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Long Range Hunting & Shooting
30 Nosler & 300 PRC vs 30-28 Nosler & 300 PRC SI Wildcats
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<blockquote data-quote="BoatTail" data-source="post: 1562259" data-attributes="member: 74670"><p>In order to consider one of these four cartridges for a custom long-range rifle build, I need to consider the neck, throat and freebore of the chamber. My goal is to select or request a case and reamer that promotes small velocity standard deviations (SD) standard deviations and limited extreme spreads (ED). It also needs to limit the bullet incursion into the case, to maximize powder volume while fitting in the magazine.</p><p></p><p>Here are the reamer, neck, throat and freebore dimensions of two of our focused cartridges.</p><p></p><p>[ATTACH=full]120149[/ATTACH] </p><p>Of the two, we are told that the 300 PRC was designed to have a custom chamber and that the case was designed at the same time. While I'm not an expert, lets see if we can validate which might be better. It will help me decide what to end up with.</p><p></p><p>The SAAMI version of the 30 Nosler has a neck of 0.346. I've been taught you need a minimum of 0.003 clearance on the neck of the loaded round to the chamber. Too much clearance and I found I get larger SD's, inconsistent velocities and the alignment to the throat and then to the rifling is challenged which affects accuracy.</p><p></p><p>[ATTACH=full]120152[/ATTACH]</p><p><strong></strong></p><p><strong>30 Nosler -</strong> The new Nosler case necks I measured varied between 0.0156 and 0.0162. Without turning the necks for consistency, this means there is between a 0.0023 to 0.0013 extra gap. This is an example of too much slop in the neck</p><p></p><p><strong>300 PRC – </strong>I don't have any 300 PRC cases to check neck thickness. I thought I read where someone provided the thickness on new brass. Without it, what I believe is as Hornady said, they designed the case and the chamber at the same time so it makes sense that the 300 PRC case neck thickness has a tighter tolerance and that the average is likely slightly smaller but no greater than 0.0155. This would then limit the slop when the bullet leaves the case and provide better alignment to the throat and into the rifling.</p><p></p><p>I'll stop her and we can discuss throat size advantages next time.</p></blockquote><p></p>
[QUOTE="BoatTail, post: 1562259, member: 74670"] In order to consider one of these four cartridges for a custom long-range rifle build, I need to consider the neck, throat and freebore of the chamber. My goal is to select or request a case and reamer that promotes small velocity standard deviations (SD) standard deviations and limited extreme spreads (ED). It also needs to limit the bullet incursion into the case, to maximize powder volume while fitting in the magazine. Here are the reamer, neck, throat and freebore dimensions of two of our focused cartridges. [ATTACH=full]120149[/ATTACH] Of the two, we are told that the 300 PRC was designed to have a custom chamber and that the case was designed at the same time. While I’m not an expert, lets see if we can validate which might be better. It will help me decide what to end up with. The SAAMI version of the 30 Nosler has a neck of 0.346. I’ve been taught you need a minimum of 0.003 clearance on the neck of the loaded round to the chamber. Too much clearance and I found I get larger SD’s, inconsistent velocities and the alignment to the throat and then to the rifling is challenged which affects accuracy. [ATTACH=full]120152[/ATTACH] [B] 30 Nosler -[/B] The new Nosler case necks I measured varied between 0.0156 and 0.0162. Without turning the necks for consistency, this means there is between a 0.0023 to 0.0013 extra gap. This is an example of too much slop in the neck [B]300 PRC – [/B]I don’t have any 300 PRC cases to check neck thickness. I thought I read where someone provided the thickness on new brass. Without it, what I believe is as Hornady said, they designed the case and the chamber at the same time so it makes sense that the 300 PRC case neck thickness has a tighter tolerance and that the average is likely slightly smaller but no greater than 0.0155. This would then limit the slop when the bullet leaves the case and provide better alignment to the throat and into the rifling. I’ll stop her and we can discuss throat size advantages next time. [/QUOTE]
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30 Nosler & 300 PRC vs 30-28 Nosler & 300 PRC SI Wildcats
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