My 17 LVSF is to be re-barreled with a Pac Nor barrel. As the gun will be used with a moderator of 5" in length, I want to chop the length down.
Would it be detrimental to accuracy if the barrel were taken to 18". Not too worried about velocity too much.

DW,

I don't think barrel length is a function of rifle accuracy. IMO barrel length is a function of velocity and perceived muzzle blast by the rifleman.

If anything it would probably help accuracy. At that lenght you might consider the 17 Mach 4/ 17 Fireball. It would be more efficient in the short barrel and burn 4-5 grains less powder which would be perfect for your moderator.