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Rifles, Reloading, Optics, Equipment
Reloading
Primer pocket truing
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<blockquote data-quote="tim_w" data-source="post: 2646677" data-attributes="member: 11132"><p>My thought on primer pocket truing etc with quality brass... Lapua. Is what is the ref point to indicate off of and how does that effect all other critical areas. </p><p></p><p>All the uniformers ref off the case base. What if the rim thickness varies? </p><p>What is the measurement for rim thickness? </p><p>Then what is the measurement from pocket bottom to top and bottom of rim? </p><p>If you indicate off base and find pocket is 0.004 shallow you are now going to remove 0.004 brass from the case head. At the same time reducing the flash hole depth by that same amount. </p><p>What if you had ref off the top of rim and found it was consistent with other cases? </p><p>Now would we need to measure case head thickness at the flash hole to see if that was consistent? </p><p>If you can measure depth of primer pocket and have a seater that is depth adj 0.001 and or seat by feel then pocket depth should not be a major issue unless it's so out of spec it prevent seating below flush.</p><p></p><p>For me I would rather cull/sort then mess with going thru all that for what amounts to a crap shoot for gain/loss. </p><p></p><p>I never mess with flash holes any more. Can not see how without wallowing at least some of the FHs. I will remove a chad or stuck chip. Otherwise, if I have an issue I can see or measure I cull. Always need cases for foulers and pressure test.</p><p></p><p>I do not want to explain my full reloading procedures and why because it's a bit off topic. But I will say I choose to cull and sort. I focus on maximizing consistency in areas proven to have effects. </p><p></p><p>Neck length (check and run into the preset trimmer everytime). Set gap based on neck growth per firing 0.005-0.003. (I hate giving room for carbon rings.) But there must be enough room for the flow understanding it contracts so you need a 2-3 thou more than measured.</p><p></p><p>Internal neck surface co friction. I have used powdered graphite for decades. Recently been testing hBN.</p><p></p><p>Neck compression force on the bullet. Interference fit measurement is popular and most people use this as a force conversion. It is not. This is especially true when dealing with brass and copper alloys. Virgin brass case neck at -0.002" interference force is different than once fired brass neck. A seated case neck force is less the same day its seated than it is the next day or in a week or two. A piece of brass that has just had displacement/flow is in a state of flux. Its not "settled". There is also a possible supported theory of very mild cold/compression welding or bonding over the long term. Having a low CoF substance barrier between neck and bullet surface prevents that as well as decreasing CoF and increase consistency of release.</p><p></p><p>Powder charge precision and consistency. I use a lab scale that can measure even kernel of ball.</p><p></p><p>Concentricity of neck& bullet to shoulder under 0.002. I admit to trying to get as low as possible but I can not say I see it on target. So chalk that up to precision for precision's sake. I go for under a thou.</p><p></p><p>Consistency of BTO as we have all seen what a few thou in jump/BTO can do to a group in tuning. Key to consistent measuring is a gauge that fits the bullet ogive.</p></blockquote><p></p>
[QUOTE="tim_w, post: 2646677, member: 11132"] My thought on primer pocket truing etc with quality brass... Lapua. Is what is the ref point to indicate off of and how does that effect all other critical areas. All the uniformers ref off the case base. What if the rim thickness varies? What is the measurement for rim thickness? Then what is the measurement from pocket bottom to top and bottom of rim? If you indicate off base and find pocket is 0.004 shallow you are now going to remove 0.004 brass from the case head. At the same time reducing the flash hole depth by that same amount. What if you had ref off the top of rim and found it was consistent with other cases? Now would we need to measure case head thickness at the flash hole to see if that was consistent? If you can measure depth of primer pocket and have a seater that is depth adj 0.001 and or seat by feel then pocket depth should not be a major issue unless it's so out of spec it prevent seating below flush. For me I would rather cull/sort then mess with going thru all that for what amounts to a crap shoot for gain/loss. I never mess with flash holes any more. Can not see how without wallowing at least some of the FHs. I will remove a chad or stuck chip. Otherwise, if I have an issue I can see or measure I cull. Always need cases for foulers and pressure test. I do not want to explain my full reloading procedures and why because it's a bit off topic. But I will say I choose to cull and sort. I focus on maximizing consistency in areas proven to have effects. Neck length (check and run into the preset trimmer everytime). Set gap based on neck growth per firing 0.005-0.003. (I hate giving room for carbon rings.) But there must be enough room for the flow understanding it contracts so you need a 2-3 thou more than measured. Internal neck surface co friction. I have used powdered graphite for decades. Recently been testing hBN. Neck compression force on the bullet. Interference fit measurement is popular and most people use this as a force conversion. It is not. This is especially true when dealing with brass and copper alloys. Virgin brass case neck at -0.002" interference force is different than once fired brass neck. A seated case neck force is less the same day its seated than it is the next day or in a week or two. A piece of brass that has just had displacement/flow is in a state of flux. Its not "settled". There is also a possible supported theory of very mild cold/compression welding or bonding over the long term. Having a low CoF substance barrier between neck and bullet surface prevents that as well as decreasing CoF and increase consistency of release. Powder charge precision and consistency. I use a lab scale that can measure even kernel of ball. Concentricity of neck& bullet to shoulder under 0.002. I admit to trying to get as low as possible but I can not say I see it on target. So chalk that up to precision for precision's sake. I go for under a thou. Consistency of BTO as we have all seen what a few thou in jump/BTO can do to a group in tuning. Key to consistent measuring is a gauge that fits the bullet ogive. [/QUOTE]
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