Defending the riverbank, Jack's machine gun jams and he leaves it for a rifle. Moments later he's back shooting the Browning. Really poor editing.
During the initial night-time battle against the attacking Japanese forces (8:49),one Japanese soldier is clearly seen firing a German made Maschinenpistole MP40. No such weapons were in use with the Japanese Imperial Army during WW2.
Wearing his greens, Jack has two rows of ribbons but contrary to Marine regulations, no marksmanship badges.
Although the film takes place in 1942-1943, Camp Pendleton is flying the fifty star (post 1959) flag, not the forty-eight star design, which would have been correct.
The TWA airliner shown during the bond sales tour is a Convair 440 which did not fly until 1947.
The TWA airliner that is shown flying the men around the country is a Martin 404, which was not introduced into TWA's fleet until July 1951, six years after the war ended.
Although the film takes place in 1942-1943, all of Marilyn Devin's hairstyles and clothing, as well as that of the other females in the cast, is strictly 1967.
The helmet cover worn by the Gunnery Sergeant on Guadacanal is out of place. Camouflage helmet covers were designed during September 1942 (during the Guadacanal campaign) not introduced until later campaigns fought by the USMC in the Pacific in WW2.