LCDR Pete Duckman (Anthony Hayes), a US Navy SEAL on McMahon's staff carries a Olympic Arms K23B Tactical as his main weapon. Most likely, this is the same gun that was previously seen in Skyfall; the common denominator is that both productions sourced weapons from the same armory (Bapty & Co., U.K.)
The Beretta 92FS, standing in for the U.S. Military issued M9, is the standard sidearm carried by US forces in the film, notably by General Glen McMahon (Brad Pitt).
A paratrooper version of the M249 is seen carried by US Marines. The machine gun is seen with a paratrooper barrel and a full stock instead of the collapsible version.
Error creating thumbnail: File missingM4A1 carbine - 5.56x45mm with M203A1 grenade launcher - 40mmError creating thumbnail: File missingCole about to launch another grenade. This carbine has been incorrectly assembled using the bottom half of the KAC RAS handguard with only a single rail rather than the correct top half which contains the side rails. Also note that this particular carbine is not an actual M4; it notably has a thin "pencil barrel" with no step for an M203 mount, and the flattop upper receiver appears to have been manufactured by cutting off the carry handle from an earlier upper.