Continuity mistake: When Chucky and Andy are fighting in Andy's room Chucky has a pocket knife. When Andy kicks Chucky he drops the knife and it goes under the bed. Then if you look closely when the guy walks into the room you can see that the knife moved from under the bed to beside the chest in his room.
Factual error: When the school starts the war games and Chucky switches the paint rounds for live ammo and a few people get shot, this is impossible because those types of guns have been modified so they can't fire live rounds. All Chucky would have done is taken away their ability to fire anything.
Continuity mistake: When Tyler is going upstairs with the package that has Chucky inside, he collides with a boy up the top of the stairs (the boy was going down) and the package is knocked from Tyler's hands and falls down the stairs. In the shots of the package rolling down the stairs, the boy with whom Tyler collided should also be seen going down the stairs. Instead he is nowhere to be seen.
Plot hole: There is no way a military academy wouldn't teach their students the first rule of using a firearm: when you are given a firearm, you must always check if it is loaded and what kind of bullets it has. So there is no way Chucky could have switched the paintball shells with real bullets without someone noticing.