OBT Forum

What's the deal with ACs?  I've seen several explanations for how ACs are rated.  The one that makes the most sense is the number corresponds to the bore diameter in mms; AC/2 = 20mm, AC/5 = 50mm, etc.  The other I've seen says that all ACs have the same bore and the number corresponds to a fired busrt; AC/2 = 2 rounds, AC/5 = 5 rounds, etc. and they all hit the same body location.  The first makes sense, the second is just stupid.  Also, like Halvagor stated, what's the deal with the ranges, they make no sense ballistically.  Unless you're saying the smaller caliber ACs are firing high velocity, flat shooting rounds while the larger caliber ACs are more like low velocity, arching fire howizters or mortars, you don't have an arguement.  But you say, ACs have a saving grace; low heat.  That's great, but they also have a huge weakness; ammo dependence. 

How ACs work hasn't changed much over time.  FASA 1707, BattleTech Master Rules had the following description for Autocannon:

Autocannon
An autocannon is a rapid-firing, auto-loading weapon that fires high-speed streams of high-explosive, armor-piercing shells.  Light autocannon range in caliber from 30 to 90mm, and heavy autocannon may be 80 to 120mm or larger.

Autocannon are also available in advanced LB-X and Ultra versions.

This entry makes ACs sound like chainguns such as the 30mm version carried by the AH-64 Apache, which would probably make a RAC into the roughly-similar GAU-8A Avenger carried by the A-10 Warthog (which, incidentally, can't jam; that's why I say it's similar to a chaingun even though the ones on the Apache or the 25mm Bushmaster series on APCs/IFVs are single-barrel weapons). 

The Tech Manual, FANPRO 35103, meanwhile, gives us this:

For what amounts to one of the most basic combat systems on the modern battlefield, autocannons (often abbreviated as ACs) are a broadly varied class of rapid-firing, auto-loading, heavy ballistic weaponry -- gigantic machineguns, in other words.  With calibers ranging from 30 to 90 millimeters on the lighter end, to as much as 203 millimeters or more at the heaviest, most autocannons deliver their damage by firing high-speed streams or bursts of high-explosive, armor-defeating shells through one or more barrels.  While caliber and firing rate can vary greatly, four main classes have emerged over the centuries, setting the standards by which all other ACs are rated, based on their relative ballistic damage.  At the lightest end is the AC/2 class, followed by the long-time standard AC/5, then the heavy punch of the AC/10 class, and finally the brutal, close-in AC/20.

Sadly, the descriptions of LB-X weaponry -- not to mention the mechanics of switching between "cluster" and "solid" ammo -- make it seem like LB-X weapons are of the one-giant-barrel / one-big-shell variety, rather than the AC's fairly-consistent burst-of-shells description.  If you really want to "spread" your ammo at the cost of having only some of your many projectiles actually hit, that should be either a mechanical change (like old four-wheel-drive) or a software one (like switching paintbrush styles in photoshop) which adjusts the "spread" of the shells.  But there I go, injecting reality into a game again.

Well as long as the feed system isn't based on the one out of the Soviet T-72 then it should be fine.

As for the LB-X, basically a big shotgun or the old artillery equivalent of grapeshot or modern equivalent of beehive rounds, cluster and solid should be two different types of ammo coming from two, seperate magazines.  That means if the mech only carries one ton of ammo it has to be a mixed load to be able to switch between ammo types.  Otherwise you have to have a round that does both, like canon (no pun intended) apparently implies, and has some type of WWII-era radio proximity fuse (and even those could be manually set for the distance they exploded from the target).  So apparently there's a switch in the cockpit to tell the round to stay solid or turn on its proximity fuse before the round (or rounds) are fired.

Oh, and I threw the problem with ACs in the MW computer games in because this thread is supposed to emcompass all "problems" with all things BT.  So if you've got a problem with the Mech Warrior cartoon then by all means let us know.

Well, if the LB-X cassette system is anything like the Enforcer's "clips," then switching ammo types could be as easy as having the feeder draw from the specific location. Think of a double hopper on a paintball gun. Pretty easy tech that uses a single barrel.

My switch selector (electronic) double feed hopper would disagree. It's actually pretty simple, even with a clip. The feed just slides from one position to the next. As it slides it covers the opposing clip. Works pretty well with an electric feed or spring fed clip.

Of Course LOL

The issue with LB-Xes isn't so much dual-feed ammo supply as the fact that even a standard autocannon, per just about every description, is already shooting the equivalent of cluster munitions.  The grapeshot/canister/beehive/whatever comparisons just reinforce that rather than a derivative of the mini-gun-esque autocannon, LB-Xes are really a throwback to the slow-firing big-bore guns similar to modern day MBT cannon (this is emphasized by the frequent description of these specifically as smoothbore weapons, as every major MBT design that isn't British uses a smoothbore cannon, and the Brits are finally catching on). 

Now, BT tries to skate around this problem by treating weapons as in the same "class" rather than dealing with specifics, thus we might presume that the "lighter" AC/2 or AC/5 could be either a quick-firing 30mm rotary cannon or chaingun (which the above descriptions would support) or a slower-firing high-velocity 90mm cannon; the single 90mm shell would be doing "roughly" the same damage as the burst of 30mm shells.  Moving form that 90mm to an LB-X version makes sense, but the generic autocannon description has always said that most of the ACs are rapid-fire chaingun- or rotary-cannon-esque weapons...you know, much like how the RACs are supposed to be.

Much of the official artwork, on the other hand, has depicted the autocanons as MBT guns on robots, even though this goes against the definition of most autocannons, per the sources cited above.  Of course, RACs are even more foolish-looking...

Just my two cents, but I've always read autocannon as "auto-loading cannon", i.e., a gun that doesn't require a manual loader.  In weapon terminology, the term automatic has always referred to the automatic cycling ability of this nature, and though in modern parlance it has come to imply a rapid fire capability, it does not necessarily mean such. 

While the original fluff stated they were "rapid fire", just about everything else in the game, be it fiction, art, and rules seem to heavily support the opposite.  If a rotary autocannon is just a faster firing autocannon, why do it's shots scatter all over the body of the target but a standard AC delivers it's shot in a solid clump?  If the AC/20 is a rapid-fire weapon, why does it look like a trench mortar and most 'Mechs it's found on?  The autocannon's rate of fire may be rapid, but it's likely only rapid in comparison to today's tank guns.