This script simulates 10 000 shots fired non-stop with the given attack speed.
Every simulated second, the critical hit chance is increased with 3%
At the event of a critical hit, the critical hit is reset to the given base value right away (it does not wait 1 second as the skill in the game).
In the end, the average critical hit chance is calculated.
This script was written in about 15 mins. It does not take into account you walking or idle time to build up the sharpshooter further. This is a "worst case scenario" for the sharpshooter, imo.