While it looks like and sounds like a joke weapon, this is possibly the best Shelling Gunlance in MHFU. Large Pop Corn is the final upgrade of the Pop Corn.
It has a tremendous amount of green sharpness and small blue sharpness. One Wyvern's Fire takes away the blue sharpness, but the green sharpness is most commonly used by expert GL users for Shelling. The Shelling Lvl. of this GL is 5 - the highest Shelling Lvl. for all Gunlances. Plus, it has the Spread Type Shelling, which makes it even deadlier.
The Large Pop Corn is recommended for hard-shelled monsters such as Gravios, Basarios, and especially the White Fatalis, it has an impenetrable Armor Mode which you need to use any type of explosion attack to hurt it with normal damage. When it is in Armor Mode anything but bombs, gunlance explosions, clust, and crag are pretty much useless because every part of its body that gets hit is taken down to 10% unless using such explosions. GLs are recommended for those breeds because Shelling and Wyvern's Fire delivers a fixed amount of damage that cannot be reduced by their Armor Mode.