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Rifles, Reloading, Optics, Equipment
Reloading
Concentricity:How much ?
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<blockquote data-quote="Bart B" data-source="post: 362478" data-attributes="member: 5302"><p>I think one thousandths spread in neck wall thickness is fine. There's too many other things that'll open up ones groups at any range to make a difference in cartridges burning more than 40 grains of powder.</p><p></p><p>Nor do I think a "death grip" of extractors hurt accuracy either. The difference in a death grip and none at all will only change the location of the back end of the case a couple thousandths at most. Not enough to make a difference in my opinion. The smallest 15+ shot groups I know of past 300 yards have all been shot with rifles with such force at right angles to the case/chamber axis.</p><p></p><p>Here's some examples of what such neck wall variance and death grip extractors will do at 800 and 1000 yards when bullet runout's no more than 2 thousandths:</p><p></p><p>First, 20 shots from a .308 Win. 30-inch Kreiger barrel in a Paramount 4-lug action using WCC60 unpreped full-length sized cases with a Sierra 155-gr. Palma bullet; number 1 and 2 were the first two shots from a cold barrel after two sighters:</p><p></p><p><img src="http://i735.photobucket.com/albums/ww351/BartBob/20at800-1.jpg?t=1266244712" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Second, my plot from testing a new Kreiger barrel in my Model 70 long range rifle. .30-.338 Keele (.300 Win. Mag. case run through .30-.338 full length sizing die) unprepped cases. Top 15 black dots are impacts from once fired, full length sized cases shooting Sierra 190's. Bottom 15 red dots from new full length sized cases shooting Sierra 200's. All HPMK bullets were shot alternatly, one 190 then one 200; all 30 shots fired about 20 to 25 seconds apart after two sighting shots were fired to zero. That X-ring's 10 inches in diameter. </p><p></p><p><img src="http://i735.photobucket.com/albums/ww351/BartBob/30at1000.jpg?t=1266244670" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>I thought it was interesting that two loads shot so close together.</p></blockquote><p></p>
[QUOTE="Bart B, post: 362478, member: 5302"] I think one thousandths spread in neck wall thickness is fine. There's too many other things that'll open up ones groups at any range to make a difference in cartridges burning more than 40 grains of powder. Nor do I think a "death grip" of extractors hurt accuracy either. The difference in a death grip and none at all will only change the location of the back end of the case a couple thousandths at most. Not enough to make a difference in my opinion. The smallest 15+ shot groups I know of past 300 yards have all been shot with rifles with such force at right angles to the case/chamber axis. Here's some examples of what such neck wall variance and death grip extractors will do at 800 and 1000 yards when bullet runout's no more than 2 thousandths: First, 20 shots from a .308 Win. 30-inch Kreiger barrel in a Paramount 4-lug action using WCC60 unpreped full-length sized cases with a Sierra 155-gr. Palma bullet; number 1 and 2 were the first two shots from a cold barrel after two sighters: [img]http://i735.photobucket.com/albums/ww351/BartBob/20at800-1.jpg?t=1266244712[/img] Second, my plot from testing a new Kreiger barrel in my Model 70 long range rifle. .30-.338 Keele (.300 Win. Mag. case run through .30-.338 full length sizing die) unprepped cases. Top 15 black dots are impacts from once fired, full length sized cases shooting Sierra 190's. Bottom 15 red dots from new full length sized cases shooting Sierra 200's. All HPMK bullets were shot alternatly, one 190 then one 200; all 30 shots fired about 20 to 25 seconds apart after two sighting shots were fired to zero. That X-ring's 10 inches in diameter. [img]http://i735.photobucket.com/albums/ww351/BartBob/30at1000.jpg?t=1266244670[/img] I thought it was interesting that two loads shot so close together. [/QUOTE]
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