?

Direct fire is aimed at a target by the firing element. Indirect fire is aimed at an area by the FO (or at a pre-designated area or whatever). When I was a mortarman we could use the weapons in "Direct Lay" against visible targets. The gunsight is then aimed directly at the target rather than an aiming stake, and there is no FO/FDC needed. This doesn't make the weapon any less of a high-angle-of-fire weapon. It's totally analogous to arcing fire from archers or how siege weapons were generally used.

Battlefield archery targets an area rather than an individual, and if you had high tech comms you could perfectly well use it with a spotter and archers who were unable to see their target. Kinetic artillery is relatively inefficient because the minimum effective size for a gravity-powered dart is much higher than the minimum effective size for an explosive-powered chunk of shrapnel, but it's still artillery.

I never said it was useless. I said it was less useful. In my old job, within 25m was considered on target; with purely kinetic munitions that's not going to work.

[Anthony]

Originally Posted by sir_pudding

Direct fire is aimed at a target by the firing element. Indirect fire is aimed at an area by the FO (or at a pre-designated area or whatever).

That distinction largely has to do with comms; you can't use a FO unless the FO can communicate with the firing element in a timescale short enough to make his information useful.

Originally Posted by sir_pudding

I never said it was useless. I said it was less useful. In my old job, within 25m was considered on target; with purely kinetic munitions that's not going to work.

It could; you'd probably fire a streamlined sheaf of darts that would split shortly before impact, or at lower effectiveness you could just fire a canister of metal balls.

[sir_pudding]

Originally Posted by Anthony

That distinction largely has to do with comms; you can't use a FO unless the FO can communicate with the firing element in a timescale short enough to make his information useful.

You can also aim indirect fire at predetermined targets (which apparently was done with siege engines). Regardless, if the firing element is itself aiming directly at a visible target (rather than at a stake or something) then it's a direct lay.

It could; you'd probably fire a streamlined sheaf of darts that would split shortly before impact, or at lower effectiveness you could just fire a canister of metal balls.

Which is going to be less effective than explosives. Which is what I said. Again, I never said "useless". I said "less useful".

[Green-Neck]

Looking at the ballistics of the Girondoni, [150 grains at about 800 fps is 213 ft/lbs, about twice the energy of a .22 lr] and the .458 Quackenbush mentioned in one of the posts above [430 grains at 730 fps, 500 ft lbs] you can see air guns don’t have a lot of power.

If I remember correctly air guns were available thought most of the gunpowder age, but they were always expensive and low powered.

I can imagine bows and crossbows would remain popular.

If you wanted to push an air gun up to modern levels of power, whilst observing the low pressures available with stored air [A scuba tank is 3000 psi, a .223 round can be loaded up to 62,000 psi] it would have to be something in the order of a .600 calibre rifle firing a 900 grain bullet at say 750 fps for about 1100 ft/lbs. That's about equivalent to a .223, but a bigger hole [pi++] with less penetration [4d?]. At around 15 ft/lbs of recoil in a 10 lb rifle it should be aboutt recoil 3.

I think pushing those volumes of air you would need a backpack mounted cylinder [or ISO-tensoid or what ever floats your boat] tank to feed it.

[Flyndaran]

Bows and crossbows can't come close to a round a second like air guns. I imagine that would make a big difference for individuals rather than volleys.

[Green-Neck]

It's a little hard to project exactly what stats a gun might have as we don't have a defined TL from the OP. I'm imagining a late TL5 item, I suppose.

Given a Girondoni costs $1000, anything we create that’s more complicated will probably be more expensive. If we say a .600 cal pump action air rifle costs $1500, then that's ten crossbowmen you can equip for every rifleman [who has a half damage range of 60 yards!].

I suspect [especially in the absence of explosive artillery] that you would have some units equipped with air rifles as shock troops, and many other regular units with muscle powered ranged weapons.

[sir_pudding]

Originally Posted by Flyndaran

Bows and crossbows can't come close to a round a second like air guns.

Crossbows (and other sorts of spring powered launchers) certainly can be made to use a magazine and even to retain stored energy for subsequent shots. It was a dead end technology here, but so are air guns.

[Dammann]

re: Paintball guns and their applicability
The most up to date paintball guns shoot a .68 ball at around 300 feet per second. They employ compressed air, and use a regulated pressure to control velocity. The lowest pressure used is around 100 psi, the highest is more like 850 psi. Valve geometry has a lot to do with the proper pressure in a given gun.

Older guns use unregulated CO2. The output pressure was variable, between 800 and 1800 psi. Obviously, velocity from the guns is less consistent, but with the top safe speed of 300 fps, they were adjusted to shoot at a lower velocity so that pressure spikes don't hurt someone. Velocity was adjusted by varying spring force on a valve, restricting the diameter of air channels feedi the valve, or similar means.

I would call the older style TL 7, the newer TL 8. The newer style use solenoid valves to control valve cycles, which are controlled by printed circuit boards. The PCBs were obviously around during TL 7, but the solenoids didn't get small enough until the late 1990s.

TL7 paintball guns could cycle fast, but in practice, a RoF of 4 seems most realistic to the way most people could pull the mechanical trigger. A Perk might allow for up to twice that, but I only met a few people in my competitive career (encountering thousands of players) who could shoot a mechanical CO2 gun that fast. The accuracy was worse, because of variable working pressure; one just had more trouble with longer range shoots not going high or falling low.

TL8 paintball guns have a much higher RoF, with the electronics permitting burst fire and full auto modes, as well as relying on trigger pulls of 25 grams. Most computer mouse buttons require 150 grams, so we are talking about a VERY light pull. Even semi auto modern guns will shoot 10-12 balls per second without difficulty, and full auto might do up to the high 20s before mechanical difficulties start to assert themselves. The velocity was far more consistent, and out to 60 yards, the arc was pretty predictable, allowing for better accuracy at a distance.

CO2 tanks are about a pound and a half, allowing a couple thousand shots. the maximum output will be 1800 psi, but due to the CO2 changing phase, output drops as the ambient temperature changes or as RoF increases. Compressed air tanks are heavier, about 2-3 pounds, with a steady, regulated output of 800 psi easily achieved. They hold 4500 psi, 50% more than a scuba tank, and capable of powering 1000-1800 shots, depending on the design of the gun they're attached to. Different guns have wildly different efficiency with air. The best are shooting up to 2200 on the same amount of air that most guns will use for 1200 shots.

I would think that making the guns shoot a smaller, denser projectile at weapon speeds would divide the shots available by a factor of 4 or 5, but that's speculation. At 300 fps, a 3 gram paintball will usually break unprotected skin at less than 15 yards, and sometimes at longe distances. It doesn't do a HP of damage usually, but a hit in the eye is likely to blind that eye permanently. Cloth as heavy as denim will almost always reduce what would have been a bloody welt to a circular bruise. Neoprene will reduce it to a nearly invisible mark.

I hear that paintballs travel like an arrow. I am not very experienced with a bow, so I couldn't vouch for that, but it implies that a heavier, sharper projectile fired from an airgun could compete with a bow.

[Green-Neck]

Just out of curiosity:

A 2.64 gram paint ball at 300 fps = 8 ft.lbs

[Sam Cade]

There are commercial air guns (airbows?) that are shooting arrows in excess of 600fps.

That is enough juice to shoot completely through an elephant and kill the elephant on the other side.