bullet bigger than barrel?

[meopilite]

i have a rifle that takes 30 caliper bullets. i bought 30 caliper bullets. just for kicks i held the bullet to the barrel. the bullet is actually bigger around than the barrel diameter. Is that suppose to be? i would think the bullet should slide right down the barrel...im new to this stuff.

[frizzellr]

The bullet is slightly bigger than the inside diameter of the bore across the lands. This is so the lands can catch the bullet enough to make it spin. Otherwise you would have more of a smoothbore than a rifle.

[eldeguello]

ORIGINAL: meopilite i have a rifle that takes 30 caliper bullets. i bought 30 caliper bullets. just for kicks i held the bullet to the barrel. the bullet is actually bigger around than the barrel diameter. Is that suppose to be? i would think the bullet should slide right down the barrel...im new to this stuff.

There are three diameters involved here. Two in the barrel, and the bullet diameter. On a .30 caliber rifle, the bore diameter is around .300", and the grooves are cut .004" deep, so the groove diameter is .308". The bullet should be .308" or so in diameter, so it takes some force to push it into the bore. When it is pushed into the bore by the powder gases, the lands cut into the bullet, causing it to spin as it goes down the barrel. If it just slid loosely down the barrel, it would not spin, and thus would not fly point-forward to the target. it would keyhole, and lose accuracy. So what you observed is the way it should be!!