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.
A Gunnery Sergeant in the infantry is typically in charge of coordinating logistics for a company-sized group of Marines (approximately 180 personnel.) Junior Gunnery Sergeants usually serve as platoon sergeant for weapons platoons.