For the heightened precision perk, it provides accumulative enhanced damage when constantly striking targets (up to 6 stacks) and expires when you cease aiming down sight or hitting targets in the last 5 seconds.
However, when you end the shooter stand, the stacks are fully gone, even if you are holding the right-click, which is the aiming down button. It makes these two perks ineffective when paired together because you can’t carry a large stack after doing burst damage or quickly build up your damage stacks.
I’m not sure if this is a planned feature or a defect in the design of these perks, but one thing is certain: if the shooter stand does not destroy the stacks, the overall performance of the musket may be substantially enhanced.