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Weatherby Free Bore?
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<blockquote data-quote="Bart B" data-source="post: 344088" data-attributes="member: 5302"><p>What other size groups do they shoot?</p><p></p><p>I ask because it's rare that any Weatherby rifle shoots 1/4th MOA groups (all the time?) at 100 yards. To say nothing of the fact that few if any bullets typically shot in them (save match bullets made correct for their groove diameters) that well at 100 yards. To shoot 1/4th MOA at 400 yards, they'll have to shoot near 1/8th MOA at 100 yards; groups don't open up uniformly every hundred yards downrange past 100. </p><p></p><p>It's not an increased volumn in the case. Freebore is extra length of the throat for normal OAL rounds. With the rifling not engaging the bullet until its move a quarter to half an inch further, there's less pressure during this time. There will be less peak pressure with a freebored throat than a standard one where the rifling starts a couple hundredths of an inch from the ogive of standard bulleted cartridges. With freebore, one can put the same amount of a bit faster powder or, if case volumn permits, a few more grains of the same powder a normal chamber would get max pressure with.</p><p></p><p>It's the opposite as chambering a round with the bullet jammed into the lands. That will create higher pressure than if the bullet had a couple hundredths of an inch jump. That same load in a freebored chamber will have less peak pressure so one can add more horsepower inside the case.</p></blockquote><p></p>
[QUOTE="Bart B, post: 344088, member: 5302"] What other size groups do they shoot? I ask because it's rare that any Weatherby rifle shoots 1/4th MOA groups (all the time?) at 100 yards. To say nothing of the fact that few if any bullets typically shot in them (save match bullets made correct for their groove diameters) that well at 100 yards. To shoot 1/4th MOA at 400 yards, they'll have to shoot near 1/8th MOA at 100 yards; groups don't open up uniformly every hundred yards downrange past 100. It's not an increased volumn in the case. Freebore is extra length of the throat for normal OAL rounds. With the rifling not engaging the bullet until its move a quarter to half an inch further, there's less pressure during this time. There will be less peak pressure with a freebored throat than a standard one where the rifling starts a couple hundredths of an inch from the ogive of standard bulleted cartridges. With freebore, one can put the same amount of a bit faster powder or, if case volumn permits, a few more grains of the same powder a normal chamber would get max pressure with. It's the opposite as chambering a round with the bullet jammed into the lands. That will create higher pressure than if the bullet had a couple hundredths of an inch jump. That same load in a freebored chamber will have less peak pressure so one can add more horsepower inside the case. [/QUOTE]
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