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Long Range Hunting & Shooting
Muzzle thread size & muzzle swelling?
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<blockquote data-quote="J E Custom" data-source="post: 1591912" data-attributes="member: 2736"><p>This has been talked about before but should be again.</p><p></p><p>There are many things that can cause a diameter change at the muzzle and this is some of them.</p><p></p><p>1 = insufficient barrel wall thickness.</p><p>2 = Improper thread fit between the brake and the barrel tenon. </p><p>In my research on minimum wall thickness to manage the pressure at the muzzle, all barrel makers recommended no less than .137 Thousandths + and not being able to rely on thread fit to help. we went to .150 thousandths minimum muzzle wall thickness. </p><p></p><p>The difference in rifling methods realy make no difference but in reality cut rifle barrels are stress relieved once. buttoned rifled barrels are stressed relieved twice because of the stress inputted during buttoning. so the odds are slightly better that the stress relieve is more consistent with buttoned barrels. but being in the different barrel makers hands we chose not to count on ether method for for the pressure calculations and the best stress relieve for strength.</p><p></p><p>I always recommend the biggest thread diameter possible, but the minimum wall should never be less that the required thickness. different thread pitches of the same size will add some thickness. If a finer thread is used. (A 32 TPI will have a larger minor diameter that a 24 TPI for the same size thread diameter. but if you calculate the </p><p>bore diameter + .150 wall (.300 thousandths total) Example: .308 +</p><p>.300 = .608 diameter and as long as the minor diameter of the Thread chosen exceeds this diameter and good threads are cut,you will be good to go.</p><p></p><p>I have included a link to my web site in the FAQs section that will aid in the selection of thread size minimum, based on barrel size and bore size. (it is in the seventh question)</p><p></p><p><a href="http://www.jecustom.com/index.php?pg=Home&cmd=Cell&cell=FAQ" target="_blank">http://www.jecustom.com/index.php?pg=Home&cmd=Cell&cell=FAQ</a></p><p></p><p>For many years the military has used 1/2"x 28 TPI on 556 to .308</p><p>in our "opinion" and based on barrel makers recommendations the 1/2 x 28 TPI does not meet the requirements of anything with a bore diameter over.257 and should be avoided if possible. </p><p></p><p>So to sum it up. take your bore diameter, add .300 to that and if the TPI doesn't infringe on the minimum thickness and you barrel diameter is over the recommended minimum by .050 then subtract the minor diameter of the thread wanted .</p><p></p><p>J E CUSTOM</p></blockquote><p></p>
[QUOTE="J E Custom, post: 1591912, member: 2736"] This has been talked about before but should be again. There are many things that can cause a diameter change at the muzzle and this is some of them. 1 = insufficient barrel wall thickness. 2 = Improper thread fit between the brake and the barrel tenon. In my research on minimum wall thickness to manage the pressure at the muzzle, all barrel makers recommended no less than .137 Thousandths + and not being able to rely on thread fit to help. we went to .150 thousandths minimum muzzle wall thickness. The difference in rifling methods realy make no difference but in reality cut rifle barrels are stress relieved once. buttoned rifled barrels are stressed relieved twice because of the stress inputted during buttoning. so the odds are slightly better that the stress relieve is more consistent with buttoned barrels. but being in the different barrel makers hands we chose not to count on ether method for for the pressure calculations and the best stress relieve for strength. I always recommend the biggest thread diameter possible, but the minimum wall should never be less that the required thickness. different thread pitches of the same size will add some thickness. If a finer thread is used. (A 32 TPI will have a larger minor diameter that a 24 TPI for the same size thread diameter. but if you calculate the bore diameter + .150 wall (.300 thousandths total) Example: .308 + .300 = .608 diameter and as long as the minor diameter of the Thread chosen exceeds this diameter and good threads are cut,you will be good to go. I have included a link to my web site in the FAQs section that will aid in the selection of thread size minimum, based on barrel size and bore size. (it is in the seventh question) [URL]http://www.jecustom.com/index.php?pg=Home&cmd=Cell&cell=FAQ[/URL] For many years the military has used 1/2"x 28 TPI on 556 to .308 in our "opinion" and based on barrel makers recommendations the 1/2 x 28 TPI does not meet the requirements of anything with a bore diameter over.257 and should be avoided if possible. So to sum it up. take your bore diameter, add .300 to that and if the TPI doesn't infringe on the minimum thickness and you barrel diameter is over the recommended minimum by .050 then subtract the minor diameter of the thread wanted . J E CUSTOM [/QUOTE]
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Muzzle thread size & muzzle swelling?
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