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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Big Seven Case Capacities
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<blockquote data-quote="dwm" data-source="post: 29884" data-attributes="member: 1136"><p>dbhostler</p><p></p><p>I have an 11 twist barrel.</p><p></p><p>168 SMK shoot fine, 168 Bergers keyholed but I didn't try running them real fast, they may have stablized.</p><p></p><p>I was not really interested in shooting 180 grain bullets when I bought the barrel. I thought 168 SMK and 162 SST/AMAX would do fine for my intended use.</p><p></p><p>I was concerned with barrel/throat errosion and wanted the 160+ grainers to go real fast. So I went for the 11 twist.</p><p></p><p>If one were to go with a barrel that was 34 inches long and get some serious velocity, I think a 10 twist would be fast enough, even for big bullets. </p><p></p><p>Would be interesting to know what twist the other 7MM RUM/Weatherby users have.</p><p></p><p>I know that a lot of people will be thinking 9 twist is right for the real big bullets, but I think the real fast twist contributes to the burned out barrel/throat thing. If you can get them to higher velocities they will stablize with a slower twist.</p><p></p><p>The bigger the bullet and the faster the twist the harder it is to get them spun up and pushed down the barrel. Something to do with overcoming the rotational moment of inertia of the bullet and the added friction due to a larger bearing surface. I think this holds the fire ball closer to the throat for a longer period of time. This is purely a thought exercise and I have no experience or proof to back it up though.</p><p></p><p>Doug</p><p></p><p>[ 12-14-2003: Message edited by: dwm ]</p></blockquote><p></p>
[QUOTE="dwm, post: 29884, member: 1136"] dbhostler I have an 11 twist barrel. 168 SMK shoot fine, 168 Bergers keyholed but I didn't try running them real fast, they may have stablized. I was not really interested in shooting 180 grain bullets when I bought the barrel. I thought 168 SMK and 162 SST/AMAX would do fine for my intended use. I was concerned with barrel/throat errosion and wanted the 160+ grainers to go real fast. So I went for the 11 twist. If one were to go with a barrel that was 34 inches long and get some serious velocity, I think a 10 twist would be fast enough, even for big bullets. Would be interesting to know what twist the other 7MM RUM/Weatherby users have. I know that a lot of people will be thinking 9 twist is right for the real big bullets, but I think the real fast twist contributes to the burned out barrel/throat thing. If you can get them to higher velocities they will stablize with a slower twist. The bigger the bullet and the faster the twist the harder it is to get them spun up and pushed down the barrel. Something to do with overcoming the rotational moment of inertia of the bullet and the added friction due to a larger bearing surface. I think this holds the fire ball closer to the throat for a longer period of time. This is purely a thought exercise and I have no experience or proof to back it up though. Doug [ 12-14-2003: Message edited by: dwm ] [/QUOTE]
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