It would reduce it. The only way a P38 would have a chrome lined barrel would be as a result of aftermarket work, or by swapping in a postwar P1 barrel, which would reduce its value for having mismatched parts.
The P38 was manufactured during wartime, when simpler, less expensive ways of manufacturing things were sought out. Chrome lining - especially on a pistol barrel - would've been highly unlikely on a P38. If you have such a pistol, what you probably have is a postwar P1 pistol (aluminum slide, rather than steel), or else a P38 with a postwar P1 barrel swapped in.
10-100 USD or so
You will need a professional appraisal.
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
Samuel Colt
Ridiculous
@ 125mm