A makeshift camp believed to have been used by gang members was found by police during an exercise in Carenage on Tuesday night.
Police said members of the Western Division and soldiers raided several areas between 3 pm and 8 pm.
They went to an area known as the ridge at Jones Street, Carenage, where they found the camp.
A Glock 19 pistol with a silencer and four rounds of ammunition were found inside.
Police also found three rounds of 7.62 ammunition and a pair of binoculars along the river in Upper Abbe Poujade Street, Scorpion Alley.
No one was held for these items.