My understanding is that the key innovation in developing modern “quick-firing” guns was venting the expanding propellant gas back through the barrel to blow out bits of burning powder and chemical residue. The old-style muzzle-loading guns underwent a swabbing-out step during reloading in which a wet brush was run down the barrel to remove hot sparks and unburnt powder which might otherwise ignite the new gunpowder being loaded for the next shot, potentially killing or maiming the gun crew. “Quick-firing” guns did away with this crucial but slow step by blowing out the crud. The metal-jacketed cartridge-type rounds, loaded at the breech instead of shoved down the muzzle, also speeded things up in several ways – not having to measure the power under enemy fire, not touching the possibly-hot barrel with loose powder, easier handling, and allowed a tighter fit between barrel diameter and projectile; but supposedly the game-changer was the technical insight that one could recapture the propellant gases and putting them to work swabbing the gun itself.
Together with the breech-loading that pre-made metal cartridges made possible and the rifled barrels that were feasible now that one wasn’t muzzle-loading, artillery became faster-firing, more accurate, longer-ranged, and safer to use all at the same time – quite a leap in effectiveness.
It took me a second to realize you probably were talking about something like the Vulcan cannon, and not the AC-130 (a howitzer mounted in a cargo plane, essentially).
The closest thing to a direct- fire cannon that you’re likely to find today: the 2A45 Russian anti-tank gun. Fires a 125mm smoothbore gun using the same ammo featured on the T-64/72/80/90 generation of Russian tanks, which includes a high explosive round.
While guns like the M-119 can be used in direct fire, they’re intended for indirect fire. Stuff like the 2A45 is as direct fire as the ol’ Napoleons used at Gettysburg.
The Danish forces in Afghanistan have been using their Leopard 2 MBTs in the direct fire assistance role.
The tank trundles up on a suitable high point, way out in the open. As the opposing forces have nothing to spook a Leopard 2 at distances beyond a couple of hundred yards, there’s no need to worry about concealment - in fact, a nice, open field of fire is the safest. Infantry teams then go out to spot targets, pin them down with small-arms fire and call in direct 120 mm HE as needed. Pretty nasty.
What you’re looking at is an M-102 Howitzer (with a 40mm Bofors cannon in front of it, as well as two GAU-12s in the forward port side of the aircraft) mounted in a modified C-130 Hercules, known as the AC-130 Spectre.
We’d do similar stuff in Lebanon back in the 90’s, except for the fact that more often than not, it was the *tank *that spotted the targets, especially at night - a modern tank has much better night-vision equipment than any infantry squad can hope to carry.
What I find interesting is that with the deployment of the M982 Excalibur, artillery is more useful, but you need less of it, since the first round will take out the target.
Mortars can be used in what they call direct lay. It takes the FO out of the equation and the guns work on their adjustments themselves. The Fire Direction Center (FDC) isn’t even involved (though they may send them the firing data for future reference).
On the computer side, the ballistic artillery computers that are used now are really small. They’re hand-held palm pilot sized devices. Really neat things.
The U.S. uses mortars classified as light, medium and heavy. 60-mm is considered light, 81-mm is medium, and there are two heavy mortars, the 107–mm M-30 (most often called the "four deuce because of its 4.2 inch bore) and the newer 120-mm M-120. All but the 81-mm (M29A1 and M252) are smooth bore and fire fin-stabilized ammunition. The 81 (both versions) is rifled and spins the round to stabilize it.
The system most often used without an FDC is the lightest, most basic version of the 60-mm M224. Relatively short range, its rounds can be adjusted by observing the fall of the rounds and moving the tube left/right, up/down, very much like one would move the nozzle of a garden hose, until it strikes the target. It can also be used with a base-plate and sight system for predicted fire.
The larger mortars are almost always fired using FDC data and adjusted onto the target using corrections sent by an observer. Mortar fire direction, as with cannon, incorporates meteorological effects into fire direct computations when “met” data is available. The 4.2-in and 120-mm are both extremely accurate, even at long ranges (out to beyond 7,200 meters), and the 120-mm (M-120) fires precision guided munitions, in addition to a suite of standard mortar rounds like those used by other systems.
Mortars remain in our inventory for one reason–they are effective and responsive. Unlike artillery, they are organic to our infantry and armor organizations, meaning that the unit commander has complete control of his own indirect fires. Almost as important is mortars’ high rate of fire and the relatively light weight of their ammunition, compared to cannon systems. Those old movies where every infantryman carried his own ammunition plus two mortar rounds were accurate. Mortars are that important. For a maneuver unit commander, the only thing better than having good mortar crews is having good mortar crews and a direct support artillery unit, too. Mortars provide responsiveness, while the artillery adds depth to fires and can sustain them longer due to greater range, a wider variety of available types of munitons, more robust logistics.
In most “full-on” productions of the 1812 overture, they use the same modern artillery pieces that the experts have been discussing above. You can see that really clearly in this video from the Japanese Self-Defense Forces:http://www.youtube.com/watch?v=w-4SRvGUtn8
The Boston Pops used to do the same thing, but now I believe they’ve switched to producing the big booms through the simultaneous fireworks display. Or at least, that’s what I remember from the last time I was on the Esplanade for the Fourth.
