30 cal turned heads

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by qqqq33, May 1, 2009.

  1. qqqq33

    qqqq33 Active Member

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    ok experts why hasnt anyone just turned a longer monometal bullit for the 30 cal. Wouldnt that give it a higher bc. please give pros and cons and what to becareful of. I have the means to turn my own. was thinking of using a 338 lapua turned down to 30 cal
     
  2. FEENIX

    FEENIX Well-Known Member

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    I'm no expert but here's my WAG, ... time and $$$ vs ROI. With today's bullet design, I just let the barrel do the turning. :rolleyes::D:).

    Good luck!
     

  3. EddieHarren

    EddieHarren Well-Known Member

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    There's a fellow, over on AR, that is lathe turning solid copper bullets and having great success with them.
     
  4. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    I think that the limiting factor is the required twist to stabilize the bullet. You need to get up into the 8 or 9 twist to handle the long bullets. There really isn't any factory barrels out there that are that fast, so the market for the really high bc 30 cals is very limited. Also if you set up a rifle to handle the long bullet, it may not function well with conventional bullets.

    Just my .02, Steve
     
  5. BountyHunter

    BountyHunter Writers Guild

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    Almost everyone of those type bullets have had issues with barrels. Seems that you have to go thru gyrations finding exactly the right twist, right groove diameter, bore diameter combos etc to get a barrel to work.

    BH
     
  6. Michael Eichele

    Michael Eichele Well-Known Member

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    The properties of jacketed lead produce much higher BC's than solid copper. Length for length, design for design, shape for shape, jacketed lead will always have a higher BC than a solid copper bullet. If you made a bullet of the same length and dimensions as the 240 SMK, the SMK will have it beat by a fair margin, plus the all copper would require a tighter twist to boot. IMHO, solid copper is NOT the place to be looking for a ultra high BC bullet. Yes it will take more length to get the weight up and the theoretical BC should be higher but it really isnt. Length is NOT the only factor in a BC. Material density is also a big part. In short, a 240 grain all copper and 240 grain jacketed lead bullet of the same style might have very similar BC's but it is going to take alot of length to get that all copper bullet up to 240 grains. The additional length of the all copper will not offer you more BC than the SMK. You will also need a MUCH tighter twist to handle the length AND the all copper properties and for a BC that is no more than that of the 240 SMK.

    It seems like alot of money, time, effort and un-needed rifle torque for nothing in return.

    Now if you were talking solid lead, then the opposite would be true. Better yet, solid tungsten, but then again, barrel life would really suck if you used solid tungsten.
     
    Last edited: May 1, 2009
  7. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    I may be dead wrong, so someone correct me.

    To my reasoning an all copper bullet of the same weight and shape as the 240 SMK will be a longer bullet w/ the same shape. Has to have a higher bc. An all copper bullet that is of the exact same dimension as the 240SMK would be lighter with very nearly the same bc, slightly less. Substantially lighter means substantially faster velocity. To my way of thinking the faster slightly lower bc bullet will out run the slower slightly better bc farther than you can accurately range find.

    If I am wrong, I need someone much smarter than I am to explain it for me.

    Steve
     
  8. Michael Eichele

    Michael Eichele Well-Known Member

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    Copper has a specifec gravity factor of 8.89. Jacketed lead averages 10.7. The higher the SG, the higher the BC. The lower the SG, the lower the BC. Equal shape for equal shape jacketed lead wins. Same weight for weight, things will be similar in BC despite the longer length of all copper.

    Make sense?
     
  9. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    Makes sense. I knew the higher density material would make a higher bc. I suppose we can't figure out the the difference between the imaginary copper bullet and the 240 SMK as long as the copper bullet is imaginary. I would love to know the difference in bc between the the identical shapes and how much weight difference there would be, then translate that into relative velocities for each bullet. Then calculate drop and drift.

    So, someone needs to get busy on the lathe.:D

    Steve
     
  10. MontanaRifleman

    MontanaRifleman Well-Known Member

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    There is always going to be a trade off between mass, velocity and BC. It would stand to reason that a material with higher density would have a higher BC, all else being equal. On the other hand... higher mass means lower velocity. Usually though, the hevier and higher BC bullets will out distance the lighter faster bullets in the same cartridge.

    Then comes the question of application... paper punching or animal killing... and there are a lot of variables in that question.

    Generally speaking, my first priority in choosing a "hunting" bullet is accuracy (as long as it is IMO, a reliable killer). Next is terminal perfomance, i.e. monometal vs bonded vs non bonded, etc. Next is BC.

    So in some cases I might choose one bullet at a particular range and another at another range.

    Now when it comes to a bullet like the 300 SMK, that has all that mass, with BC to boot... it's hard to beat. But when we're looking at a 180 bullet in 7mm or 308, the trade offs become more interesting.

    Wouldn't it be boring without all the variables?
     
  11. qqqq33

    qqqq33 Active Member

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    ok i get the picture. But this brings up a new idea you said tungsten would give it more weight there for more bc. What if I made it with a tungsten insert what then.
     
  12. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    Did some loading yesterday to go out and do a little playing at distance. While loading saw this;

    180g Nosler Ballistic Tip B.C.= .507

    180g Nosler E-Tip B.C.= .523

    Michael, does this go along with what you are saying, or not? I know that last year I chose to use the E-Tip over the 200g AB because the increased velocity of the 180g E-tip out performed the 200g AB out as far as I could shoot. I would have to run the #s again but I think about a 1000 yards.

    Not looking for a dispute, looking for knowledge.

    Steve
     
  13. LouBoyd

    LouBoyd Well-Known Member

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    Lost River Ballistics (now out of business) used to make a 220 grain 30 caliber machined copper alloy (looks like brass) bullets with a G1 BC of 0.930. That was one of their J40 series. I've never seen a coment of anyone who's found them to shoot accurately, thoough no one argued about the high BC. Disucssions of why they don't shoot accurately just seem to be mostly speculation. They don't have engraving bands like the more succesfu Lehigh solids. The Barns 50's don't have engraving bands and they shoot well. Perhaps they''re just to long to stabilize well regardless of twist. Perhaps the tests were done at short range (under a mile) where the incredible low drag doens't offer a particular advantate.

    I built a 30" x 9" twist 300 RUM Rem 700 with the intention of shooting them but in setting up the rifle I found it shot 210 moly Bergers very well to over a mile. The Bergers are much less expensive. I still have several boxes of the LRB 220's waiting for a reason to try shooting them.
     
  14. MontanaRifleman

    MontanaRifleman Well-Known Member

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    Barnes has sort of done this. They put tungsten into the aft partof the bullet. It is a more dense bulletl and very spendy. They are still developing the line.