The character Ellen Abramowitz, a Lieutenant in the British Army, does not know how to pronounce her own rank. British pronunciation is, literally, "Leftenant", for complex historical reasons. This is the case in the British Army and the Royal Navy, and in the Royal Air Force rank of Flight Lieutenant.
When Beckett is firing at the rebels to distract them while Chandler works his way down to the camp, and Beckett keeps shooting a rebel who keeps getting back up, two different sets of shots are inter-cut. In one set the rebel has an assault rifle (AK74 or similar) with a magazine in it. In the other, his rifle has no magazine. So the magazine keeps appearing and disappearing.
On the firing line at 'Camp Lejeune', a Marine can be seen firing a Truvelo Armory CMS Sniper Rifle 12.7x99mm not the Barrett M107 .50BMG the Marine Corps uses. This movie was filmed in South Africa, and many guns in the film were sourced from there, the Truvelo included.
The optics the Marines are using on their Colt M4 Rifles are a mixture of nonmilitary optics. The correct optics should be the Trijicon ACOG, Aimpoint Comp M3/M4 or EoTech 552. They Optics on their rifles appear to be a low cost BSA and other non-approved variants.
When they are talking to the Congolese army and explaining the difference in the firing and workings of the automatic rifle, the soldier takes the gun and shoots at a downed tree. When the camera pans from right to left behind him, the gun is pointing at the ground, yet bullets are hitting the tree in the distance.
When it showed a fired brass case being ejected from a M16 rifle in .223 caliber, the case that ejected was rimless and the one that hit the ground had a rim on it. It looked like a .303 caliber case.
The film is set in Congo, but in an early crowd scene a woman is carrying a bag from Shoprite, which is a South African supermarket chain.
The film is set in Congo, but in an early crowd scene a woman is carrying a bundle wrapped in a wraparound skirt with the word "SWAZILAND" on it. The word is reversed because she has the cloth inside out.
All vehicles are right-hand drive but the movie is set in Congo so they should be left-hand drive (the movie was shot in South Africa where right-hand drive vehicles are the norm).
In Sniper 3,which was released in 2004 the character of Thomas Becket was unmarried and had no children. Some how in this film, which was released 7 years later, Becket has a son who is at least in his early 20's.
At the end Beckett meets a SOCOM officer dressed in a Navy or Coast Guard uniform who identifies himself as a Major (O4 pay grade). Actually the Navy or Coast Guard equivalent to Major is Lieutenant Commander. Also, the "scrambled eggs" on his visor would indicate that, at minimum, he would be a Commander (O5).