Your right. It can't actually be a shotgun do to the aerotech ranges for the weapon. A shotgun hitting something from a thousand kilometers away, not going to happen.

Even as a shotgun, aerotech would still have a use for it, though it would be a limited one.

A shotgun to a wing would really ruin a pilot's day. Plus, it'd probably be good for peppering battle armor that was in the open.

Frankly, I've always seen LBX's doing what the Annihilator did to me in MW3; chew armor off most of my mech all at the same time. An aerofighter coming in on someone's back is going to cause havoc.

Efficient, and best option? Probably not. Usable, certainly.

Why not?
Why not?

Simply BEING a "shotgun" like pattern does NOT imply a sudden loss in any respect of range or accuracy (which are the only things that distance would cause). Second of all, aerotech is HARDLY being hit by munitions at ranges of thousands of kilometers, and NEVER was in the rules as being hit that far away. LBX weapons range from approx 300-1000 meters or 0.3-1 kilometer, NOT 100 kilometers.

And, final thing, is that in ALL referances it calls the LBX shotgun LIKE. It does NOT mean that it shoots SHOT as does a shotgun, but instead that it has a spreading pattern of sub-munitions, much LIKE a shotgun.

And, final point on this, but why on EARTH would a proximity fuse unguided munition be more effective at hitting a long range target? Much like a shotgun, the spread would simply be adjusted. (10 sabot rounds aimed on a straight line together would still spread apart after 100 km).

i think the ac2s and ac5s as they are represented in the BT rules are a joke in general.

ac2s should be merged with machineguns into 1 category. i.e. much lighter ac2s. Regular machineguns shouldn't have enough punch to hurt armor anyway.  Have them take the same sort of role that the anti infantry smgs have on elementals.  I mean really, why would you want to scratch paint at long range with an ac2 when an lrm rack does that same thing better.

ac5 needs something a little more impressive that 5 damage for all the space and weight it takes up.  Especially when a small clan er laser does the same damage for half a ton and 1 crit. and a medium does more damage, has similar range, and only requires a few heatsinks to compensate.

its not until ac10s and 20s when ACs are actually worth using.

With double heatsinks as common as dirt in the current tech levels, nobody is really running into the same sort of heat issues that justified the use of the ac2s and ac5s in the first place anymore.

autocannons probably required alot less maintenance than lasers or energy based weapons.  They would also be alot less finicky in battle if they got jostled around a little.  small bore autocannons are like most small weapons, better in larger numbers.  if you have the range of an ac2 and alot of em you could do some decent damage.  Missiles work good at range to, but anti-missile systems are mounted on like every clan mech.  I read the jade falcon trilogy and they shot down most missiles fired at them without any huge problems.  So at extreme range, in a normal battlefield, you may want some trusty ac2s for long range.  alot of weaponry from what I've read in the books, is somewhat dependent on what is available, and the rest is on pilot preference.  people also seem to be throwing around modern real #'s for weapon calibers, and there really isn't the comparison unless that's really the size that the BT source says it is.  What you're trying to do is compare our weapons to sci fi weapons, and they may be based on our weapons(and so act a little bit like our weapons), but you have to understand that they aren't our weapons.

The 3025 weapon list from CBT were fairly well balanced.  Like Flying Debris said, it wasn't until double heat sinks were introduced that the balance went into the $hitcan. 

The basic way I consider the balance of a weapon was to take it's damage and then divide it by (weight + ammo + number of heat sinks needed to fire it cool).  Then, take that number and multiply it by 1/3 of it's maximum range.  Also, for every 2 Minimum Range (rounded down) subtract 3 from its maximum range. This gives you a good balance number for the weapon taking into account range, heat, damage and weight.

Examples:

Flamer: 2 damage / (1 tons + 3 (heat sink)) = 0.5 * (3/3) = 0.5
Small Laser: 3 damage / (0.5 tons + 1 ton (heat sink)) = 2 * (3/3) = 2
Medium Laser: 5 damage / (1 tons + 3 tons (heat sinks)) = 1.25 * (9/3) = 3.75
Large Laser: 8 damage / (5 tons + 8 tons (heat sinks)) = .615 * (15/3) = 3
PPC: 10 damage / (7 tons + 10 tons (heat sinks)) = .588 * ((18-3)/3) = 2.95

Machine Gun: 2 damage / (0.5 tons + 0.5 tons (ammo) + 0 tons (heat sinks)) = 2 * (3/3) = 2
AC/2: 2 damage / (6 tons + 1 ton (ammo) + 1 ton (heat sinks)) = 0.25 * ((24-6)/3) = 1.5
AC/5: 5 damage / (8 tons + 1 ton (ammo) + 1 ton (heat sinks)) = 0.5 * ((18-3)/3) = 2.5
AC/10: 10 damage / (12 tons + 1 ton (ammo) + 3 tons (heat sinks)) = 0.625 * (15/3) = 3.125
AC/20: 20 damage / (14 tons + 1 ton (ammo) + 7 tons (heat sinks)) = 0.9 * (9/3) = 2.70

LRM-5: ~3 damage / (2 tons + 1 ton (ammo) + 2 tons (heat sinks)) = 0.6 * ((21-9)/3) = ~2.4 (0.8 - 4.0 range)
LRM-10: ~6 damage / (5 tons + 1 ton (ammo) + 4 tons (heat sinks)) = 0.6 * ((21-9)/3) = ~2.4 (0.8 - 4.0 range)
LRM-15: ~9 damage / (7 tons + 1 ton (ammo) + 5 tons (heat sinks)) = 0.7 * ((21-9)/3) = ~2.8 (0.9 - 4.6 range)
LRM-20: ~12 damage / (10 tons + 1 ton (ammo) + 6 tons (heat sinks)) = 0.7 * ((21-9)/3) = ~2.8 (0.95 - 4.7 range)
SRM-2: ~3 damage / (1 ton + 1 ton (ammo) + 2 tons (heat sinks)) = 0.75 * (9/3) = ~2.25 (1.5 - 3.0 range)
SRM-4: ~5 damage / (2 tons + 1 ton (ammo) + 3 tons (heat sinks)) = 0.8 * (9/3) = ~2.4 (1.0 - 4.0 range)
SRM-6: ~7 damage / (3 tons + 1 ton (ammo) + 4 tons (heat sinks)) = 0.875 * (9/3) = ~2.6 (1.5 - 4.5 range)

Since criticals were rarely a problem in 3025 mechs and they only really mattered for the hugest ACs and ammunition, I haven't factored them in. 

Basically what this shows is that every weapon is more or less balanced against the others.  An AC/5 is roughly equivalent to a PPC, even though the AC weighs more and does half the damage, its the heat of the PPC that helps balance the two out.  Despite the superior range and damage of a PPC, the slighly extra heat, significant extra weight, and minimum range make it slightly inferior to the Large Laser.

An AC/20 is inferior to the AC/10 even though it does double damage for only 2 extra tons, this is because of the two-fold heat it produces and far inferior range compared to the AC/10.

The Medium Laser, as we all know, is the workhorse weapon on mechs.  It scores highest due to its excellent damage to weight ratio combined with good range.

While this formula doesn't take into account the freebie heatsinks included in an engine, it still provides an effective means of choosing which weapons to load onto a mech once the heat sinks are accounted for.  Hopefully this is helpful to someone other than myself.

I'll get to that.

The only way I can see for that to be true is if the LBX projectile is
proximity detonated.

A single space hex is 18 kilometers wide. An ultra autocannon 5 has a range of 12 space hexes, that means it has an effective range of 216km and that's only medium range in space. LBX 2's go out a lot further.

That would have to split apart a very very long way after firing. The only way to control that is if it's proximity detonated.

Note that bold word. Once they start spreading, it's not practical to stop them from spreading, especially in space.

They would start spreading only when they are almost on top of the target. That's why militaries use them instead of giant long range shotguns. I've never seen any evidence that LBX cannons fire more than one projectile. Even if they did, firing fewer rounds would still reduce spread.

no, rotaries were originally introduced in the cbt rules.

They were initially introduced by the Fedsuns if i recall correctly.  They only come in rac2 and rac5 sizes, though i have seen some fan created specs for rac 10s and rac20s, though i'm sure that'd be holy shit ridiculous and unbalanced as all hell.

I think the rules for them were that you could fire them regular ac speed with no penalty, but once you had them go at 2x 4x or 6x speed, you risked a jam, the jam chance increasing the more rounds you were firing.

Whether the original designers knew that rotary weapons are actually one of the most reliable weapon types as far as jamming goes, i do not know. (in a multibarrel setup all rounds are force cycled in and out whether they are duds or not, your main issue is actually heat build up rather than jams if say you are firing a gau-8, not such an issue on smaller vulcans)