Explosionradius on Creeper

Hey guys,

i made a new Entity called Alpha Creeper

now i tried to override the function

where the Creeper explodes,

it didnt work ,

my code:

 private void func_146077_cc()
    {
        if (!this.worldObj.isRemote)
        {
            boolean flag = this.worldObj.getGameRules().getGameRuleBooleanValue("mobGriefing");

            if (this.getPowered())
            {
                this.worldObj.createExplosion(this, this.posX, this.posY, this.posZ, (float)(30 * 2), flag);
            }
            else
            {
                this.worldObj.createExplosion(this, this.posX, this.posY, this.posZ, (float)30, flag);
            }

            this.setDead();
        }
    }

The Creeper exploded but always had the same Radius,

any help?