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Long Range Hunting & Shooting
338 Allen Xpress, RL33 load development
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<blockquote data-quote="MontanaRifleman" data-source="post: 847302" data-attributes="member: 11717"><p>Yeah, I think I can get to 3200 with the nitrided barrel. The throat spec is .3085 x .200 with a 1*30 angle. The 230's barely fit in the 3.820 mag box about .010 off the lands.</p><p></p><p>In making the 230, Berger kept the same nose and tail as the 215, only lengthened the bearing. I think Berger tried to cram as much bullet in the Hybrid design as they could and make it work in a 10 twist. At our elevations they work OK, but I've read some other reports that guys were having some stabilization issues with them in a 10 twist. Using worse case inputs like 0 degrees temp and 0 pressure altitude @ 3200 fps, the Berger twist calc gives an SG of 1.33 which is marginal for terminal performance. With more normal inputs like 20* and 3000' altitude, the SG goes to 1.55 which is perfect. Upping the velocity to 3400 fps only boosts it to 1.58 I'm finding out that velocity doesn't have a huge affect on stability, whereas temp and altitude do.</p><p></p><p>So bottom line is, to make a hybrid style bullet in a 250 gr would require a 9 twist. Heck, I would like to see them do a 260. I would consider 30/338 LM Imp build for that.</p></blockquote><p></p>
[QUOTE="MontanaRifleman, post: 847302, member: 11717"] Yeah, I think I can get to 3200 with the nitrided barrel. The throat spec is .3085 x .200 with a 1*30 angle. The 230's barely fit in the 3.820 mag box about .010 off the lands. In making the 230, Berger kept the same nose and tail as the 215, only lengthened the bearing. I think Berger tried to cram as much bullet in the Hybrid design as they could and make it work in a 10 twist. At our elevations they work OK, but I've read some other reports that guys were having some stabilization issues with them in a 10 twist. Using worse case inputs like 0 degrees temp and 0 pressure altitude @ 3200 fps, the Berger twist calc gives an SG of 1.33 which is marginal for terminal performance. With more normal inputs like 20* and 3000' altitude, the SG goes to 1.55 which is perfect. Upping the velocity to 3400 fps only boosts it to 1.58 I'm finding out that velocity doesn't have a huge affect on stability, whereas temp and altitude do. So bottom line is, to make a hybrid style bullet in a 250 gr would require a 9 twist. Heck, I would like to see them do a 260. I would consider 30/338 LM Imp build for that. [/QUOTE]
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338 Allen Xpress, RL33 load development
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