What's your budget? What type of shooting and optic set up are you looking for? Irons, reflex, red dot, acog, 1-4, 1-6, 1-8, or a higher powered scope. Stay away from cheap stuff imo, that includes bushmaster. They do not have the same reliability or accuracy. I recommend building one. Out of the box I recommend Colt as the cheapest option, around $800. Beyind thst you can look at stuff like lmt, bcm, etc. After that stuff like building is imo the best option.