well, the explosion COULD be huge, but there are several options for that.
If we watch the chou-kamehameha that Gohan and Cell fire, when gohan finally did win, the beam didnt explode, it simply engulfed cell, and went out of the atmosphere.
The attack that Vegeta does to Recoome is a hybrid version of GG and FF. Some attack he learned before goku.
gallit gun should have more punch, i mean, come on, its as strong as Kamehameha.