Pressing: Manufacturing may be one of your biggest expenses. There are a few different ways this can go down: If you have a distribution deal, your distributor may pay for manufacturing up front and then recoup the costs from sales.
When a opening takes place (someone retires) then the Marine Corps promotion board looks at the available candidates and their fitness report scores to fill the vacancy. So make sure you have excellent scores and reports. I picked up SSgt (E6) in 10 years. Gunnery Sergeant (E7) may take up to 14 to 16 years.
Gunnery Sergeants are E-7's that have been in the Enlisted rank for a long time and mastered their skill/job set and display superior leadership qualities. A Gunnery Sgt is generally in charge of a company size element. The job a Gunny holds varies per unit. It is different then the Army's E-7. A gunny in an arty btry is the senior cannoneer in the unit. He is the go to guy for problems.