the fluting decreases weight an stiffens a barrel, aids in cooling. the flutes on the optima serve no purpose since they arent very deep! more for looks than anything, the barrel differance is your choice by adding your bullet and say 3 pellet charge you have turnned you 26 inch barrel into a 22-23inch barrel so the 29 inch will become a 26 inch barrel and there for give you a slight increase in velocity
