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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
338 lapua Build advice sav 110/stevens 200
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<blockquote data-quote="PEI Rob" data-source="post: 278774" data-attributes="member: 3405"><p>The action is 1.355" OD. Lets say the large shank threads penetrate to a max of 1.125". That gives us a .115" thick ring equal to .498" square, say 1/2 an inch to make the math easy. She aint going to stretch because of thrust. The action lugs are being pushed on and the metal is thicker behind the top lug and I'd need VarmitAl to figure out what goes on behind the bottom lug, but I doubt it has anything to do with the shank diameter. You can increase the "size of the abutments" all you want but unless you increase the bolt lug diameter with it, there is no point, the shear forces start at the lugs. Savage increased the shank diameter to increase the amount of "meat" around the chamber and they stopped at the threads. The diameter of the area in front of the action lugs and before the threads remain the same, slightly larger than the bolt head at about 1" and that's about .785" square.</p><p></p><p></p><p>The combined surface area of both lugs in theory is .126" square. Bolt head OD is .990", action ID is .702" which leaves .288" Half that is .144" per lug times the width of .440" equals .063" square, two lugs gives .126" square. In reality considerably less because the bolt heads are tumbled leaving rounded edges and don't forget the action cam surfaces are partially under the bolt lugs. More likely around .100" - .110" square. The bolt handle has nothing to do with lug set back. .585" case/chamber gives a .26878" square area. You say 68kpsi. Thats about 18,277 lbs of thrust on .100" - .110" square area or 166,154 psi - 182,770 psi on the lugs. The Rc of the 41L40 lugs is 36-38 which has a yield strength of 165,000 - 173,000. The brass grips the chamber wall and lowers the effective thrust somewhat, good thing too. </p><p></p><p>Is this the "KRAP" you mentioned?</p><p></p><p>Oh, yes, the action is not as hard as the lugs 32-34Rc and about 147,000 psi - 156,000 psi.</p></blockquote><p></p>
[QUOTE="PEI Rob, post: 278774, member: 3405"] The action is 1.355" OD. Lets say the large shank threads penetrate to a max of 1.125". That gives us a .115" thick ring equal to .498" square, say 1/2 an inch to make the math easy. She aint going to stretch because of thrust. The action lugs are being pushed on and the metal is thicker behind the top lug and I'd need VarmitAl to figure out what goes on behind the bottom lug, but I doubt it has anything to do with the shank diameter. You can increase the "size of the abutments" all you want but unless you increase the bolt lug diameter with it, there is no point, the shear forces start at the lugs. Savage increased the shank diameter to increase the amount of "meat" around the chamber and they stopped at the threads. The diameter of the area in front of the action lugs and before the threads remain the same, slightly larger than the bolt head at about 1" and that's about .785" square. The combined surface area of both lugs in theory is .126" square. Bolt head OD is .990", action ID is .702" which leaves .288" Half that is .144" per lug times the width of .440" equals .063" square, two lugs gives .126" square. In reality considerably less because the bolt heads are tumbled leaving rounded edges and don't forget the action cam surfaces are partially under the bolt lugs. More likely around .100" - .110" square. The bolt handle has nothing to do with lug set back. .585" case/chamber gives a .26878" square area. You say 68kpsi. Thats about 18,277 lbs of thrust on .100" - .110" square area or 166,154 psi - 182,770 psi on the lugs. The Rc of the 41L40 lugs is 36-38 which has a yield strength of 165,000 - 173,000. The brass grips the chamber wall and lowers the effective thrust somewhat, good thing too. Is this the "KRAP" you mentioned? Oh, yes, the action is not as hard as the lugs 32-34Rc and about 147,000 psi - 156,000 psi. [/QUOTE]
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338 lapua Build advice sav 110/stevens 200
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