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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Will very high polished finish on brass cause Excessive stress on bolt face?
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<blockquote data-quote="T3-OleMan" data-source="post: 487237" data-attributes="member: 14600"><p><span style="color: #000000">......."[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">the principal stresses in this brass ring-element are not necessarily the same functions of chamber pressure </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>P(t) </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">as they were previously when we were looking at a ring-element of the case neck. The </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>radial </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">and </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>tangential </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">stresses can be parameterized just as before: </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Sr = -P(t), </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">and </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>St = 2k P(t). </strong></span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">However, the </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>axial </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">(z-direction) stress </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Sz </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">in the case walls must be </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>reduced </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">because of the presence of the primer cup acting as a smaller, secondary piston within the case head and acting separately against the bolt face. This primer force itself </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>does not </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">contribute to the stretching of the case walls back toward the bolt face, but the force of friction between the primer cup and the walls of its pocket </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em><strong>resists any relative motion</strong></em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, including the "pushing out" of the primer cup against the bolt face while the case head is being "held back" by the larger "wall stretching" forces. This primer friction force is </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>dragging forward on the case head</em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, and so it </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>does </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">contribute additively to case wall stretching. </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Looking only at the </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>peak forces </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">occurring at the maximum chamber pressure </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Pm = 57,400 psi</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, let us define the </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>fraction </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">of the total peak force on the case head </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Ft(Pm) </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">that is available to </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>stretch the side walls of the case </em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">to be another ratio </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>b</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, such that: </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>b = [Ft(Pm) – Fppr(Pm) + Ffpr(Pm)] / Ft(Pm) = 0.8010 </strong></span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">where </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Ft(Pm) </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">= Total peak rearward force on case head assembly </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>= Pm (π/4) D</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 9px"><strong>2 </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>= 6282 pounds </strong></span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Fppr(Pm) = </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Peak potential primer force on bolt face </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>= Pm (π/4) d</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 9px"><strong>2 </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>= 1988 pounds</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, and </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Ffpr(Pm) = </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Peak primer sidewall friction force in the primer pocket </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>= (Cf) (Pm) (Apw) = 738 pounds. </strong></span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">where </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>d = 0.210 inch</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, the outside diameter of a "large rifle" primer cup, and </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>Cf = 0.30 = </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Coefficient of friction used in the FEA for the primer cup in the primer pocket of the case head</span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>. </strong></span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Here, we are using the </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em>adjusted value</em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>D = 0.3733 inch</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">, for the </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><em><strong>effective piston diameter </strong></em></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">inside the case head of our example .308 Winchester cartridge. This value was derived from the proportional relationship between the two effective piston areas involved (and thence the squares of their diameters) and their peak bolt thrust forces at peak chamber pressure: </span>[/FONT]</span></p><p><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>D = d [Ft / Fppr]</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 9px"><strong>1/2 </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>= d [(Fb + Fz) / (Fpr + Ffpr)]</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 9px"><strong>1/2 </strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">≈ </span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>d [Fb / Fpr]</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 9px"><strong>1/2</strong></span>[/FONT]</span><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px"><strong>. "<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite6" alt=":cool:" title="Cool :cool:" loading="lazy" data-shortname=":cool:" /></strong></span>[/FONT]</span></p><p> </p><p> </p><p><strong><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Wood, you nailed it with that link. Thanks</span>[/FONT]</span></strong></p><p><strong><span style="color: #000000">[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">That's just what I said in my own redneck way-LOL!</span>[/FONT]</span></strong></p><p><span style="color: #000000">lightbulb"<strong>[FONT=Times New Roman, Times New Roman, serif]<span style="font-size: 12px">Seems logical that when ignition occurs the brass is slammed against the walls of the chamber and then is rammed back against bolt face more than normal cause the brass can't get a grip on the walls of chamber cause it's to slick!" I rest my case!!!!</span>[/FONT]</strong></span></p><p> </p><p><strong><span style="font-family: 'Times New Roman'"><span style="font-size: 12px">Thus I am getting extractor marks???? Are they real dangerous if not deep, and only ocassional?</span></span></strong></p></blockquote><p></p>
[QUOTE="T3-OleMan, post: 487237, member: 14600"] [COLOR=#000000].......“[FONT=Times New Roman, Times New Roman, serif][SIZE=3]the principal stresses in this brass ring-element are not necessarily the same functions of chamber pressure [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]P(t) [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]as they were previously when we were looking at a ring-element of the case neck. The [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]radial [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]and [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]tangential [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]stresses can be parameterized just as before: [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Sr = -P(t), [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]and [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]St = 2k P(t). [/B][/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]However, the [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]axial [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3](z-direction) stress [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Sz [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]in the case walls must be [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]reduced [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]because of the presence of the primer cup acting as a smaller, secondary piston within the case head and acting separately against the bolt face. This primer force itself [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]does not [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]contribute to the stretching of the case walls back toward the bolt face, but the force of friction between the primer cup and the walls of its pocket [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I][B]resists any relative motion[/B][/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], including the “pushing out” of the primer cup against the bolt face while the case head is being “held back” by the larger “wall stretching” forces. This primer friction force is [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]dragging forward on the case head[/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], and so it [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]does [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]contribute additively to case wall stretching. [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Looking only at the [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]peak forces [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]occurring at the maximum chamber pressure [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Pm = 57,400 psi[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], let us define the [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]fraction [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]of the total peak force on the case head [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Ft(Pm) [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]that is available to [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]stretch the side walls of the case [/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]to be another ratio [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]b[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], such that: [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]b = [Ft(Pm) – Fppr(Pm) + Ffpr(Pm)] / Ft(Pm) = 0.8010 [/B][/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]where [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Ft(Pm) [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]= Total peak rearward force on case head assembly [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]= Pm (π/4) D[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=1][B]2 [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]= 6282 pounds [/B][/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Fppr(Pm) = [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Peak potential primer force on bolt face [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]= Pm (π/4) d[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=1][B]2 [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]= 1988 pounds[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], and [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Ffpr(Pm) = [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Peak primer sidewall friction force in the primer pocket [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]= (Cf) (Pm) (Apw) = 738 pounds. [/B][/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]where [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]d = 0.210 inch[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], the outside diameter of a “large rifle” primer cup, and [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]Cf = 0.30 = [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Coefficient of friction used in the FEA for the primer cup in the primer pocket of the case head[/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]. [/B][/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Here, we are using the [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I]adjusted value[/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]D = 0.3733 inch[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3], for the [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][I][B]effective piston diameter [/B][/I][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]inside the case head of our example .308 Winchester cartridge. This value was derived from the proportional relationship between the two effective piston areas involved (and thence the squares of their diameters) and their peak bolt thrust forces at peak chamber pressure: [/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]D = d [Ft / Fppr][/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=1][B]1/2 [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]= d [(Fb + Fz) / (Fpr + Ffpr)][/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=1][B]1/2 [/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]≈ [/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]d [Fb / Fpr][/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=1][B]1/2[/B][/SIZE][/FONT][/COLOR][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3][B]. “:cool:[/B][/SIZE][/FONT][/COLOR] [B][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Wood, you nailed it with that link. Thanks[/SIZE][/FONT][/COLOR][/B] [B][COLOR=#000000][FONT=Times New Roman, Times New Roman, serif][SIZE=3]That's just what I said in my own redneck way-LOL![/SIZE][/FONT][/COLOR][/B] [COLOR=#000000]lightbulb“[B][FONT=Times New Roman, Times New Roman, serif][SIZE=3]Seems logical that when ignition occurs the brass is slammed against the walls of the chamber and then is rammed back against bolt face more than normal cause the brass can't get a grip on the walls of chamber cause it's to slick!” I rest my case!!!![/SIZE][/FONT][/B][/COLOR] [B][FONT=Times New Roman][SIZE=3]Thus I am getting extractor marks???? Are they real dangerous if not deep, and only ocassional?[/SIZE][/FONT][/B] [/QUOTE]
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Will very high polished finish on brass cause Excessive stress on bolt face?
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