Emmet has a whole arsenal of directed energy weapons in "period-accurate" chassis. When going back in time you want both plausible deniability and firepower.
Thus the "Blunderbuster"—disguised as a flintlock pistol, but packing, shall we say, a bit more pep. Perfect for mixing with pirates and other high seas scalawags, which is exactly what he intends to do.
Here we see him putting it through its paces... which mainly means going through a sequence of dramatic poses.
Artwork by Alexander Johnson [https://alexjohnson93.carrd.co]