Repost Notice: This is a repost of what may be my first draft of this article. There may be minor mistakes reintroduced to it that were previously corrected in peer review. If you notice them again, please post about it so I can fix them!
Note: This article is primarily concerned with Inner Sphere vs. Inner Sphere tech play. It's very true that some clan weapons make some statements in this article untrue if used in IS vs clan games, but since most Light Gauss machines are used around Free Worlds League (and splinters thereof) space where clan machines are uncommon, this is not a huge concern.
The Light Gauss Rifle (“LGR†or “light gauss†from here on) has been the subject of a lot of scorn and mockery, with some people feeling it is one of the worst weapons in the game. This is only partially true; light gauss is one of the worst direct battle/main combat weapons... but used in moderation it is a meaningful tool/specialty weapon meant to deal with specific problems. This article will teach you what they are, what has gone wrong with the weapon's use in canon designs, and offer thoughts on better use in general.
What Can Light Gauss Do?
If we accept that light gauss is a specialized tool, you have to know which jobs it's best for. It's easy enough to know that the light gauss is a 12 ton weapon (with 16 shots per ton of ammo) that generates 1 heat and has ranges of 8/17/25 (Minimum 3), but on its own this doesn't mean much. You have to compare it to the weapons you'll be facing to see why it matters.
The most common long range weapons are LRMs, Gauss Rifles, and ERPPCs, reaching out to 21, 22, and 23 hexes respectively. How many times have you seen a 'line of gauss rifles', e.g. several assaults with lots of gauss and similar weapons parked on a hill? This situation is one of the most important ones light gauss can deal with. A light gauss machine with sufficient ammo can park at 24 or 25 hexes out and open fire on them while they cannot retaliate. You're firing on BTH 10 or so, but your opponent can't fire back unless they brought artillery or a weapon with comparable range to your light gauss. In other words, it can be used to force them to come out and engage you in a real fight.
Its other major advantage is its unusual range brackets; an 8 hex short range is 1 hex more than its rivals have at 7 hexes, so with careful movement you may be doing damage more regularly than they do. Of course, maintaining that exact 1 hex sweet-spot is hard, but a second one also exists; ERPPCs and LRMs have their medium range at 14 hexes, so you might be able to maintain hexes 15, 16, and 17 easily enough. Against gauss rifles, that sweet-spot exists at hexes 16 and 17 instead; this is still meaningful. Put another way, you may not be doing much damage... but in theory you're taking even less in return. In the unlikely event you face a clan ER Large Laser, you should note its long range is equal to yours (25 hexes), but the clan ERLL's medium range is 15 hexes; you still have a sweet-spot there.
Of course, neither of these uses are easy to do when your entire force is composed of light gauss units. These uses both require extremely precise movement and timing, and you won't be able to use them to their fullest on all your units if you bring too many light gauss machines.
Light Gauss is a tool, not a force-definer. You should only bring a few of this weapon to most battles.
What Is Light Gauss Bad At?
First and foremost, light gauss is bad as a main battle weapon. It weighs too much and does too little damage to gain its impressive range and ammo count per ton, such that if you use too many light gauss you won't have enough damage per ton to meet your opponents. As soon as they rush you (and encouraging this rush is one of the best things you can use light gauss for), you're in a real fight with them and if you brought too many of this weapon, you're likely to lose no matter how precise your movement is.
On its own, light gauss is also underwhelming at 'hole punching.' 8 damage is meaningful, but a little low for its range and weight; most of its peers do 10 to 15 damage at these distances. You should combine it with other supporting weapons to take care of this, and bring a machine that can capitalize on those gaps (such as a Hercules or Albatross, with their LB AC10s).
Simply put, light gauss is bad when there is too much of it in your army. It's a lot like a low-level D&D party consisting of only spellcasters, or a first-person-shooter squad of nothing but snipers; they're going to get rolled because they have no 'screen' in front of them to give them time to use their advantages.
How Many Should I Use?
Generally speaking, 1 or 2 per lance is plenty. 3 is pushing it into a strategic-emphasis role, and anything over that is probably overdoing it. Remember, you need some main battle units to take advantage of the light gauss units forcing your opponent to come out and fight you where you want him to be.
It's fine to spread that total out among multiple units, or put them all on one machine. A pair of TDR-9M Thunderbolts or a single Ontos LGR MML-refit will project about the same amount of firepower at 24-25 hexes, after all.
How to Make Good LGR Configs
This section only applies to building custom machines. To make a good LGR unit, you have to understand its major characteristics: It is heavy, but generates little heat, and hits out to very long range for “low-high†or “high-medium†damage. Since it's heavy, you can't add many more heatsinks onto the machine you're placing a LGR on... but you're not using many to start with.
In other words, ideally speaking you want one high-heat weapon (such as an ERPPC or ERLL) and one medium-heat weapon (such as a LRM-10, -15, or -20) to go with it. You may have to add one or two heatsinks to accommodate that, but on most units it should fit easily enough. If building a smaller machine, the medium-heat/missile weapon may have to go in order to have weight to fit the ERPPC/ERLL instead. Regardless, since it's only using 1 heat of your (presumably) 20 dissipation, you should add a long range energy gun to work with it. If weight permits, adding some missiles consumes the remainder of the heat curve very well while still adding a good amount of damage.
Try it yourself sometime. A 4/6/* or 3/5/* movement unit with an ERPPC, LRM-15, Light Gauss, an extra heatsink or two, and sufficient ammo can do quite well.
Responses to Common Criticism
“Okay, so you used light gauss to force my gauss units to move up for a real fight. Now it's light gauss versus regular gauss; I win.†– This is a common strawman argument against the use of light gauss, and it's built on the assumption that the light gauss user is stupid enough to define their force with the weapon. This is like assuming a LB AC/2 user is going to bring nothing but LB AC/2 units; why would they? A proper force brings one or two light gauss for the special situations above, rather than defining their entire army with it.
â€For three tons more you get a regular gauss.†- True, but this is both missing the point that light gauss is a special-situations tool (so you want to bring it on only a few units, making the ineffiency a bit less of a problem), and as MadCapellan has noted it is directly comparable to the LB AC/10 which weighs about the same as the light gauss. If you compare it to that weapon, suddenly it looks a lot more relevant for its size.
Canon Issues with Usage
One of the biggest reasons light gauss has such a bad reputation is that most of the canon machines using it are horrible. Truly stupid designs such as the “Marik-salvage Wolfhound†in TRO3085 attach a single light gauss and one ton of ammo with no other weaponry. Or there is the Griffin 5M and Shadow Hawk 7M, both of which either do not provide adequate sub-weapons to go with the light gauss and/or not enough ammo. Worse, these units have rotated out predecessors like the much better armed Griffin 3M on the FWL's front line allocation tables, meaning there are far too many of them replacing main battle units on a 1:1 basis in games where forces are created by RAT.
Light gauss is a decent weapon when used properly. The biggest problem is that most canon designs that are reasonably common or described as front-line machines do not use it well. They don't even come close, even if you forgive the whole idea that TRO/canon machines are not fully optimized. Take what you will from that conclusion, but know that much of the disdain for light gauss would likely go away if the weapon were used more effectively in canon designs.
Good Canon LGR Machines
There are actually a number of canon configs that use this weapon anywhere from decently to extremely well, and they're worth covering here.
BJ2-OE Blackjack Omni Alt. E: One of the best light gauss units around, equipped with one LGR, 1 ERLL, and 1 LRM-10. The LGR has 2 tons ammo (32 shots), and the LRM-10 has 2 tons (24) shots, while the machine itself moves 4/6/4 at 50 tons on an XL engine. So long as it has a decent bodyguard and screen, the BJ2-OE is an amazing fire support unit for its size and BV. It can do an average of 8 (LGR) + 8 (ERLL) + 6 (LRM-10 average) damage, for 22 damage... a knockdown threat out to 19 hexes. And with 32 shots, it can afford to plink at an enemy's gauss wall until they do come out to play. They might be willing to weather a few BTH 10 shots when you only have 16 rounds because you'll run out sooner or later, but when you have 32? It takes incredible patience to shrug that off.
Ontos Tank, LGR and LGR-MML variants: Moving 3/5/0, the Ontos LGR refit has 3 light gauss (with about 20 shots apiece, from a pool of 54 shots total) rifles at a low BV cost. It needs a bodyguard as well, but if you can provide that it's able to do up to 24 damage out to 24-25 hexes. This will definitely get most opponents moving! There is also a MML-refit version in TRO 3085 that replaces one of the LGRs with a MML-7, which can enable it to fend for itself against some of its most common counters.
T-IT-N11M Grand Titan: While it could be better, it still uses light gauss decently. The N11M Grand Titan can park at 24-25 hexes and plink at the likes of Thunder Hawks and so on until they come out, at which point your 4/6/0 movement and array of close combat weapons can be used. It's still going to be messy, but in this case you lose some raw long range damage in return for a risk-mitigation option that lets you eventually play to the Grand Titan's strengths. It's true that only doing 18 damage at long range is underwhelming for a 100 tonner, but the machine is still better than you might think; it's just not optimized.
TDR-9M Thunderbolt: A decent use of LGR, though it's only capable of doing an average of 17 (8 LGR + 9 average LRM-15) damage at range. Instead, what a TDR-9M user wants to do is plink until you come out for a real fight, then try to sweet-spot at 4, 7, or 8 hexes... these spots are good ranges for the ER Medium Lasers; Range 8 in particular is Short for your LGRs, but Medium for your ERMLs (yet your opponent's ERPPCs/Gauss/LRMs will be at Medium too, so this works out okay) and combined with its good armor means you can keep the TDR-9M in the fight for a good while. And when its ammo runs out, a trio of ERML and two punches or a kick is not too bad for continuing the fight.
Main Gauche Tank: One of the most inexpensive ways to field a single light gauss rifle in many formats (especially BV), there is a version that moves 4/6 and another that moves 6/9. Both are great for getting one light gauss into your army, and if your sole concern is using the weapon to force gauss walls to come out to fight you, this comes highly recommended. The Po Light Gauss refit tank does a similar role with the same speed, but more armor (and more BV, accordingly).
Hawk Moth VTOL: While some may say it's too slow to use safely, its relatively sluggish VTOL movement isn't too bad when you have this much range. So long as you can avoid specialized anti-air fire, this unit combines flight with good movement speed (maybe bad for its unit type, but still fast compared to many mechs) to offer good recon and range-plinking.
There are probably a few more machines that do it well, but these establish the basic idea. The HER-5ME Hermes II is often floated around as an example of good use of the weapon, and it may well be if you only have a few of them in your force.
Bad Canon LGR Machines
Too many to list, and they're why the weapon has such a bad reputation to begin with. Why bother? We all know about stinkers like the GRF-5M and TMP-3M2 already.
Conclusion
Light Gauss Rifles are a specialized tool, much like several other weapons in BattleTech. If you try to field a force consisting of nothing but LGR units, you're probably going to lose much like you would if your team consisted of nothing but LB AC2 machines. General misunderstanding of the weapon's purpose, and its misapplication in many canon machines, has lead to it being unfairly maligned.
Used in moderation however, it can solve a few problems that historically plague FWL armies against their neighbors (especially the Lyrans), and for this the LGR can have some real value on your team.
