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Rifles, Reloading, Optics, Equipment
Reloading
Shooting rest while developing loads
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<blockquote data-quote="Mikecr" data-source="post: 498456" data-attributes="member: 1521"><p>Bart & BOSS, I was not speaking in terms of POI, but velocity from cold to hot. So I believe we're on different trails. I should have stayed with POI for this discussion.</p><p></p><p>Bart heated metal expands, while cooler metal does not. Right?</p><p>When You fire into a cold barrel, the metal nearest the bore becomes hotter than surrounding metal. This hotter metal will expand in the direction of least resistance, because it can. That is inward, until the rest of the barrel heats up to allow outward expansion.</p><p>Drill a hole in a plate, heat the edges of the hole(rather than the entire plate), and watch the hole constrict -initially.</p><p>You can see it with pin gauges from shot to shot. You can see it with a chronograph from shot to shot. </p><p></p><p>But none of this directly correlates to POI, as ladder tests often show. Too many other barrel stresses + load timing to predict POI from cold to hot & from one barrel to another.</p><p>I've been lucky with a few barrels that hold cold to hot POI, but most of mine haven't.</p><p>However, they can still be consistent and fine for single shots, demanded with hunting.</p><p>So it's my contention that group shooting, however impressive to some, doesn't really relate to our needs here. </p><p>In fact, it can be counterproductive.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 498456, member: 1521"] Bart & BOSS, I was not speaking in terms of POI, but velocity from cold to hot. So I believe we're on different trails. I should have stayed with POI for this discussion. Bart heated metal expands, while cooler metal does not. Right? When You fire into a cold barrel, the metal nearest the bore becomes hotter than surrounding metal. This hotter metal will expand in the direction of least resistance, because it can. That is inward, until the rest of the barrel heats up to allow outward expansion. Drill a hole in a plate, heat the edges of the hole(rather than the entire plate), and watch the hole constrict -initially. You can see it with pin gauges from shot to shot. You can see it with a chronograph from shot to shot. But none of this directly correlates to POI, as ladder tests often show. Too many other barrel stresses + load timing to predict POI from cold to hot & from one barrel to another. I've been lucky with a few barrels that hold cold to hot POI, but most of mine haven't. However, they can still be consistent and fine for single shots, demanded with hunting. So it's my contention that group shooting, however impressive to some, doesn't really relate to our needs here. In fact, it can be counterproductive. [/QUOTE]
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Reloading
Shooting rest while developing loads
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