In the final battle, the closeups of the machine gun showed U.S. .30-06 ceremonial blanks, with red wads in the cartridge, in the ammunition belt while firing. When the gun was at rest, ball rounds, with projectiles in the cases, were in the belt.
The machine gun in the final battle was a "composite" made to have some features of the Hotchkiss, however the receiver was an American Browning 1917.
Pvt. Grenier addresses Sgt. Corey as "Sir" in the first part of the film. It is never appropriate to address a non-commissioned officer (sergeant in this case) in this manner.
The camouflage uniforms worn by the American raiders are not WWII military camouflage uniforms. They are wearing commercial duck hunter suits that were sold in the USA after World War II. They are based on wartime USMC camouflage uniforms and bear a passing resemblance.
The M1 Carbines were with post War modifications, they had bayonet lugs.
The field gear, packs, canteen covers, pistol belts, etc. were of mid 1950's vintage. The color was a dark green, not used during World War II.
Late in the film, a Japanese soldier yells "aray!" after being hit over the head. "Aray" is actually a Tagalog, not Japanese, expression meaning "ouch". The production hired Filipinos to play the Japanese roles.