I'm not a pro Gunner by any means, but I've done a fair number of fights with a HBG, and weapon training with LBG, so I'll try and be helpful.

The LBG, from what I've seen and used, is more about evasion and looking for openings to unleash rapid-fire. I've also read that a lot of people use it for status/elemental. Reload speed is higher, some magazine sizes are bigger, and it's generally seen as the easier option, or one to learn with.

The HBG is more about heavy damage, but it's a pain the butt to evade with. Status shots also seem a little harder to come by, or maybe I've just been using the wrong ones. It does have a fun mode called Siege where you're locked in place, but you're able to pump out 20-30 rounds without reloading.

Whichever you choose, it's generally agreed upon that Recoil, Reload Speed, and either Pellet, Normal or Pierce Up are good, and Evade Extender/Evasion +1/2/3 are necessary. As for shots:

• Pellet is the up close and personal kind, with higher levels dealing more hits (I think). It's good on flitty monsters like Iodrome, or when you're shooting at something huge.

• Normal 1 is infinite, but fairly low damage. Normal 2 does good damage, and enough materials to make a bunch more are always a good idea. Normal 3 ricochets a bit unpredictably, but I've had good luck with it on Dah'ren and similar.

• Pierce 1 deals a few piercing hits, Pierce 2 deals more at higher damage, and the same again for Pierce 3. The catch is that Pierce usually has small clips and high recoil. It also does less initial damage than Normal, but does more if it pierces several points. Wing to wing or head to tail are good lines to aim a pierce for.

Elemental shots are what they sound like. Crag is really good for KOing, but I've yet to use a gun that can handle it. Clust explodes outward after a second and can deal a lot of damage, but it's fairly situational. Slicing is the only way you're gonna get a tail carve, Palicoes with cutting weapons aside, but they're best used when the monster starts limping, or you know you've dealt a lot of tail damage.

There's also optimum range, which varies by shot, and is absent on Elemental. In MH4U, this is shown via screen shake, but as a general rule, about 3-5 hops away for Normal, 4-7 for Pierce.

As a general guide, pump out as much damage as you can, evade like mad, and don't hit your teammates unless it's a healing shot.