Unlike the lance, the gunlance does not utilize "piercing" damage. Every attack involving the lance portion of the weapon strictly uses the cutting damage modifier.
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), and come in three different types: Normal, Spread, and Long. As the names imply, each type works 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. Using it will quickly dull the weapon. Whetstones are strongly recommended when using this weapon.