Gunlances, also known as GL, are long, piercing weapons with a mechanism inside which can fire a blank round. Unlike Bowguns, the Gunlance cannot fire over distances; the Shelling ability can only be used from close range and reduces the weapon's sharpness for every use. The use of the weapon is largely similar to the original Lance. Like ranged weapons, Gunlances take ammo. They are able to charge up, indicated by the radiating energy at the tip of the lance, and dish out a strong explosive attack referred to as Wyvern's Fire.
The Gunlance has piercing damage (meaning it has a bonus damage in every piercing attack you do), and most of the monsters in the game are very weak to this kind of damage. It could be said that the damage goes almost directly through a monster. Meaning that while most weapons will have a damage reduction due to the monsters defense, a Gunlance user (as well as a Lance user) will have most of its base damage go unaffected.
The Gunlance provides the hunter with Shielding capability, as good as a Lance user due to the size of the shields. Lances and Gunlances have the strongest Shielding capability and can block some attacks that other shielding weapons would otherwise be unblockable.
The Gunlance has the Quick Draw feature, allowing the hunter to quick draw the weapon to shielding position just by pressing "R" button and then triangle while standing still, which can be very useful.
The Gunlance has the Shelling Ability. As the name implies, the lance has a gun embedded in it, which will activate with a press of a button. The best way to think about it is a really long shotgun with a bayonet. The shots are quite short ranged, but works well when linking it with the stabs of the Lance. You can see the amount of shells you have remaining on the upper left side of the screen and you can reload by pressing circle while defending with the R button, or by pressing "O" after a back jump.
The type of shells fired differ depending on the individual Gunlance. These usually range from Level 1 to Level 3 shelling (though some go as high as Level 5, Monster Hunter Frontier currently has Level 6 Gunlances), and come in three different types: Normal, Spread, and Long. As the names imply, each type acts differently.
Compared to a [Normal] type Gunlance, a [Spread] type's Wyvern Fire will have a wider blast radius, while a [Long] type is granted greater range. Regardless of level, a [Normal] Gunlance has 5 shots, [Long] types have 3, and [Spread] types have 2. However, [Long] and [Spread] shots inflict more damage than [Normal] shots.
The shelling feature has a downside; it burns through the weapon's sharpness, so using it will quickly dull the weapon. Whetstones are strongly recommended when using this weapon.
Gunlances come with an incredible explosion attack known as Wyvern Fire. This attack can be done by pressing the circle and triangle buttons while defending with the R button. The delay is usually 3 seconds and you have to be close for the attack to land. The downside is that after using it you'll have to wait for your weapon to cool down before being able to use Wyvern Fire again (cool down period is 110 seconds). Also the Gunlance's sharpness will dull after use (similar to Shelling) along with leaving you vulnerable to attack shortly after use. Wyvern's Fire is four times the length and four times the damage of its shell shot. It is one long blast that is divided into four sections, so if you hit a wyvern very close up you would do the full four times the damage, but if you hit it at half the length, you only do twice the damage of shell shot and so-on.
The Gunlances, just like the lances, can chain attacks. An example would be an attack from 3 single forward stabs to a shelling shot and repeat, or mix up with an uppercut (circle plus triangle) to diagonal attacks. See the video below for a great tutorial on how to do these combos.
Auto-Guard - Gunlance users can automatically guard incoming attacks with their shield without the need to press the button. It does not activate when attacking.
Gunnery King - Increases the damage of shells and Wyvern's Fire (see damage ratios).
Guard Inc - Increases the ability to block attacks that are generally unblockable (such as Gravios' Fire Beam).
Guard +2 - Decreases stamina usage and reduces health damage when a large attack is blocked.
Evade +2 - Increases invincibility frames while side stepping and back hopping.
Evade Distance Up - Increases the ground covered by all forms of dodging.
Autoguard - if the user has the Auto-Guard ability, one may cancel incoming attacks at any time by shelling with the button, and Auto-Guard activates even when shelling and Quick Reloading. It does not activate though when Wyvern's Fire is charging, during the slam attack, or after a Full Burst attack.
The Gunlance received a large boost to its moveset in MHP3, making it a more aggressive weapon in the game.
Gunlances in MHP3 can now do a Quick Reload, which reloads a single shell at high speed with the opportunity to fire a slightly delayed shot afterwards; this shot in turn can be chained into another Quick Reload for an easy infinite combo. This can be done by pressing after every shot.
The Full Burst is a new attack for the Gunlance. This occurs in certain combos, most commonly by pressing the button three times. The weapon slams downward to the ground after the third press of the button and fires all the current number of shells the Gunlance holds, creating a massive explosion that greatly damages all foes within its radius.
In addition, the forward stab can be comboed into a downward smashing attack; the smash can then be chained into a Wyvern's Fire attack or to a Full Burst.
Charged Shelling is also a new attack for the Gunlance, where it charges its shells first before firing at the intended target. This can be done in a number of ways; one of them is by holding the button and pressing the at the same time.
Please refer to the controls list for other Full Burst and Charged Shelling combos.