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Rifles, Reloading, Optics, Equipment
Gunsmithing
When checking bolt-lug face surface % with a sharpie...
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<blockquote data-quote="J E Custom" data-source="post: 1643782" data-attributes="member: 2736"><p>I will try to answer best I can.</p><p></p><p>First, like everything else a poor job, be it lapping or machining will cause many other problems that otherwise would not exist so I lap after the machining is done on the recoil surfaces to reduce the resistance to lift the bolt after firing , because as you know We tend to load very heavy and bolt lift can be difficult. Bench rest folks normally don't load hard so this is not a problem for them.Also even the machined surface is not as smooth as it can be with lapping.</p><p></p><p>And yes the trigger/cocking piece, does apply upward force to the bolt and it tends to ride on the top of the bolt while cocked. with a preferred tolerance between the bolt and the raceway of .001 to .003 this allows the bolt to rise off center by .0005 to .0015 (Not very much misalignment). but upon firing, the bolt will seek true center and this is where I want it to be and have machined and trued for. The bolt cant misalign the case head permanently but 55,000 to 65,000 psi can.</p><p></p><p>Reaching these pressures takes Milliseconds and the bolt will be forced into what ever alignment it allows. This is also the reason we machine the lugs and the abutments square to the bore center line. If you have .0000 head space this phenomena is not encountered because the bolt will be self aligned by compression. most smiths prefer head space of .0005 to .0015 for accuracy and .001 to .004 for function. in these cases the cocking piece will thrust the bolt upward and remove the clearance on top until the sear releases the cocking piece. </p><p></p><p>I was trained by a Bench rest shooter/builder and many of his philosophies carry over to our sport but not all, because of different requirements between the two sports.</p><p></p><p>I hope this explained why I do things the way I do. Others disagree with some of these philosophizes and that's fine This works best for me.</p><p></p><p>PS: Don't worry about challenging or questing something I do, Because I don;t know everything about anything, and can learn something if I am lucky. I only post what works for me.</p><p></p><p>J E CUSTOM</p></blockquote><p></p>
[QUOTE="J E Custom, post: 1643782, member: 2736"] I will try to answer best I can. First, like everything else a poor job, be it lapping or machining will cause many other problems that otherwise would not exist so I lap after the machining is done on the recoil surfaces to reduce the resistance to lift the bolt after firing , because as you know We tend to load very heavy and bolt lift can be difficult. Bench rest folks normally don't load hard so this is not a problem for them.Also even the machined surface is not as smooth as it can be with lapping. And yes the trigger/cocking piece, does apply upward force to the bolt and it tends to ride on the top of the bolt while cocked. with a preferred tolerance between the bolt and the raceway of .001 to .003 this allows the bolt to rise off center by .0005 to .0015 (Not very much misalignment). but upon firing, the bolt will seek true center and this is where I want it to be and have machined and trued for. The bolt cant misalign the case head permanently but 55,000 to 65,000 psi can. Reaching these pressures takes Milliseconds and the bolt will be forced into what ever alignment it allows. This is also the reason we machine the lugs and the abutments square to the bore center line. If you have .0000 head space this phenomena is not encountered because the bolt will be self aligned by compression. most smiths prefer head space of .0005 to .0015 for accuracy and .001 to .004 for function. in these cases the cocking piece will thrust the bolt upward and remove the clearance on top until the sear releases the cocking piece. I was trained by a Bench rest shooter/builder and many of his philosophies carry over to our sport but not all, because of different requirements between the two sports. I hope this explained why I do things the way I do. Others disagree with some of these philosophizes and that's fine This works best for me. PS: Don't worry about challenging or questing something I do, Because I don;t know everything about anything, and can learn something if I am lucky. I only post what works for me. J E CUSTOM [/QUOTE]
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When checking bolt-lug face surface % with a sharpie...
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