Posted 07 October 2013 - 04:24 PM
I'm using an LB-X Atlas brawler in 12-mans; a D-DC with two LB-Xs, 3 SRM6s, and two medium lasers. It works very well; the LB-X is accurate enough at close range to place most or all of its damage on a single location - and the increased rate of fire makes it a monster. Not to mention, you can still glom onto other people's work do your part to harass at longer ranges for kill assists, too.
What you have to realize with the LB-X is that it is a close-range weapon. Sure, it's got the fourth-longest effective range in the game; but that's because it's damage is limited more by its spread than it's range increment. I can typically put most of my shot group on a single location on any slow-moving target - and all of it on one location if I'm shooting at another large, slow 'mech. This means that the the superior rate of fire (and heat efficiency) allow me to not only compete well within my weight class, but to stomp lighter opponents flat.
To put it another way: in order to truly compare the two weapons loadouts, you have to compare how much overall damage (dps) is being done to the amount of focus damage being done (pinpoint.) The dual LB-X setup wins the dps contest - the combined damage exceeds a single AC/20 by a whopping 60% - which is good, because you're using just under 60% more tonnage, too. The AC/20 is the winner in pinpoint damge per shot - so to figure out which is really doing more good, you have to figure out how much of the LB-X's superior dps is actually making it to the location you want to kill. This is, strictly speaking, impossible to do scientifically on the forums: too much depends on your opponent's speed, the engagement distance, the size of his hitboxes, etc. What you can do scientifically however, is determine how much of your close-range damage needs to be pinpointed with the LB-X in order to compare - that's easy: 62.5% That's the point at which your superior dps no longer punches through the enemy's armor faster than the AC/20. At middle ranges or longer, you're not going to get that. But at close range (say 270 meters or less) on a large target, you absolutely can. It becomes more difficult to model at longer ranges, since the AC/20 is losing damage, but at 540 meters (where the AC/20 is doing half damage) you would have to place only 31.25% of your dps on the desired location to break even - again, not likely to happen, but it gives you some basis for comparison.
Now, I know that someone is going to pull out the tired old chestnut about how "torso twisting" magically negates any amount of superior dps. Every time I have encountered this argument, it hasrelied on exaggeration and oversimplification - I do not find it convincing. While the superior pinpoint damage of the AC/20 is important, In practice two LB10/X ACs will often outperform it on a 100-ton BattleMech. In short, even if I just sit there and wait for him to twist back before shooting again, I'm still getting the same pinpoint as he is, close-in - and I can twist away before he can fully come to bear, forcing him to make a more difficult shot through my superior screen shake. Add in the bonus damage from two crit-seeking weapons once armor has been breached, and the LB-X combo is a clear winner - the AC/20 comes close, but no cigar.
In the end, dual LB-Xs are superior as a close-range weapon to the AC/20 - and they should be! Not only are they a shotgun, with all that implies, but the combination of two autocannons weighs 60% more! To be sure, the Ac/20 is good, too; in fact, I'm certain it's a superior skirmishing weapon - but for going toe to toe and duking it out, the dual LB-X is a stronger contender.