If you keep a close eye on Captain Benson (Randolph Scott) and soldier Vogel (Leo Gordon) during their fight, there's a brief moment when Vogel has a fresh looking face when only a second before and after it was sweat and dust covered.
After killing the Indian, Denver Pyle's trooper holsters his rifle twice .
At about 44m., Scott knocks an Indian from his horse. As they are rolling on the ground, he (the stuntman) has his hat on securely. In the following shot, he is hatless.
After the battle, there should be two spare horses due the casualties in the soldiers. When Benson leaves, these horses are nowhere to be seen.
Around the 45 minute mark, a trooper shows the knife he says he took from a native who attacked Captain Benson earlier with a knife. The two knives are distinctly different models.
As Corporal Morrison (Harry Carey Jr.) saddles "Dandy", Lt. Col. Custer's second mount, he puts on an English saddle. US Calvary adopted McClellan saddles which remained in service through World War II. This was the wrong saddle for the movie.
Randolph Scott's character, Capt. Benson, continually refers to Custer as "the General," as do others during the inquiry in the commander's office. During the battle of the Little Bighorn, Custer was in fact a Lt. Col, his permanent rank in the Army. Custer's rank of General was a brevet (temporary) rank, bestowed upon him for a short period during the Civil War as a member of the US Volunteer Army. Once the war was over, he mustered out of the volunteers, received orders in the regular Army and reverted to his rank of Lt. Col..
When the troops present arms at the flag-raising at the beginning of the film, the soldier closest to the camera has a Remington Rolling-Block rifle, probably standing in for a Springfield Trapdoor carbine, with which the cavalry of 1876 was equipped. The Remington, though popular with the armies of many other nations, was never adopted in any form by the US military.
Custer left for the Little Big Horn from Fort Abraham Lincoln, not Fort Lincoln as depicted.
At no point does Benson send out scouts for his troop. Given the possibility of ambush, this is an unlikely event.
The Indian leader to whom Young Hawk speaks is not credited in the film. As it was a speaking role, the actor should have received a credit.
General Custer was a general at 23 and died at 36. Much lower in rank Captain Benson is played by 58-year-old Scott.
The filming locations in Mexico have smooth, wagon friendly, graded roads throughout the hostile Sioux territory; unlikely in the historic time-frame and true South Dakota location.
The fort featured in the film, with its Daniel Boone-style log structure, displayed architecture and design more fitting to the 18th century, not the late 19th century,
When Dandy appears on top of the hill, Benson tells the bugler to sound the charge. Not sure what the bugler played, but it was definitely not the charge. Cavalry mounts were regularly trained to come to the sound of certain bugle calls, but not the charge.
Near the end, when Custer's horse shows up, no one questions how it got there, or who might have been riding it.
After doing some online searching, a contributor found that Captain Tom Benson was a fictional character in what could've happened; surprised no one mentions that.