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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Using Quick Load for Optimum Barrel Timing and OCW Node Matches
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<blockquote data-quote="Oak_Leaf" data-source="post: 3001081" data-attributes="member: 128477"><p>I'm gonna just go ahead and say this because I see people making incorrect references to the different theories of harmonics and OBT all the time. Chris Long's OBT theory, and the harmonic bending modes are not the same thing.</p><p></p><p>The bending modes (harmonics) determine which way the barrel is pointed at a given time, and we use this to positively compensate our MV spreads over a charge range, at a specified distance. Chris Long's theory has to do with the wave that repeatedly expands and contracts the bore. These are two totally different beasts. Chris's theory really has to do with group size variations, in general, and has nothing to do with positive compensation that happens to the bending modes.</p><p></p><p>When you're looking at barrel times in QL, you will have both a bending mode (harmonic) AND a bore size change BOTH affecting the rifle - and each one could be favorable or unfavorable at that barrel time. For example, here's a common scenario ... say QL was accurate, and you found a load that 100% matched up to the Chris's OBT, you could also be at a <u>unfavorable</u> spot in the bending cycle. That load might shoot tiny groups, but poi would be sensitive to MV changes, like temperature or powder charge variations. A load like this, I believe, would be referred to by most shooters as "not in a node".</p><p></p><p>When people find their "node" - via OCW, ladder - what they've found is a sweet spot on the bending cycle that allows for good positive compensation over their MV spreads over that charge range. But, because of the way positive compensation works, it only compensates at that specific distance you worked up your load at - and you may or may not be at an OBT. In other words, a "node", as most of us refer to from the OCW or ladder test, is not very sensitive to MV changes and works well across temp changes, etc., but it may not give the tiniest groups because it may be not aligned with an optimum barrel time.</p><p></p><p>These two phenomenon are talked about all the time as if they are the same thing, and they are most definitely not. But, it makes for good long thread, lol.</p><p></p><p>ETA - but if you can find a recipe (rifle, powder, bullet, etc) where the bending modes AND the OBT are both favorable, and you have low MV spreads to top it off, then you got a real shooter. I believe a lot of the competition guys doing the high precision and ELR shooting have these recipes figured out.</p></blockquote><p></p>
[QUOTE="Oak_Leaf, post: 3001081, member: 128477"] I'm gonna just go ahead and say this because I see people making incorrect references to the different theories of harmonics and OBT all the time. Chris Long's OBT theory, and the harmonic bending modes are not the same thing. The bending modes (harmonics) determine which way the barrel is pointed at a given time, and we use this to positively compensate our MV spreads over a charge range, at a specified distance. Chris Long's theory has to do with the wave that repeatedly expands and contracts the bore. These are two totally different beasts. Chris's theory really has to do with group size variations, in general, and has nothing to do with positive compensation that happens to the bending modes. When you're looking at barrel times in QL, you will have both a bending mode (harmonic) AND a bore size change BOTH affecting the rifle - and each one could be favorable or unfavorable at that barrel time. For example, here's a common scenario ... say QL was accurate, and you found a load that 100% matched up to the Chris's OBT, you could also be at a [U]unfavorable[/U] spot in the bending cycle. That load might shoot tiny groups, but poi would be sensitive to MV changes, like temperature or powder charge variations. A load like this, I believe, would be referred to by most shooters as "not in a node". When people find their "node" - via OCW, ladder - what they've found is a sweet spot on the bending cycle that allows for good positive compensation over their MV spreads over that charge range. But, because of the way positive compensation works, it only compensates at that specific distance you worked up your load at - and you may or may not be at an OBT. In other words, a "node", as most of us refer to from the OCW or ladder test, is not very sensitive to MV changes and works well across temp changes, etc., but it may not give the tiniest groups because it may be not aligned with an optimum barrel time. These two phenomenon are talked about all the time as if they are the same thing, and they are most definitely not. But, it makes for good long thread, lol. ETA - but if you can find a recipe (rifle, powder, bullet, etc) where the bending modes AND the OBT are both favorable, and you have low MV spreads to top it off, then you got a real shooter. I believe a lot of the competition guys doing the high precision and ELR shooting have these recipes figured out. [/QUOTE]
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