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Rifles, Reloading, Optics, Equipment
Reloading
Need technical input: rifle project based on 7LRM cartridge necked to .277
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<blockquote data-quote="Magnus777" data-source="post: 2024441" data-attributes="member: 40688"><p>Well, after looking again...seriously looking, with intent to buy some brass, I couldn't find any for immediate sale. Or at least not through normal retailers...didn't check auction sites. No 7 LRM, no 300 PRC. BUT I did discover one retailer with some RWS 6.5x68, which I understand is rather excellent quality brass.</p><p></p><p>Measurements on the 6.5x68mm cartridge are:</p><p></p><table style='width: 100%'><tr><th>Case type</th><td>Rimless, bottleneck</td></tr><tr><th>Bullet diameter</th><td>6.70 mm (0.264 in)</td></tr><tr><th>Neck diameter</th><td>7.60 mm (0.299 in)</td></tr><tr><th>Shoulder diameter</th><td>12.18 mm (0.480 in)</td></tr><tr><th>Base diameter</th><td>13.30 mm (0.524 in)</td></tr><tr><th>Rim diameter</th><td>13.00 mm (0.512 in)</td></tr><tr><th>Rim thickness</th><td>1.40 mm (0.055 in)</td></tr><tr><th>Case length</th><td>67.50 mm (2.657 in)</td></tr><tr><th>Overall length</th><td>86.50 mm (3.406 in)</td></tr><tr><th>Case capacity</th><td>5.58 cm3 (86.1 <a href="https://en.m.wikipedia.org/wiki/Grain_(unit)" target="_blank">gr H2O</a>)</td></tr><tr><th>Rifling twist</th><td>250 mm (1 in 9.84 in)</td></tr><tr><th>Primer type</th><td>Large rifle magnum</td></tr><tr><th>Maximum pressure</th><td>440 MPa (64,000 psi)</td></tr></table><p></p><p>Base diameter is in line with the dimension indicated on the 7 LRM cartridge blueprint. Just saying, since I haven't measured it. Cartridge length of the 7 is 2.514", so this one is .143" longer.</p><p></p><p>But you know...all this right now is just blowing wind! The fact of the matter is, my best choice for brass is unavailable at the moment. Odds are some will turn up by the time it's needed. For right now I have the 100 count of old Hornady brass that can be put to use. It can be sorted, and massaged, and maybe out of the 100 there will be 50 worth farting with, or maybe less. But it will get me that much closer!</p><p>OK, so what's the next step? Order the Hornady bushing dies for 7 LRM? Who's going to have that? Then the reamer, right? It was mentioned that could be done with dummy dummy rounds. Truly? And what about the cartridge blueprint, with adjustments for neck reduction? Will that be necessary?</p></blockquote><p></p>
[QUOTE="Magnus777, post: 2024441, member: 40688"] Well, after looking again...seriously looking, with intent to buy some brass, I couldn't find any for immediate sale. Or at least not through normal retailers...didn't check auction sites. No 7 LRM, no 300 PRC. BUT I did discover one retailer with some RWS 6.5x68, which I understand is rather excellent quality brass. Measurements on the 6.5x68mm cartridge are: [TABLE] [TR] [TH]Case type[/TH] [TD]Rimless, bottleneck[/TD] [/TR] [TR] [TH]Bullet diameter[/TH] [TD]6.70 mm (0.264 in)[/TD] [/TR] [TR] [TH]Neck diameter[/TH] [TD]7.60 mm (0.299 in)[/TD] [/TR] [TR] [TH]Shoulder diameter[/TH] [TD]12.18 mm (0.480 in)[/TD] [/TR] [TR] [TH]Base diameter[/TH] [TD]13.30 mm (0.524 in)[/TD] [/TR] [TR] [TH]Rim diameter[/TH] [TD]13.00 mm (0.512 in)[/TD] [/TR] [TR] [TH]Rim thickness[/TH] [TD]1.40 mm (0.055 in)[/TD] [/TR] [TR] [TH]Case length[/TH] [TD]67.50 mm (2.657 in)[/TD] [/TR] [TR] [TH]Overall length[/TH] [TD]86.50 mm (3.406 in)[/TD] [/TR] [TR] [TH]Case capacity[/TH] [TD]5.58 cm3 (86.1 [URL='https://en.m.wikipedia.org/wiki/Grain_(unit)']gr H2O[/URL])[/TD] [/TR] [TR] [TH]Rifling twist[/TH] [TD]250 mm (1 in 9.84 in)[/TD] [/TR] [TR] [TH]Primer type[/TH] [TD]Large rifle magnum[/TD] [/TR] [TR] [TH]Maximum pressure[/TH] [TD]440 MPa (64,000 psi)[/TD] [/TR] [/TABLE] Base diameter is in line with the dimension indicated on the 7 LRM cartridge blueprint. Just saying, since I haven't measured it. Cartridge length of the 7 is 2.514", so this one is .143" longer. But you know...all this right now is just blowing wind! The fact of the matter is, my best choice for brass is unavailable at the moment. Odds are some will turn up by the time it's needed. For right now I have the 100 count of old Hornady brass that can be put to use. It can be sorted, and massaged, and maybe out of the 100 there will be 50 worth farting with, or maybe less. But it will get me that much closer! OK, so what's the next step? Order the Hornady bushing dies for 7 LRM? Who's going to have that? Then the reamer, right? It was mentioned that could be done with dummy dummy rounds. Truly? And what about the cartridge blueprint, with adjustments for neck reduction? Will that be necessary? [/QUOTE]
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Need technical input: rifle project based on 7LRM cartridge necked to .277
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