The current state of C4 is quite a dire one. It does less overall damage, has less ammo reliability, has much less speed, and a lot less range than Orb. For 2 points less, that’s quite the downgrade.
In practice, this is ever more visible. Throwing C4 at someone who is pressed against a wall most likely wont kill them. Trying to use the weapon anywhere but indoors (due to the range of the throw) makes the weapon’s usability even lower, as its range only rivals the knife and Double Barrel (but DB can 1 shot with ease!). Lastly, its damage is even less paralleled with the other pistols, which for 3 less points, are infinitely more flexible and usable than C4 is in most situations.
Personally, to rebalance C4 (into a more beloved C5), these are the changes I think are applicable. First, increasing the “throw” projectile’s velocity by about 1.5x will increase its range in less close quarter situations, as well as decrease the TTK of an average engagement. Second, increasing max damage range (when exploded) to start cascading after a 2 block radius (after the center block) would allow the weapon to be more potent against someone who’s on the other side of a wall.