Upgrades and modifications
AR15s are as accessorable as legos. You can add on everyone accessory you can possible think of to an AR. There have a been a few funny spoof photos of people putting can openers and headlights on their guns, but it’s not far from the truth. There are reasons to have rails on various parts of a firearm, but most people won’t need anything more than a mount for optics, foregrip and a flashlight. Military applications open a whole new can of worms.
You can take a standard AR15 lower and snap out and snap in an M4 AR15 Upper or swap it out for a longer range 20 inch barrel A2. There are now a few caliber changes you can make with just pushing two pins out and snapping on a new upper. Ever since the ammo price increases, the 5.45×39 upper made from Smith and Wesson has gained enormous ground within the shooting community. You can get your money back after putting 2 or 3 thousand rounds through your gun and compare that to 5.56 prices which might cost close to what an upper costs you per thousand rounds.