For starters, when you use the charge attacks, you're rooted in place for a rather long time, more than enough for the enemy to wander off out of the shots. Honestly, the only useful part of the charge attacks is the final big shot, the one that goes through enemies.
I'd like to see the six shots removed and just have the one large shot, with a small increase in damage to it. Having the charge attack only produce the single powerful shot keeps in more in-line with the style of the gun, being more of a run-n-gun style, rather than the more rooted stance of the Autogun series. It'd also make the gun a bit more fun to use as well.
Well, besides that, the charge attack honestly is ok the way it is. It's kind of like the DVS, mean to be only used if enemies are incapacitated. Having the charge attack release one big shot (assuming it's just the bird and no pre-shots) would cause it to become a bit spammy, due to the large range or the bird. If it is just one slightly stronger bullet shot (not a bird), then the charge would be useless since a couple regular shots would outdamage that one charge shot.