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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
JDJones75, 257 STW information...
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<blockquote data-quote="Fiftydriver" data-source="post: 35465" data-attributes="member: 10"><p>Donham,</p><p></p><p>Your last post got me thinking.</p><p></p><p>I have been shooting the 140 gr A-Max in my 6.5-06 AI with 1/2 moa accuracy out to 500 yards.</p><p></p><p>This rifle has a 26.5" barrel with the industry standard 1-9" twist. I was told by some that this twist would not stabilize the 140 gr A-Max but decided to try it anyway.</p><p></p><p>At 3000 fps this bullet very accurate figuring the action I built the rifle on is a Mauser 98 and the first custom accuracy rig I even built.</p><p></p><p>With your comment comparing the 6.5mm with the .257" I realized I had a 500ct box of the grand 155 gr Sierra Mk's on the shelf waiting for my 1-8" 6.5 WSM that I am building for my next XP-100 big game handgun with a 15" barrel.</p><p></p><p>I figured that if the big 155's would stabilize in the 1-9" twist 6.5-06 AI at 2800-2900 fps then I would have a good chance to get the 140 gr RBT ULD bullet to shoot well out of the 257 STW loaded to 3300-3400 fps with a 1-10" twist.</p><p></p><p>I loaded up three loads using H-1000 and the CCI-200 primer. All loads were seated to 3.222" which is 0.005" off the lands and very short for this bullet.</p><p></p><p>The first group averaged 2855 fps and the group at 100 yards measured .945" for three shots CTC. I was not interested in doing a major load developement session, just wanted to see if the bullets would land on point.</p><p></p><p>Obviously they would.</p><p></p><p>The next load up, 56.0 gr cut a .698" ctc three shot group at 2897 fps average.</p><p></p><p>The last group at 57.0 gr suprised me a bit with a ctc group of .326" ctc for three shots and 2935 fps average.</p><p></p><p>Now I am under no impression that this bullet will average this group size but obviously it is stabilized plenty well out of the 1-9" twist.</p><p></p><p>This give me good reason to believe the 140 gr ULD will stabilize in the slightly slower twist but driven to substanially faster velocities.</p><p></p><p>We will have to see.</p><p></p><p>Just thought I would fill you in on the results of this little experiment. I may explore this bullet further in my 6.5-06 AI but think I should lengthen the throat about .250" to get that extremely long bullet out of the case farther. IT take up alot of powder capacity.</p><p></p><p>My 6.5-06 AI reamer was designed for use with the 120 gr Ballsitic Tip and 140 gr Partition, with those bullets to be seated to an oal to allow feeding through a magazine.</p><p></p><p>This is not real good for this very long bullet. I will need to do some serious thinking before I lengthen the throat this much as it may limit what other lighter bullets I can shoot well out of this rifle.</p><p></p><p>GOod Shooting!!!</p><p></p><p>Kirby Allen(50)</p></blockquote><p></p>
[QUOTE="Fiftydriver, post: 35465, member: 10"] Donham, Your last post got me thinking. I have been shooting the 140 gr A-Max in my 6.5-06 AI with 1/2 moa accuracy out to 500 yards. This rifle has a 26.5" barrel with the industry standard 1-9" twist. I was told by some that this twist would not stabilize the 140 gr A-Max but decided to try it anyway. At 3000 fps this bullet very accurate figuring the action I built the rifle on is a Mauser 98 and the first custom accuracy rig I even built. With your comment comparing the 6.5mm with the .257" I realized I had a 500ct box of the grand 155 gr Sierra Mk's on the shelf waiting for my 1-8" 6.5 WSM that I am building for my next XP-100 big game handgun with a 15" barrel. I figured that if the big 155's would stabilize in the 1-9" twist 6.5-06 AI at 2800-2900 fps then I would have a good chance to get the 140 gr RBT ULD bullet to shoot well out of the 257 STW loaded to 3300-3400 fps with a 1-10" twist. I loaded up three loads using H-1000 and the CCI-200 primer. All loads were seated to 3.222" which is 0.005" off the lands and very short for this bullet. The first group averaged 2855 fps and the group at 100 yards measured .945" for three shots CTC. I was not interested in doing a major load developement session, just wanted to see if the bullets would land on point. Obviously they would. The next load up, 56.0 gr cut a .698" ctc three shot group at 2897 fps average. The last group at 57.0 gr suprised me a bit with a ctc group of .326" ctc for three shots and 2935 fps average. Now I am under no impression that this bullet will average this group size but obviously it is stabilized plenty well out of the 1-9" twist. This give me good reason to believe the 140 gr ULD will stabilize in the slightly slower twist but driven to substanially faster velocities. We will have to see. Just thought I would fill you in on the results of this little experiment. I may explore this bullet further in my 6.5-06 AI but think I should lengthen the throat about .250" to get that extremely long bullet out of the case farther. IT take up alot of powder capacity. My 6.5-06 AI reamer was designed for use with the 120 gr Ballsitic Tip and 140 gr Partition, with those bullets to be seated to an oal to allow feeding through a magazine. This is not real good for this very long bullet. I will need to do some serious thinking before I lengthen the throat this much as it may limit what other lighter bullets I can shoot well out of this rifle. GOod Shooting!!! Kirby Allen(50) [/QUOTE]
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