Ah didn't see the rapid fire part.. ill have to agree weight on the end of a barrel does seem to steady a rifle off hand but id say its mor of a muzzle flip thing than anything else... shorter barrels are usually used because of less vibration and less chances of defects in the rifling and lands themselves with that said sniper rifles have long enough barrels to sqeeze every last fps out of a round just to make it flatter shooting and a more reliable burn everytime (less differences between fps shot to shot) but with custom hand loads where you don't need 4000 fps to shoot 1600 yds a shorter barrel is usually prefered.. or atleast this is my understanding if more was better then bench rifles would have 30ft barrels on them..lol

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07/SOT2
NRA Instructor