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Rifles, Reloading, Optics, Equipment
Gunsmithing
Lug setback? What am I missing?
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<blockquote data-quote="cohunt" data-source="post: 1820540" data-attributes="member: 94491"><p>false-- if the lugs were the same size for a .470 bolt head vs a .585 bolt head --lets say that the 2 bolt faces/lugs make up 1 square inch of area-- the .470 bolt head has 10757 pounds pushing on 1 square in so the lugs see 10757 PSI total force (or 5378.5 POUNDS per LUG)-- but the .585 bolt head has 16814 pounds pushing on 1 square inch so the psi on the bolt lugs are now 16814 PSI (or 8407 POUNDS PER LUG)-- the lugs do not see the same PSI as the bolt head does due to the different surface areas-- the chamber pressure is exerted on the bolt face which is transferred to the lugs but due to the differences in face area and lug area the PSI is not the same</p><p></p><p>That is why is is call PSI-- it is pounds per square in exerted NOT pounds-- when you increase the size that the PSI is pushing against, then you increase the actual pounds of force that is exerted</p><p></p><p>maybe think of it like this-- we have a 1000 pound object with a surface area of 10 square inches sitting on the floor===this equals 100 PSI of force on the floor, now take a 1000 pound object with a surface area of 1 square inch sitting on the floor== this same weight object would be exerting 1000 PSI on the floor rather than 100 PSI simply due to its surface area</p><p>--so invert this the other way, use a constant pressure of 1000 PSI not a constant weight--1000 PSI exerted over 10 square inches would be 10000 pounds of pressure-- BUT 1000 PSI exerted over 1 square inch would only be 1000 pounds of force--so in this case the floor would see 10000 pounds vs 1000 pounds of force</p><p>.</p><p>the issue here is people are using 32000 PSI (POUNDS PER SQUARE INCH) and 32000 pounds of force the same way and they are totally different ----even though a 223 runs at 55000 PSI, the bolt face only sees 6800 pounds of force due to the smaller .376" bolt face which would be about .112 square inches -- YET a 308w running at the same 55000 PSI chamber pressure would see about 10500 pounds of force on the bolt face due to the larger surface area of the 308 case</p><p></p><p>PSI is pressure, Pounds (or ft/pounds) is Force -- pressure and force are not the same thing</p><p></p><p>I really dont know how else to explain this so I guess I am out of this thread for now</p></blockquote><p></p>
[QUOTE="cohunt, post: 1820540, member: 94491"] false-- if the lugs were the same size for a .470 bolt head vs a .585 bolt head --lets say that the 2 bolt faces/lugs make up 1 square inch of area-- the .470 bolt head has 10757 pounds pushing on 1 square in so the lugs see 10757 PSI total force (or 5378.5 POUNDS per LUG)-- but the .585 bolt head has 16814 pounds pushing on 1 square inch so the psi on the bolt lugs are now 16814 PSI (or 8407 POUNDS PER LUG)-- the lugs do not see the same PSI as the bolt head does due to the different surface areas-- the chamber pressure is exerted on the bolt face which is transferred to the lugs but due to the differences in face area and lug area the PSI is not the same That is why is is call PSI-- it is pounds per square in exerted NOT pounds-- when you increase the size that the PSI is pushing against, then you increase the actual pounds of force that is exerted maybe think of it like this-- we have a 1000 pound object with a surface area of 10 square inches sitting on the floor===this equals 100 PSI of force on the floor, now take a 1000 pound object with a surface area of 1 square inch sitting on the floor== this same weight object would be exerting 1000 PSI on the floor rather than 100 PSI simply due to its surface area --so invert this the other way, use a constant pressure of 1000 PSI not a constant weight--1000 PSI exerted over 10 square inches would be 10000 pounds of pressure-- BUT 1000 PSI exerted over 1 square inch would only be 1000 pounds of force--so in this case the floor would see 10000 pounds vs 1000 pounds of force . the issue here is people are using 32000 PSI (POUNDS PER SQUARE INCH) and 32000 pounds of force the same way and they are totally different ----even though a 223 runs at 55000 PSI, the bolt face only sees 6800 pounds of force due to the smaller .376" bolt face which would be about .112 square inches -- YET a 308w running at the same 55000 PSI chamber pressure would see about 10500 pounds of force on the bolt face due to the larger surface area of the 308 case PSI is pressure, Pounds (or ft/pounds) is Force -- pressure and force are not the same thing I really dont know how else to explain this so I guess I am out of this thread for now [/QUOTE]
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Lug setback? What am I missing?
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