[@Zeroth] I imagine the Bowling Bomb starts out as a softball-sized bomb, yeah. At the base level, it can get as big/wide as say a wheelbarrow, and have an blast range of... Maybe three cars parked next next to each other (at max size)? In its smallest size, yeah, it probably has the same force and power as a common, modern frag grenade, except no fragmentation.
At the highest level, I imagine it getting as big as maybe a pickup truck? And the blast being as large as an ACTUAL truck.

At bigger sizes it would have the force to knock down the walls of wooden houses, or shoddily made stone bricks. But it couldn't blast through things like actual castle walls or fortifications, it isn't that kind of bomb. Camilla might get a spell later on specifically amde for siege-warfare thougu. ^^

If this is too strong ir bit acceptable, I can always replace it with something else, just lemme know~