Explosive Runes on a weapon?

[Barstro]

So-This weapon deals 6d6 points of concussive force damage upon striking an opponent. The wielder is immune to the explosion by the weapon but all creatures and objects within 10 feet are susceptible to this damage.

How's that sound?

Expensive. You are looking at the equivalent of 6 +1 abilities, but with the better "force" instead of "flaming", etc. Even if you look at it as a Burst type of weapon, it's two of those, but always on instead of only criticals. On top of that, you want it to affect everything in a radius except the wielder and the weapon.