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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
7 mm SHERMAN SHORTMAG vs 7 SAUM
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<blockquote data-quote="ormandj" data-source="post: 2329562" data-attributes="member: 110065"><p>1:8 or 1:8.5 twist for a 7SS in a 20" barrel? I'll be using temperature stable powder, so no RL26 (have VV N565 to start with). I have no idea what bullet(s) I will be using. My range is out to 1760 yards, and I will also be hunting. I will be feeding from binderless box magazines (max COAL of 2.960", but I'd prefer to keep it 2.940" or less for reliable feeding). If the 190s/etc don't make sense in a 20" w/ the 7SS with this COAL limitation, then it's easy, I'll just go with the 1:8.5. The reamer is a standard reamer, as well. If they do, then read on!</p><p></p><p>I've asked everyone (thanks for the feedback [USER=13833]@elkaholic[/USER] !) and am just looking for a few more opinions since the barrel mfg, the gunsmith, and the cartridge designer all have slightly different opinions. They're all in the 1:8 to 1:8.5 range, and if I knew what bullet(s) I wanted it'd be easy. I'd just do a 1:8 if I knew I'd only shoot the 190+ or solids, but I don't know if that will be the case - I'll be shooting whatever my barrel likes best.</p><p></p><p>I've read SGs above 2 can cause some issues, and depending on the bullet and the temperature (I shoot in TX and in New England, so 100F+ down to 0F+), the 180s will be slightly above 2 SG in higher temperatures in TX, which makes it a bit tricker. That said, 1:8.5 drops the SG below 1.5 in colder temperatures with the 190-195s and some solids at the lower muzzle velocities I'm expecting due to the shorter barrel. I'm calculating based on ~2800fps with the 180-class and ~2700fps with the 190-class, which are hopefully somewhat reasonable for an _accuracy_ load in the 20" barrel (not max velocity) using temperature stable powders (no RL26, again).</p><p></p><p>Any tips will be helpful. I don't intend to shoot the really light bullets, I'd switch to another caliber for that kind of stuff (I have an 8 twist 6.5 Creedmoor if I want to shoot smaller critters), so it'll all be 170 and up for traditional bullets (monolithic might be different).</p></blockquote><p></p>
[QUOTE="ormandj, post: 2329562, member: 110065"] 1:8 or 1:8.5 twist for a 7SS in a 20" barrel? I'll be using temperature stable powder, so no RL26 (have VV N565 to start with). I have no idea what bullet(s) I will be using. My range is out to 1760 yards, and I will also be hunting. I will be feeding from binderless box magazines (max COAL of 2.960", but I'd prefer to keep it 2.940" or less for reliable feeding). If the 190s/etc don't make sense in a 20" w/ the 7SS with this COAL limitation, then it's easy, I'll just go with the 1:8.5. The reamer is a standard reamer, as well. If they do, then read on! I've asked everyone (thanks for the feedback [USER=13833]@elkaholic[/USER] !) and am just looking for a few more opinions since the barrel mfg, the gunsmith, and the cartridge designer all have slightly different opinions. They're all in the 1:8 to 1:8.5 range, and if I knew what bullet(s) I wanted it'd be easy. I'd just do a 1:8 if I knew I'd only shoot the 190+ or solids, but I don't know if that will be the case - I'll be shooting whatever my barrel likes best. I've read SGs above 2 can cause some issues, and depending on the bullet and the temperature (I shoot in TX and in New England, so 100F+ down to 0F+), the 180s will be slightly above 2 SG in higher temperatures in TX, which makes it a bit tricker. That said, 1:8.5 drops the SG below 1.5 in colder temperatures with the 190-195s and some solids at the lower muzzle velocities I'm expecting due to the shorter barrel. I'm calculating based on ~2800fps with the 180-class and ~2700fps with the 190-class, which are hopefully somewhat reasonable for an _accuracy_ load in the 20" barrel (not max velocity) using temperature stable powders (no RL26, again). Any tips will be helpful. I don't intend to shoot the really light bullets, I'd switch to another caliber for that kind of stuff (I have an 8 twist 6.5 Creedmoor if I want to shoot smaller critters), so it'll all be 170 and up for traditional bullets (monolithic might be different). [/QUOTE]
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7 mm SHERMAN SHORTMAG vs 7 SAUM
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