The phrase "goes great guns" means to be doing well or making rapid progress. Antonyms for this phrase include "stagnant," meaning without growth or development, "struggling," meaning facing difficulties or obstacles, or "faltering," meaning to lose momentum or confidence. Other antonyms could include "falling behind," "plateauing," or "fizzling out." When something is not going great guns, it may be described as lackluster, feeble, or unproductive. It is important to note that sometimes progress is not always linear and setbacks or periods of slower growth can still lead to success in the long run.