honestly i think 7 shot hc is maybe a stretch, but here's what i have atm with adjusting the old opener
6 shot hc opener
he>HC>bfb>rs>hots shot->dex pot->etc
you might get an extra auto in buffed by he/bfb if you take gb off after 2nd clean shot doing it like this. with higher sksp (700+ with fey wind) you can get the slug shot buffed too (though a slug shot buffed by bfb/he+rs+gb is probably stronger than 1 buffed auto+slug, esp after 3.2 gear. so maybe best to turn gb off for the split shot instead.) not really much change here if 6 shots is the max. can swap he/bfb if desired.
7 shot hc opener - tight timing, turret aa reset
he>bfb>rs->hot shot->hc->dex pot->lead shot->etc
RS loses 1 GCD here (slug shot), but if 7 shot HC is the max then this guarantees it+a nice bonus of turret aa reset via hc cancel
7 shot hc opener - lenient timing, no turret aa reset
he bfb rs hc->hot shot->dex pot->lead shot->etc
same as above, but you save a bit of time if the timing is for some reason lenient enough that you can pop it pre combat. however you lose the benefit of having the turret fire once, then resetting its auto attack with hypercharge. so basically it is 400-500 dmg turret shot vs spending 1 less buff clipping into GCD during the pull. if you use HC pre combat it will only start shooting once you initiate dmg on the boss, which is 1.5s, as opposed to initiating hypercharged volley shots immediately if you are in combat already. right now with buff order HE BFB HC RS>GB hotshot, our HC turret has 13s left on the buff, but still gets 5 shots in.
7 shot hc opener - extremely lenient timing
(nogb) he>bfb>hc>rs->hot shot->gb on+dex pot->etc
if its lenient enough that we can keep our old buff opener by skipping the 1.5s delay on hotshot before the turret starts attacking, this may be the way to go. at high skillspeeds/fey wind buffed you still get the last slugshot in wf buffed by rs. it basically trades 1.5s precast on hotshot+a bit of extra GCD clip for RS buffed slugshot in wf and 1 auto.
also with gr being 200 potency, probably more important to have it off cd faster than rico now. it was already higher pps; i just preferred rico off cd for more uniform cd alignment w