It depends on the user far more than the weapon system. You've heard the saying "Beware the man who owns but one gun?" Likely because he's good with it, knows what it can do, and how to best use it. I've seen AK 47 wielders fill the air with bullets, calmly taken down by someone with a 5 shot bolt action. Do you have cover and know how to use it? Can you estimate ranges and know the sight settings needed.? Does your ammunition match your sight settings?
Does your determination match your skill. Alvin York took out a Maxim nest with a 1917 Enfield, and forced over 100 armed troops to surrender, with only that rifle and a 1911. He was skilled, he was determined, and he knew what he could do with what he had.
I would comment that Custer lost only half of his command. The other half, with the same weapons, facing the same warriors with the same weapons, but kept together as a cohesive unit and dug in, maintained their postition until relieved. Tactics, not weapons, determined the outcome at Little Big Horn (Greasy Grass) A few months later, Nelson Miles and the 5th Infantry pushed Sitting Bull and his warriors over 20 miles at Cedar Creek. The 5th was well trained, Miles demanded firm discipline, and his tactics were superb, utilizing a moving square formation for much of the pursuit.