217 mm
No. The frame does.
The M9 pistol uses an "oscillating Block" locking system. At the moment of firing, the slide and barrel are locked together. They are both driven rearward by recoil- but after about 3mm of travel, the barrel tips down, unlocking from the slide, which continues to the rear. For additional information, do a web search for 3-23.25, the manual on the M9 pistol.
Which pistol? Most production pistols have a barrel length of 1 to 8 inches.
The M9 uses a locking block action very similar to the Walther P38
@ 125mm
Condition 2, does not apply to the M9 Service Pistol.
Follower, Floor Plate, Magazine Tube, Magazine Spring, Retaining plate, Locking Block Plunger.
The M9 is a standard 9mm round. the M9 is actually a .355 caliber
9mm
Beretta made a LOT of different 9mm pistols. However, if you are asking about the M9 pistol used by the US Army, it is about 8.5 inches long.
One would not need to purchase an M9 pistol. One may want to purchase an M9 pistol so they can go target shooting with it. Target shooting is a hobby many enjoy.