DF Musketeer heavy pistol and Rifled Carbine.

[Phantasm]

Which book are you looking at? I'm eyeing Low-Tech, and the only "Rifled Carbine" there is a breechloader, but I'm unsure which pistol you're calling a "Heavy Pistol"; the one pistol with the same or very similar caliber designation to the carbine is the Highland Pistol. Damage in Low-Tech is 1d+2 pi+ for the Highland Pistol and 2d pi+ for the carbine.

That said, if the carbine you're looking at is a breechloader, early breechloading designs weren't able to fully contain the blast the way barrel-loaders were, leading to less propellant force despite using more powder. You might even say they needed more powder just to get the same force.