Pact of the Bullet
Ethereal as ther weapon may be, your patron understands the difficulty of spells in melee range. You may use your action to make a melee spell attack. The damage is 1d10 force damage plus cha modifier. This also bypasses the material component for booming and green flame blades. If you make the booming/green flame blade attacks using the pistol, you may add an extra damage dice to the secondary function.