So my understanding is that tech firearms generally expend a charge for each shot made--so the more iteratives you have, the faster you need to put a new battery in your laser pistol. This leads me to a question about the Techslinger archetype's Covet Charge Deed:
"At 1st level, a techslinger can spend 1 grit point to use 1 charge fewer than normal when firing a technological weapon (minimum 0), as long as the weapon has enough charges remaining to be fired at least once. This deed replaces deadeye."
I'm uncertain as to whether the wording allows a Techslinger to spend that grit on every one of his iteratives if he likes--thus allowing an 11th level Techslinger to never lose charges on a tech firearm by way of the Signature Deed feat--or if the wording is intended to make one point of grit apply to an entire attack sequence, such that a Techslinger with Signature Deed (Covet Charge) would always expend charges equal to n-1, where n is 'number of attacks made'.
I would *like* to believe the former, but I worry it's too good to be true. On the other hand, the latter seems a bit underwhelming.
Since it doesn't say anything like "for a single round", and it's not described as requiring an action to perform, I would say it is per shot.
As for Signature Deed, it can be used for several "seems too good" options, so this is no exception.
Revan, I have played a techslinger in Iron Gods.
I can say from experience that the covet charge deed is extremely useful.
You are correct, signature deed would reduce your charge cost per round to be equal to the number of shots fired-1.
My android techslinger is built in precisely this fashion and that deed has probably saved me thousands upon thousands of gp worth of nanite canisters for my +2 Flaming Inferno pistol alone.
Signature deed is only 1/round. Works great for slow-firing heavy weapons tho. Rail guns anyone?