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.
From 1941 until 1946, the rank was equivalent to grade 2, ranking with gunnery sergeant and other technical ranks with which it shared its insignia. From 1947 until 1958, the rank was reclassified as E-6 and became the sole rank in this grade.