Sectional density understanding

Discussion in 'The Ammo & Reloading Forum' started by zkovach, Dec 6, 2017.

  1. zkovach

    zkovach Well-Known Member Supporting Member

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    ive read the definanition and doesn’t tell me much. Does sectional density have anything to do with a projectile easily mushrooming on game? What I mean is should a lower SD be used on a whitetail and a higher SD on say a moose?

    Reason why I’m asking is I want to slow down a 300 saum load for whitetail deer for proper expansion so I thought maybe I should go with a heavier projectile. Would my heavier projectile have trouble expanding ? Does sectional density have anything to do with that?

    Thanks guys!
     
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  2. carver

    carver Moderator Supporting Member

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    I don't know anything about sectional density. And don't care. I just choose the right caliber for the job, and let her fly!
     
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  3. sharps4590

    sharps4590 Well-Known Member

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    No, sectional density is purely a weight to diameter calculation. A 225 gr., 8mm bullet has a higher sectional density than a 150 gr., 8mm bullet. Caliber is the same, weight is significantly different. It does have an effect on penetration but not expansion. A perhaps oversimplification is that a 160 gr., 6.5mm bullet will penetrate deeper than a 150 gr., 7.62 bullet. Expansion is controlled by bullet construction as related to velocity. A bullet designed to expand at a moderate velocity of 1600 to 2000 fps is not as heavily constructed as a bullet designed to expand at velocities of 2600 to 3000 fps. Then you get into varmint type bullets as compared to dangerous game bullets. Opposite ends of the spectrum but you get the idea.
     
    Last edited: Dec 6, 2017
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  4. sharps4590

    sharps4590 Well-Known Member

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  5. zkovach

    zkovach Well-Known Member Supporting Member

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    Thanks for the info! So how do you know which bullets are designed to to mushroom easier? Is there info in the reloading books that explain which is a heavily constructed or lightly constructed bullet? Or is this mostly ballparked at different calibers?
     
  6. jsjj388

    jsjj388 Well-Known Member

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    typically if you research a bullet youll find either directly from the manufacturer, or independent tests, the speed at which a bullet will reliably expand.
     
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  7. Twicepop

    Twicepop Well-Known Member

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    Several years back I read a piece from a noted gun writer with a situation like you're describing. The writer's wife, a petite woman enjoyed hunting, but was recoil sensitive because of her size. The writer had built her a smallish rifle on a SAKO Vixen action, chambered for 6MM/222. Suitable light big game bullets weren't available in the 6MM size at that time. The writer surmised that a varmit bullet usually launched at 33-3500 fps or so might act like a large game bullet when pushed along at around 27-2800 fps. The tests he did in ballistic gelatin and stacked meat and rib combinations confirmed what he was thinking. The bullets mushroomed like a big game bullet and didn't shed their jackets. If I remember the article correctly he also said the rifle/bullet/load combination accounted for several head of antelope and mule deer.
     
    Last edited: Dec 7, 2017
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  8. sharps4590

    sharps4590 Well-Known Member

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    Can't add anything to what jsjj and Twicepop said. Depends on how much work you want to put into it.

    You can't ascribe it to a caliber. A good, jacketed hunting bullet for the fairly sedate velocity of a 25-35 Winchester cartridge will be completely inadequate in a 25-06 at 3000+ fps although they can be the same weight. It works the same across the spectrum of calibers. What's good for a 22 Hornet might come apart in a 220 Swift, 22 Cheetah or 22-250.

    20+ years ago I was using a 300 Win. Mag. in a Ruger #1 and had worked up an accurate load with a 165 gr. Hornady bullet. Problem was that particular bullet was intended for 2600-2700 fps and I was running it around 3150 fps, across the screens. I shot a muley doe with it at about 125 yards. It killed her where she stood but it wasn't pretty. The bullet did get into the vitals but I am fairly certain it was already fragmented. No exit and the inside of the off side rib cage looked as if it had been sprinkled with copper and lead fragments.

    These days I shoot cast bullets for game and don't worry about it. They always work and I've never had one fail.
     
    Last edited: Dec 7, 2017
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  9. drymag

    drymag Well-Known Member

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    As new bullets come out some interesting results have been popping up. Yet as sharps mentions, old school still works great.
     
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  10. zkovach

    zkovach Well-Known Member Supporting Member

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    Ok looking for suggestions on slowing down a 300 saum. Should I light load a 150-180 grain projectile or standard load a heavier 200-220 grain? My concern is over penetration without or with little expansion. Any suggestions? I typically hunt with nosler if that makes any difference . This would be for whitetail deer
     
    Last edited: Dec 7, 2017
  11. m77user

    m77user Well-Known Member

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    My opinion only. If you use Nosler bullets I would try a 180 Accubond with a starting load that is shown to be the most accurate with that bullet in the Nosler Manual. Velocity shown in the Nosler No. 6 manual with H 4831 sc is 2680 and is the lowest shown for the 180 grain bullet. I wish you success in finding what works for you and also in your hunts.
     
  12. zkovach

    zkovach Well-Known Member Supporting Member

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    I went on Craigslist tonight and really scored! I’m getting back into reloading now that my kids are a little older. I found 4 boxes of nosler 180 grain partitions, tons of 30-06 brass, 20 bullet boxes, auto primer, trigger pull gauge, 2-bottles of powder, and some other odds and ends for 100 bucks! So I’ll start loading that 300 saum with those partitions. I to to pick up a couple things like a new press, and scale. I’m excited to get that tumbler running again!
     
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  13. sharps4590

    sharps4590 Well-Known Member

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    I'd say you really scored!!! Congrats!! I don't believe I've ever bought a box of Nosler Partition's in my life but expect those 4 boxes were worth the "C" note!

    Welcome back to handloading, good luck and have fun with it!!!
     
  14. zkovach

    zkovach Well-Known Member Supporting Member

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    I’ve actually never bought the partitions because they were so much more expensive over the other nosler projectiles which always dropped deer. I’m pretty pumped!