Do not underestimate these guys.
Those men are Swiss. Those bulky uniforms can hide a lot of things...
“The Swiss Guard use traditional weapons, such as a sword and a halberd, as well as modern weapons such as the SIG P220 and Glock 19 pistols, the Steyr TMP machine pistol and submachine guns like the Heckler & Koch MP5A3.”
The men you see in those traditional Swiss 16th century uniforms are just part of the guard. Also, there are undercover guards everywhere at the Vatican.