You dont need to change for a tightbore most Ics barrels are about 6.04 so changing to a 6.03 wont do much .
A 6.01 is a bad idea .
You dont need to change for a tightbore most Ics barrels are about 6.04 so changing to a 6.03 wont do much and a 6.01 is a bad idea .