Continuity mistake: In the scene when the Martins are in Charleston, Peter Howard is talking about his experience in the French and Indian War and how he lost his leg fighting in it. When the camera shows him standing there, he is holding a crutch under his right arm, seemingly supporting him, but it is his left leg that is missing. So he is actually giving support to his good leg while giving none to the missing one.
Suggested correction: It is the correct way to use one crutch. Crutches are usually used on the opposite side of the leg they must support. When one leg is partially weight-bearing, the crutch is on the opposite arm, when both legs are partially weight-bearing, two crutches are used each one moving along with the opposite leg. For more info, google "two-point gait."
Other mistake: When Martin and his younger sons attack the soldiers Gabriel sent to their camp, the body count totals 20. That includes the private who gets up and tries to run that Martin hacks to death. Later when Tavington is questioning the wounded private the Cherokee scouts brought in, he indicates he was in the fight. But Tavington states 20 soldiers were killed and the ambush shows 20 being killed. Where did the private come from?
Suggested correction: There are 21 soldiers in the group. Samuel kills one with a rifle. Nathan kills six with a rifle. Benjamin kills four with his rifles, one with a pistol, six with his knife and tomahawk, two with redcoat rifles, and shoots the injured man into the stream.