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Rifles, Reloading, Optics, Equipment
Reloading
I seriously doubt this is case head separation but what do you guys think?
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<blockquote data-quote="J E Custom" data-source="post: 1410438" data-attributes="member: 2736"><p>Ok. I will try one more time and then I will stop trying to help you.</p><p></p><p>First lets talk about head space.</p><p>Head space is measured from the Datum line to the bolt face when using shouldered cases.</p><p></p><p>Belted cases are measured from the front of the belt to the bolt face.</p><p></p><p>Rimed cases are measured from the front of the case head to the bolt face.</p><p></p><p>The gauges you use for the 303 (A rimed case) uses gauges that compare head space from the rim thickness (Front of the rim to the bolt face to make the actual head space .064 to .067 plus the normal 1 to 3 thousandths for the actual head space. So if you inserted the .064 gauge and the bolt would just barely close you would have .0000 head space and would be the minimum SAMME chamber head space.</p><p></p><p>If the .067 gauge was used and it would barely allow the bolt to close,</p><p>you would have .003 thousandths head space Not .067 as you posted.</p><p>(The reason I questioned your post for clarification).</p><p></p><p>The use of the .074 gauge is to let you know that the chamber has .010 thousandths head space, not .074 ) and would be to much head space</p><p>and could be dangerous.</p><p></p><p>These gauges only work if the rim thickness is within specified thickness</p><p>that can be added to or taken away from the gauge to end up with the final head space dimension.</p><p></p><p>Head space is whatever clearance exist between the back of the case head and the bolt face with the cartridge pushed forward against which ever part of the chamber the design is used to locate the case. (Front of rim, front of belt, datum line and the front of the case on rimless cases like the 45 Auto and many other rimless cartridges that uses the case mouth to set the head space.</p><p></p><p>On the primer issue. The case is not held in place in the chamber if it is full length sized so it will be the first to move when the powder is ignited. the fact that the case is pushed forward sometimes depending on the chamber fit by the firing pin strike , does not mean that the case stays there until the powder starts to burn forcing the primer to move first. The primer IS pressed in place and does not move before the case does and with the case in full contact with the bolt face, the primer will/cannot move.</p><p></p><p>The only thing that will break the initial primer seal is over pressure loads and this causes bolt face erosion due to high pressure gasses escaping past the primer seal cutting the bolt face. If the primer seal was broken every time A round was fired, the bolt face would not last very long because this seal prevents the gas from channeling through the primer pocket and escaping the cartridge allowing high pressure to cut the bolt face and ruining the case on the first firing.</p><p></p><p>One other thing. In your moving drawing, you are saying that head space is measured from the end of the breach to the bolt face, this is also false. This clearance called bolt clearance and has nothing to do with head space. what you are calling head clearance in your drawing IS actual head space, and where it is measured.</p><p></p><p>Just to be sure I had not misinterpreted you post I went back and carefully read them again and you posted clearly stated that all I had thought you claimed, was there.</p><p></p><p>If this is not clear enough to all, I will make no more attempts to correct your numbers.</p><p></p><p>Sorry If I offended you or anyone else, but these mistakes needed to be discussed/explained so no one would get into trouble.</p><p></p><p>J E CUSTOM</p></blockquote><p></p>
[QUOTE="J E Custom, post: 1410438, member: 2736"] Ok. I will try one more time and then I will stop trying to help you. First lets talk about head space. Head space is measured from the Datum line to the bolt face when using shouldered cases. Belted cases are measured from the front of the belt to the bolt face. Rimed cases are measured from the front of the case head to the bolt face. The gauges you use for the 303 (A rimed case) uses gauges that compare head space from the rim thickness (Front of the rim to the bolt face to make the actual head space .064 to .067 plus the normal 1 to 3 thousandths for the actual head space. So if you inserted the .064 gauge and the bolt would just barely close you would have .0000 head space and would be the minimum SAMME chamber head space. If the .067 gauge was used and it would barely allow the bolt to close, you would have .003 thousandths head space Not .067 as you posted. (The reason I questioned your post for clarification). The use of the .074 gauge is to let you know that the chamber has .010 thousandths head space, not .074 ) and would be to much head space and could be dangerous. These gauges only work if the rim thickness is within specified thickness that can be added to or taken away from the gauge to end up with the final head space dimension. Head space is whatever clearance exist between the back of the case head and the bolt face with the cartridge pushed forward against which ever part of the chamber the design is used to locate the case. (Front of rim, front of belt, datum line and the front of the case on rimless cases like the 45 Auto and many other rimless cartridges that uses the case mouth to set the head space. On the primer issue. The case is not held in place in the chamber if it is full length sized so it will be the first to move when the powder is ignited. the fact that the case is pushed forward sometimes depending on the chamber fit by the firing pin strike , does not mean that the case stays there until the powder starts to burn forcing the primer to move first. The primer IS pressed in place and does not move before the case does and with the case in full contact with the bolt face, the primer will/cannot move. The only thing that will break the initial primer seal is over pressure loads and this causes bolt face erosion due to high pressure gasses escaping past the primer seal cutting the bolt face. If the primer seal was broken every time A round was fired, the bolt face would not last very long because this seal prevents the gas from channeling through the primer pocket and escaping the cartridge allowing high pressure to cut the bolt face and ruining the case on the first firing. One other thing. In your moving drawing, you are saying that head space is measured from the end of the breach to the bolt face, this is also false. This clearance called bolt clearance and has nothing to do with head space. what you are calling head clearance in your drawing IS actual head space, and where it is measured. Just to be sure I had not misinterpreted you post I went back and carefully read them again and you posted clearly stated that all I had thought you claimed, was there. If this is not clear enough to all, I will make no more attempts to correct your numbers. Sorry If I offended you or anyone else, but these mistakes needed to be discussed/explained so no one would get into trouble. J E CUSTOM [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
I seriously doubt this is case head separation but what do you guys think?
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