LordKnightFandragon, on 19 May 2015 - 12:03 PM, said:
How does it even make sense an AC would fire that fast? To maintain a ROF like that for more then 10 seconds they would need an ammo bin the size of a battleship. And how does one think a 203mm shell(AC20), would even begin to fire that fast? 120mm? 105mm? Mechs are not as humungous as one thinks. Along with the armor, reactor, weapons, internals, there is no way ACs actually fire that fast and can carry that much ammo....
By high speed stream, im sure it means more like an auto loader system or revolver style reloading system that gives it a much higher RoF over like a Gauss. More like NAval cannons now, over a Gau-8 Avenger 203mm Minigun....
Stolen from this site:
http://bg.battletech...nnon-questions/
[color=red]DISCLAIMER AND WARNING:[/color] Before you start making objections I don't care what the fluff says, okay? The caliber and figures given in various books are random numbers pulled out of thin air by writers that didn't really know what they were talking about. I do know. The fluff numbers only give you a vague idea of the order of magnitude involved. My figures are based on game stats, wich trump fluff anytime, and my interpretation of what the original games designer were thinking, based on my knowledge of ballistics, artillery, and my own research. I don't care what the fluff says, all I am saying is that based on stats and physics, these are the most accurate, best fit numbers for this kind of sci fi weaponry. Please appreciate the work and effort I put into this to give you some plausible numbers before making objections. You can pick about precise numbers, but there is not much possible deviation from these parameters
I should add that in order to make the numbers fit, you should rename the AC/2 an AC/4 doing 4 points of damage, and the AC/5 should be converted to an AC/7 doing 7 points of damage. In between, there is an intermediate short barrel cannon, the AC/6, like those mounted in the Hermes and Wolverine.
In the real world, ballistic follows a curve where the bigger the caliber, the bigger the range and damage. For game balance purposes in Battletech happens the reverse, wich can be rationalized, these being burst firing weapons, that the recoil diminishes accuracy and range.
To have plausible Autocannons that are a best fit for the laws of ballistics and known ammo weights, ranges should be altered as well, AC/4, 7 and 10 should have the same range 18 hexes (same as PPC), AC/6 being a short barrelled gun would have less muzzle velocity and more recoil so having a range of 15 hexes (same as Large Laser), AC/20 should have a range of 12 hexes ( S 4, M 8 L 12). If you realize Battletech ranges are an abstraction for games purposes to allow for some maneuvering in game, and think for range purposes one hex is 100 meters, then you have average effective ranges of 1000 to 1500 meters, wich are reasonable engagements ranges for tank cannons. You can hit at longer distances than that, but as velocity decreases so does armor penetration. If Battletech ACs were single shot tank cannons, then their range would be greater, but no doubt inspired by modern ship cannon, the designers made their walking tanks wield burst firing cannon, wich rely more on multiple hits than single shot accuracy.
With those assumptions in mind, the large mass and size of autocannons in game stats are plausible. The sci part is the ability to fire a burst of several rounds in one or two seconds at most, and the ability to withstand the recoil. The concept is plausible as today, in the beginning of the 21st century, there have been developed artillery cannons that can fire several rounds in quick succesion. These use compressed gas cylinders to drive back the gun into position after its recoilm, faster than hidraulic pistons can. I envision that myomer bundles would replace the hidraulic recoil absorbers and recovery system, and work better than gas. The heat caused by the weapon is not so much from barrel heating but from the electrical power consumption of operating the reloading mechanism and the myomer absorbers that make possible burst firing.
With all these things in mind, here's the best fit solution to the game stats, after doing the number crunching, I am assuming a 2 second burst, wich gives cyclic rates of fire between 240 rpm and 120 rpm wich is reasonable enough compared with light antiaircraft guns of the 20th century or shipborne guns after WWII. A 1 second burst would be too high a rate of fire, a 1.5 second burst would still be reasonable, I settled on 2 seconds for simplicity and as a conservative estimate.
AC/4
1 Ton/40 shots = 1 game shot = 25 kilos, burst of 8 rounds 40 mm caliber, each round (cartridge + slug) = 2.5 kilos. 320 rounds per ton
AC/6
1 Ton/25 shots = 1 game shot = 40 kilos, burst of 6 rounds 50 mm caliber, each round (cartridge + slug) = 6.5 kilos. 150 rounds per ton
AC/7
1 Ton/20 shots = 1 game shot = 50 kilos, burst of 5 rounds 75 mm caliber, each round (cartridge + slug) = 10 kilos. 100 rounds per ton
AC/10
1 Ton/10 shots = 1 game shot = 100 kilos, burst of 4 rounds 100 mm caliber, each round (cartridge + slug) = 25 kilos. 40 rounds per ton
AC/20
1 Ton/5 shots = 1 game shot = 200 kilos, burst of 4 rounds 150 mm caliber, each round (cartridge + slug) = 50 kilos. 20 rounds per ton
Calibers are approximate, using even numbers for simplicity. Real word historical equivalents would be the following.
The best match and the one that was used as the baseline from where the other calibers were derived is the AC/10. It is obviously based on the standard tank gun of NATO at the time Battletec was designed in the early 1980s, the 105mm.
It is important to note here that all cannons are rifled ones. At the time Battletech was written, smoothbore guns hadn't come into widespread service. From the game background of the original 3025 set it is clear that aim is made by optical meters, technological decay and countermeasures prevent the use of laser rangefinders, so gunnery is still an art based on optical sights and guesswork. This rules out smoothbore guns as unfeasible, making them lostech.
Moreover, the basic round is an armor piercing discarding sabot slug (APDS) , you could also fire high explosive or hollow charge rounds from Autocannons, but that would recquire advanced rules based on those of Maximum Tech. For game purposes, assume AP as the basic load. You only need explosive rounds when dealing with infantry or blowing up fortifications and buildings. To have better accuracy with HE rounds you need the gun to be rifled. Hollow charges (like missile warheads) can also be fired by guns, wich would be a compromise between an armor piercing round and an antipersonnel. The spin imparted by rifling hampered hollow charge effectiveness when fired by guns, but this was solved around 1980 by the use of driving bands or ball bearings in the shell to cancel the spin.
The AC/7 (formerly known as AC/5) is analogous to the high velocity 75mm tank guns of the Second World War, specifically the German long barrelled 75 guns ( like the PAK 40 L48 mounted in the Panzer IV G marks )
AC/20 is a logical futuristic development of the AC/10. It would theoretically match with the 150mm tank guns in the drawing board towards the end of the Cold War projected for the next generation of tanks. It is important to note that there is doesn't exist a linear relation between the increase in caliber (wich means larger propellant charge hence more energy and speed) and the range and penetration (damage) of the gun.
This explains the jump from 10 to 20 points of damage , wich makes sense once you realize kinetic energy is a square function of speed.
However, this humongous weapon is pushing the technology limits. The large caliber means a big barrel wich cannot be as long and it doesn't optimize the force of the increased propellant charge. Short barrel and vicious recoil means the range is diminished, though it is much more powerful at short range. If it were a handgun, it would be a .44 Magnum snub nosed revolver.
The AC/4 (AC/2 in the game) is comparable with the antitank guns of early WWII, from 37mm to 40mm (British 2 pounder), or even better still with automatic antiaircraft guns like the German Flak 37mm or the Bofors 40mm, but with a bigger case with more propellant (about double size) and even more velocity. It is a fast firing gun with a very long barrel wich fires a high speed round with a modest recoil, wich gives it a long range, but due to the small size and mass of the round, its penetration (damage) is weak (though it certainly should do 4 points of damage, not 2!)
This makes the gun an ideal oversized machinegun for firing at infantry or aircraft, wich explains why the Jagermech mounts a pair. Only nitpicking is that the Vulcan gun should be longer barrelled, but everything else fits.
The AC/6 is an idea I developed to fit into 'Mechs wich have guns wich nominally are AC/5s but obviously are a different smaller gun, like the Wolverine and Hermes. It fits a niche between the AC/4 and AC/7 and is similar to the antitank and tank guns of the middle of the Second World War, like the German short barrelled 50mm gun mounted on the Panzer III, or the 57mm (British 3 pounder). It has a higher caliber than the AC/4, but a short barrel wich coupled with the higher recoil means its precision and range are lower. On the plus side, it is lighter, and despite it's higher rate of fire, it has more ammo per ton than an AC/7
The biggest difference with their historical equivalents is that Battletech autocannons fire bursts, not single shots, wich gives them awesome firepower, particularly when firing high explosive shells, but on the down side makes them high ammo consumption.
On a related subject, machineguns would be multiple barrelled Gatling guns in the 15- 30mm range similar to those that we have today, but wich are still peashooters compared with the autocannons.
Besides making holes in armor, one advantage of the autocannons is their ability to use special munitions for use against infantry, aircraft, or smoke and incendiary rounds.
Hope this was of interest.
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