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Old 10-29-2012, 12:21 AM   #21
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. . . A bullet fired at 1270 from a rifle with a 1 in 16 twist will rotate completely once every sixteen inches. So are yall saying that it rotates faster only because it takes less time to travel that sixteen inches?
I don't know that that's what we all were saying, but what you're saying sounds right.
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Old 10-29-2012, 12:33 AM   #22
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You need to think about it like this- YOU CAN'T CROSS THE SOUND BARRIER. A .243 will shoot a 95 grain bullet at 3000 FPS and when it get to about a 1000 yds it is at 1050 FPS, at that point it is worthless. A 22LR will shoot at 1250 FPS and once it gets to about 75 yds and 1050 FPS it is worthless. But a 22 LR that shoots at 1050 is good till it hits something.
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Old 10-29-2012, 12:36 AM   #23
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My experience with ballistics is moreso with terminals than externals. So please forgive me if I am not getting this.

A bullet fired at 1020 ft.sec from a rifle with a 1 - 16 twist will rotate completely once every sixteen inches. A bullet fired at 1270 from a rifle with a 1 in 16 twist will rotate completely once every sixteen inches. So are yall saying that it rotates faster only because it takes less time to travel that sixteen inches?
The RPM (revolutions per minute) of the round will increase with velocity using a given twist.

muzzle velocity fps x (12/twist rate in inches) x 60 = rpm of bullet
1020fps x (12/16) x 60 = 45900 rpm
1270fps x (12/16) x 60 = 57150 rpm
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Old 10-29-2012, 12:56 AM   #24
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So pretty much, yes!
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Old 10-29-2012, 01:02 AM   #25
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You need to think about it like this- YOU CAN'T CROSS THE SOUND BARRIER. A .243 will shoot a 95 grain bullet at 3000 FPS and when it get to about a 1000 yds it is at 1050 FPS, at that point it is worthless. A 22LR will shoot at 1250 FPS and once it gets to about 75 yds and 1050 FPS it is worthless. But a 22 LR that shoots at 1050 is good till it hits something.
I think whether or not it's worthless depends on what kind of accuracy you need; Minute of X ring, or Minute of Ribs, etc. No?
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Old 10-29-2012, 03:21 AM   #26
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the speed of sound is a majority of the time well above 1080fps it is only that low with high altitude and or cold weather because the air is thinner. at sea level and 70 degrees F the speed of sound is around 1165 fps. the trans-sonic flight is affect more in a .22 because of more drag or ballistic coefficient ( someone did say that) and the mass. A .308 weighs at least 4 times as much and streamed lined. Even in trans-sonic flight the .308 is more predicable.
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Old 10-29-2012, 03:53 AM   #27
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the speed of sound is a majority of the time well above 1080fps it is only that low with high altitude and or cold weather because the air is thinner. at sea level and 70 degrees F the speed of sound is around 1165 fps. the trans-sonic flight is affect more in a .22 because of more drag or ballistic coefficient ( someone did say that) and the mass. A .308 weighs at least 4 times as much and streamed lined. Even in trans-sonic flight the .308 is more predicable.
Yeah about 40 mph difference. But I guess that is a big difference when talking such small items.

I'd imagine that they state subsonic at 1080 so it remains subsonic at all "normal" altitudes under all conditions.
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Old 10-29-2012, 04:08 AM   #28
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yes sir.. and always being subsonic cuts out one of the many factors that take place on our little .22lr.

great talk we all had though

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Old 10-29-2012, 04:20 AM   #29
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Its why some folks like 24" barrels on their rimfires, as those older rifles with long barrels will slow the bullet a wee bit,
bringing some of the slower HV's to Standard/Match/subsonic levels...
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Old 10-29-2012, 04:32 AM   #30
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yes sir.. and always being subsonic cuts out one of the many factors that take place on our little .22lr.

great talk we all had though
Hold on a sec. <looks in her pants> Yup an inny.

I enjoyed our chat as well.
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