I recently tested this theory in a Tokyo Marui Hi-Capa carrying a 7" inner barrel.
Testing was done with a well used but cleaned Nine Ball (Prometheus / Laylax) 6.03mm inner barrel versus a brand new PDI 6.01mm.
The result?
The PDI 6.01mm yielded slightly higher velocity (as expected), but it surprisingly also provided marginally tighter groupings at 31 feet.
The pistol was held free-standing in isosceles stance, aiming aided by a Doctersight RDS.
