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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
7mm SAUM Wildcat!
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<blockquote data-quote="calinb" data-source="post: 622484" data-attributes="member: 31242"><p>I did some case capacity calculations and Quickload runs on several candidate parent cases and I think I may have found a simple wildcat solution to my problem (feeding 7mm 180 gr Berger VLDs from a short action mag).</p><p></p><p>The 7mm WSM seems to be the least case capacity-challenged of the short action 7mm cartridge bunch (by a very slight margin) so it would be simple to just push back the 7mm WSM shoulder by 0.100" and get some COAL breathing room. I'll call it the 7mm WSM LRMF (long-range mag-fed). I think the chamber free bore and throat probably need appropriate adjustments too, to make sure the VLDs can touch the lands.</p><p></p><p>My goal is 2950 fps from a 28" barrel. Here are the Quickload results of pushing the 7mm WSM shoulder back 0.010" using readily available powders:</p><p></p><p>Cartridge : 7 mm WSMLRMF</p><p>Bullet : .284, 180, Berger M T VLD G7 #28502</p><p>Useable Case Capaci: 67.267 grain H2O = 4.368 cm³</p><p>Cartridge O.A.L. L6: 2.980 inch = 75.69 mm</p><p>Barrel Length : 28.0 inch = 711.2 mm</p><p></p><p>Ramshot Magnum (Big Boy)-------------102.2 3035</p><p>Vihtavuori N560----------------------------99.8 3033</p><p>Accurate MAGPRO-------------------------100.1 3030</p><p>IMR 7828----------------------------------104.3 3019</p><p>IMR 7828 SSC------------------------------98.6 3019</p><p>Alliant Reloder-22-------------------------100.1 3000</p><p>Winchester WXR--------------------------102.8 3000</p><p>Alliant Reloder-25-------------------------105.0 2997</p><p>Vihtavuori N570---------------------------105.0 2988</p><p>Alliant Reloder-19---------------------------97.2 2957</p><p></p><p>Pushing the neck back 0.100" costs 5.9 gr. H20 but 0.9 gr. H20 could optionally be "recovered" by reducing the case taper to 0.010" (or "spend" the taper reduction to push the shoulder back another 0.030).</p><p></p><p>From my experience, just pushing a short magnum case neck back 0.100" is a fairly easy task in forming new brass, though it's about the limit of what I've attempted to do. </p><p></p><p>A wildcat seems like a lot of trouble for only 0.100" or 0.130" of COAL relief, but I think my goal is marginal without it. Unless extraction problems are anticipated, it seems like the additional 0.030" COAL increase from trading off the cartridge taper is worthwhile. Every little bit helps in this application.</p><p></p><p>In fact, I'd rather have 0.150" to 0.200" of COAL "guardband," which may be possible with a further reduction in case capacity. Quickload seems to be a touch pessimistic with many of these long range 7mm loads and I was limiting QL to only SAMMI max. pressure. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink ;)" loading="lazy" data-shortname=";)" /> </p><p></p><p>So maybe I can rework the Ruger M77 308 Win bolt face and extractor and use the Ruger GSR as a platform after all.</p><p></p><p>Comments, suggestions, or ideas?</p><p></p><p>Thanks,</p><p></p><p>-Cal</p></blockquote><p></p>
[QUOTE="calinb, post: 622484, member: 31242"] I did some case capacity calculations and Quickload runs on several candidate parent cases and I think I may have found a simple wildcat solution to my problem (feeding 7mm 180 gr Berger VLDs from a short action mag). The 7mm WSM seems to be the least case capacity-challenged of the short action 7mm cartridge bunch (by a very slight margin) so it would be simple to just push back the 7mm WSM shoulder by 0.100" and get some COAL breathing room. I'll call it the 7mm WSM LRMF (long-range mag-fed). I think the chamber free bore and throat probably need appropriate adjustments too, to make sure the VLDs can touch the lands. My goal is 2950 fps from a 28" barrel. Here are the Quickload results of pushing the 7mm WSM shoulder back 0.010" using readily available powders: Cartridge : 7 mm WSMLRMF Bullet : .284, 180, Berger M T VLD G7 #28502 Useable Case Capaci: 67.267 grain H2O = 4.368 cm³ Cartridge O.A.L. L6: 2.980 inch = 75.69 mm Barrel Length : 28.0 inch = 711.2 mm Ramshot Magnum (Big Boy)-------------102.2 3035 Vihtavuori N560----------------------------99.8 3033 Accurate MAGPRO-------------------------100.1 3030 IMR 7828----------------------------------104.3 3019 IMR 7828 SSC------------------------------98.6 3019 Alliant Reloder-22-------------------------100.1 3000 Winchester WXR--------------------------102.8 3000 Alliant Reloder-25-------------------------105.0 2997 Vihtavuori N570---------------------------105.0 2988 Alliant Reloder-19---------------------------97.2 2957 Pushing the neck back 0.100" costs 5.9 gr. H20 but 0.9 gr. H20 could optionally be "recovered" by reducing the case taper to 0.010" (or "spend" the taper reduction to push the shoulder back another 0.030). From my experience, just pushing a short magnum case neck back 0.100" is a fairly easy task in forming new brass, though it's about the limit of what I've attempted to do. A wildcat seems like a lot of trouble for only 0.100" or 0.130" of COAL relief, but I think my goal is marginal without it. Unless extraction problems are anticipated, it seems like the additional 0.030" COAL increase from trading off the cartridge taper is worthwhile. Every little bit helps in this application. In fact, I'd rather have 0.150" to 0.200" of COAL "guardband," which may be possible with a further reduction in case capacity. Quickload seems to be a touch pessimistic with many of these long range 7mm loads and I was limiting QL to only SAMMI max. pressure. ;) So maybe I can rework the Ruger M77 308 Win bolt face and extractor and use the Ruger GSR as a platform after all. Comments, suggestions, or ideas? Thanks, -Cal [/QUOTE]
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