Most rifled firearms have a bore that is round, and has spiral grooves (the rifling) cut inside the bore. However, some guns (notably most Glock pistols) use a different system. The cross section of the bore is a polygon, with several flat surfaces. These surfaces twist in a spiral as you pass up the bore. It is claimed that produces a higher velocity than standard rifling, but it cannot be used with unjacketed lead bullets.
Which pistol? Most production pistols have a barrel length of 1 to 8 inches.
From mouth of barrel to where it meets the cylinder.
yes
A pistol is a single hand firearm with a short barrel.
No
125mm
Ridiculous
Samuel Colt
Frame barrel hammer
@ 125mm
From the end (where front sight is located) back to where bullet enters barrel.
No