Under the gunslinger thread, at the very bottom under "Handgun Attack Speed" it says that ASI does not affect reloading speed.
ASI will noticably affect the reloading speed on guns, most noticable using a 0 ASI blitz charge as opposed to a Maximum ASI blitz charge.
Same works for normal attacks with say, an alchemer. This might make gunners think that reloading and shooting off the second / third / sixth bullet is bad because of this when this isn't a determining factor.
Once in a blue moon it is good to fire off the last of the bullets for burst damage (killing the mender quickly before it bubbles when you know how many bullets will kill it)
From what I have heard ASI doesnt affect the reload animation it just makes the gun move up and down faster which is part of what must be done when you reload.