I don't watch 24 (yeah, I know, I'm an anomoly) but based on pictures I've seen, it appears to be a H&K some pictures, a Sig in others, and in one particular picture, he is carrying a Glock. I suspect perhaps he uses different guns at different times.
Jack Bauer has used many different kinds of guns throughout the series. He has used a Glock, a SigSauer, rifles of sorts, etc. He also has used different kinds of weapons, such as grenades of sorts, and even his fists. He was trained to be in the Special Forces, so he knows the element of surprise. This is why he also uses miscellaneous weapons, such as his mouth.
Sig Sauer p-228
Chiappa Rhino 20DS
He acually Used multiple kind of guns in the clone wars He use the dual pistols the long blasters and the normal blaster.
Bill asked Jack, "What'll we use for lighting the fire?"
Colt SAA
Epinephrine (adrenaline).
Bauer vapor x60
Bauer Total One
Steven Stamkos uses a Nike Bauer stick which is black and the Bauer sign is in the middle and it is white. the blade and the nob tape are white
a bebe gun
Bauer Supreme total one nxg
A gun
he uses Bauer TotalOne as of 01/25/11
can you use any kind of an 22 shell like an long or short shell in an 22 gun
.338
Revolver
It was a .38 caliber Colt Cobra revolver.