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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Cold Barrel Shots
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<blockquote data-quote="Mikecr" data-source="post: 2293358" data-attributes="member: 1521"><p>I would attest to lighting changes to POI Barrelnut. It's a real phenomenon.</p><p>But Teri is not actually talking about cold bore ACCURACY. </p><p>She's describing PRECISION from 1st shot through the last in long shot strings.</p><p></p><p>On precision,,</p><p>There are probably factory guns without contact bedding and barrel clearance, but nobody would compete with that.</p><p>Obermeyer barrels are cut rifled, and I'm sure this low stress condition is vital to reduce bore wonderings and dimensional changes.</p><p>So where I choose, I choose cut rifled barrels. Some button rifled barrels available go through a cryogenic stress relieving before final lapping. Should do well.</p><p>If I were a competitor with a focus on grouping I would use LabRadar and carefully define MV from each shot in needed strings.</p><p>With this, I would compensate my loads in order, and not just in MV but to bring each back into mark.</p><p>The assumption here being that <u>maybe</u> the bore is changing in dimension and friction, the barrel's elasticity is less than linear, and the powder burn rate is changing with temperature of it's confinement. I would probably experiment with custom fluting to pull barrel droop favorably with increasing temps.</p><p>I don't know of anything else that could be done other than dry pre-fouling to keep the first few with the rest.</p><p></p><p>For cold bore accuracy,,</p><p>The gun still needs to be built well, but I haven't seen barrel attributes causing significant difference.</p><p>This is because accuracy is defined with EACH single shot.</p><p>So I've had bad grouping potential from very accurate guns, and bad accuracy potential from great grouping guns.</p><p>My focus has always been on cold-clean bore accuracy, so the guns providing this are the guns I keep.</p><p>That has always taken cold bore load development to reach though (a lot of work).</p></blockquote><p></p>
[QUOTE="Mikecr, post: 2293358, member: 1521"] I would attest to lighting changes to POI Barrelnut. It's a real phenomenon. But Teri is not actually talking about cold bore ACCURACY. She's describing PRECISION from 1st shot through the last in long shot strings. On precision,, There are probably factory guns without contact bedding and barrel clearance, but nobody would compete with that. Obermeyer barrels are cut rifled, and I'm sure this low stress condition is vital to reduce bore wonderings and dimensional changes. So where I choose, I choose cut rifled barrels. Some button rifled barrels available go through a cryogenic stress relieving before final lapping. Should do well. If I were a competitor with a focus on grouping I would use LabRadar and carefully define MV from each shot in needed strings. With this, I would compensate my loads in order, and not just in MV but to bring each back into mark. The assumption here being that [U]maybe[/U] the bore is changing in dimension and friction, the barrel's elasticity is less than linear, and the powder burn rate is changing with temperature of it's confinement. I would probably experiment with custom fluting to pull barrel droop favorably with increasing temps. I don't know of anything else that could be done other than dry pre-fouling to keep the first few with the rest. For cold bore accuracy,, The gun still needs to be built well, but I haven't seen barrel attributes causing significant difference. This is because accuracy is defined with EACH single shot. So I've had bad grouping potential from very accurate guns, and bad accuracy potential from great grouping guns. My focus has always been on cold-clean bore accuracy, so the guns providing this are the guns I keep. That has always taken cold bore load development to reach though (a lot of work). [/QUOTE]
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