If you have the ability to measure the bore at the muzzle you can determine if they have been cut down.
The constriction would have begun approximately 3" from the muzzle so you will need to be able to take a measurement at least 3 inches in.
Max constriction would occur approximately 1-1/4" from the muzzle, then parallel to end of barrel.
Barrels should appear to touch at the muzzle but can sometimes be cut 2" and still appear to touch.
If you poke around this site you should be able to find a diagram showing factory barrel profile.