The Venezuela National Guard has adopted the Beretta Cx4 Storm carbine. My guess is that it is chambered in 9mm Luger (the Cx4 Storm is also available in .40 S&W and .45 ACP).
My initial reaction was that this is a strange choice of weapon for a reserve infantry unit, but after reading Wikipedia it makes more sense. The Venezuelan National Guard serve more in a gendarmerie / paramilitary police role than they do as a reserve infantry unit. The Cx4 Storm is a good law enforcement carbine.