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375-408 CheyTac (Kirby Alert!!!!!!) question
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<blockquote data-quote="Black Diamond 408" data-source="post: 120814" data-attributes="member: 1563"><p>From my testing and that of others, the 300MK will stabilize from 9.5 through 11.5 twists, currently Barney Lawton is using the 11.5 twist rate on the 338 Big Bear bbls. Also the same 11.5" twist is being used on the 375-408 version. This is the heaviest bullet you can put through this twist(300mk). As Kirby has stated, the 10 twist is right in the middle, i see no difference in accuracy from the 9.5 up to my bbl's 11.25 twist, using 300MK's But if you go heavier, the 11" twists will not stabilize the bullets. I built my rifle around the 300MK bullet, I wanted to "spin" the 300MK bullet the same amount a Lapua does at 2900fps, my rifle speed was 3350fps. Running the bullets through the 9.5" twists had the same effect but more spin rate, groups are well under .5moa.</p><p></p><p> lighter bullets also shoot very well, but impractical unless you want to incinerate what your shooting at. The case capcity is too large for the smaller weights. I wish there was a 325gr bullet, i feel this would be a very good balance for speed and BC. A match-hunting bullet with a BC of .850-.900 surely would extend the range of the big 338's, 2700 yards or more before the transition takes over. Currently the 300MK will put out BC's just over .800 The 350gr Wildcat bullet may very well excede that with more testing, that i can not do in my personal rifle due to the twist rate. The speeds of the 350gr bullets are in the 3200fps range, 338cal. This is where the 338 cal rifle will put down the 375 version, lack of propper hunting bullets. From my calculations, the 300MK will out perform the 350grn bullet to about 1200yds, then the 350gr 338cal bullet will take over for balistics and retained energy. Make no mistake, the 300mk has made numerous Elk kills past 1800yds.</p><p></p><p>From the desk of a rifle builder, no expert on exterior balistics!</p></blockquote><p></p>
[QUOTE="Black Diamond 408, post: 120814, member: 1563"] From my testing and that of others, the 300MK will stabilize from 9.5 through 11.5 twists, currently Barney Lawton is using the 11.5 twist rate on the 338 Big Bear bbls. Also the same 11.5" twist is being used on the 375-408 version. This is the heaviest bullet you can put through this twist(300mk). As Kirby has stated, the 10 twist is right in the middle, i see no difference in accuracy from the 9.5 up to my bbl's 11.25 twist, using 300MK's But if you go heavier, the 11" twists will not stabilize the bullets. I built my rifle around the 300MK bullet, I wanted to "spin" the 300MK bullet the same amount a Lapua does at 2900fps, my rifle speed was 3350fps. Running the bullets through the 9.5" twists had the same effect but more spin rate, groups are well under .5moa. lighter bullets also shoot very well, but impractical unless you want to incinerate what your shooting at. The case capcity is too large for the smaller weights. I wish there was a 325gr bullet, i feel this would be a very good balance for speed and BC. A match-hunting bullet with a BC of .850-.900 surely would extend the range of the big 338's, 2700 yards or more before the transition takes over. Currently the 300MK will put out BC's just over .800 The 350gr Wildcat bullet may very well excede that with more testing, that i can not do in my personal rifle due to the twist rate. The speeds of the 350gr bullets are in the 3200fps range, 338cal. This is where the 338 cal rifle will put down the 375 version, lack of propper hunting bullets. From my calculations, the 300MK will out perform the 350grn bullet to about 1200yds, then the 350gr 338cal bullet will take over for balistics and retained energy. Make no mistake, the 300mk has made numerous Elk kills past 1800yds. From the desk of a rifle builder, no expert on exterior balistics! [/QUOTE]
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