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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Anyone own a 7mm 300 Win Mag?
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<blockquote data-quote="Kiwi Nate" data-source="post: 904864" data-attributes="member: 8533"><p>If running a fixed lead reamer in the 7mm Practical, a good versatile bolt face to lead measurement would be 73.08mm or 2.877". This gives max COAL's of around 92mm or 3.622" with the A-Max and 92.2mm or 3.630" with the 190 grain Matrix. But again, it is important to check your magazine length to make sure it can handle cartridges of this length. </p><p></p><p>Putting the above into laymans terms, if approaching PTG or any reamer maker, you can set the throat length for a long magazine rifle (as opposed to the original no throat design) by including the statement: Please include freebore, bolt face to lead is to be 2.877". This comment can be placed during the order process. </p><p></p><p>Freebore is therefore .2043"</p><p></p><p>The .188" freebore is not far off this figure and not really enough to negatively effect velocity potential in a meaningful manner. Individual bore tolerances would have as much effect. So I think PTG have done OK with this estimate for Cockroft.</p><p></p><p>And as a final reminder, less freebore should be employed if for example, employing a Howa action which is right on the limit for minimum magazine length. Either use my no throat design and separate throat reamer or if using a reamer that features lead (what end users call the throat), set the bolt face to lead measurement at 2.836". </p><p></p><p>All of the measurements given here are with regard to allowing the shooter to seat close to the lands. Some folk may wish to adopt a little more bullet jump. For example, it is no great trick to get Berger bullets to shoot with 40 thou or more jump. In fact more often than not, the Berger bullets do much better with increased jump. If we take this a bit further and look the reamer Cockroft obtained, max COAL with the 168gr VLD is around 91.6mm or 3.606". The Howa / Vanguard (mag length 91mm or 3.582") feeds smoothly at a COAL of 90.2mm or 3.551" with a resulting bullet jump of 1.4mm or .055. </p><p></p><p>Really hope that makes sense and does not sound like a load of waffle.</p></blockquote><p></p>
[QUOTE="Kiwi Nate, post: 904864, member: 8533"] If running a fixed lead reamer in the 7mm Practical, a good versatile bolt face to lead measurement would be 73.08mm or 2.877". This gives max COAL's of around 92mm or 3.622" with the A-Max and 92.2mm or 3.630" with the 190 grain Matrix. But again, it is important to check your magazine length to make sure it can handle cartridges of this length. Putting the above into laymans terms, if approaching PTG or any reamer maker, you can set the throat length for a long magazine rifle (as opposed to the original no throat design) by including the statement: Please include freebore, bolt face to lead is to be 2.877". This comment can be placed during the order process. Freebore is therefore .2043" The .188" freebore is not far off this figure and not really enough to negatively effect velocity potential in a meaningful manner. Individual bore tolerances would have as much effect. So I think PTG have done OK with this estimate for Cockroft. And as a final reminder, less freebore should be employed if for example, employing a Howa action which is right on the limit for minimum magazine length. Either use my no throat design and separate throat reamer or if using a reamer that features lead (what end users call the throat), set the bolt face to lead measurement at 2.836". All of the measurements given here are with regard to allowing the shooter to seat close to the lands. Some folk may wish to adopt a little more bullet jump. For example, it is no great trick to get Berger bullets to shoot with 40 thou or more jump. In fact more often than not, the Berger bullets do much better with increased jump. If we take this a bit further and look the reamer Cockroft obtained, max COAL with the 168gr VLD is around 91.6mm or 3.606". The Howa / Vanguard (mag length 91mm or 3.582") feeds smoothly at a COAL of 90.2mm or 3.551" with a resulting bullet jump of 1.4mm or .055. Really hope that makes sense and does not sound like a load of waffle. [/QUOTE]
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Anyone own a 7mm 300 Win Mag?
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