Whats the most stable transonic bullet?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Topshot, Mar 29, 2011.

  1. Topshot

    Topshot Well-Known Member

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    Hi,

    I am interested to finding out your ideas on what type of bullet design is best suited to survive shooting through the transonic barrier.
     
  2. 300magman

    300magman Well-Known Member

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    I'm not sure what help this will be to you, but it might be worth looking at the bullets used by long range black powder shooters. I haven't gotten around to actually doing it, but a while back I was asking questions about the old 45-70 round and how anyone managed to hit anything accurately with it at extended ranges, when clearly it was going to go subsonic less than half of the way there.
    Apparently certain bullet shapes are much preferable to others, and a quick search would probably turn up the top contenders for you. Obviously they are very large bullets, 450gr at the low end, and they don't start out very fast, but they do start out above the transonic zone and quickly transition into it, and then through to subsonic velocities, within the first several hundred yards of thier flight.
     

  3. Oliveralan

    Oliveralan Well-Known Member

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    I'm writing a research paper for a school project on this. Over the summer I will be testing a host of 30cal bullets from a .308 win. As this is arguably the most common "LR" caliber and has a huge range of bullet types and weights.

    I will closely be following this thread as i will within the next couple months begin extensive testing. I will then try to draw a conclusion as to physical aspects of a bullet at keep them stable when going transsonic.
     
  4. Bravo 4

    Bravo 4 Well-Known Member

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    If I was gonna take a guess (and that's all I'm doing) I would say that bullets with a higher rpm would be effected more. Maybe that's why a big slow 45-70 round can be so accurate past it's transonic range.
     
  5. Topshot

    Topshot Well-Known Member

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    The 308 is also one of the cartridges that I am interested in. I have been testing the 155 grain HBC bullet at 1200 yards out of my 24" bull barrel. This has given me some interesting results.

    However the odd bullet that bites the dust has lead me to search for a better bullet to make it to the target more consistently.
     
  6. elkaholic

    elkaholic Well-Known Member

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    Good luck with your research! I will be very interested in hearing the results.....Rich
     
  7. Gene

    Gene Well-Known Member

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    How do you measure "transonic". The most aerodynamically efficient bullets are secant ogive, high BC, notwithstanding the caliber.
     
  8. Buffalobob

    Buffalobob Writers Guild

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    The old M118 special ball bullet which was a173 gr FMJBT was stable through the transonic. The bullet was made by the Lake City Arsenal and is not to be confused with any SMK. You can probably find a few on Ebay. They were also loaded in 30-06 as the M72. Why they were stable is not clear to me but I believe the boat tail was very shallow. The dies that were used to make the bullet wore out and the QC became erratic and production was terminated.
     
    Last edited: Mar 31, 2011
  9. Topshot

    Topshot Well-Known Member

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    Gene,
    What I am interested in is bullets that can go from supersonic speed to sub-sonic speed and still maintain a high degree of accuracy.

    This is important when shooting calibres like the .308 that can go sub-sonic when shooting out near 1000 yards.

    A lot of VLD type High B.C. bullets are easily upset going through the transition. A less aggressive bullet may be better in this case. The question is which one?
     
  10. Gene

    Gene Well-Known Member

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    I cannot answer your question. Perhaps an aeronautical engineer could. I suggest you contact Bryan Litz at Berger bullets. He would be the best authority to respond. The answer might be in his recent book.
     
  11. groper

    groper Well-Known Member

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    Topshot, short answer- in Your .338cal, try the lapua 250gr lockbase.
    Long answer- projectiles with relatively short length and shallow angle boat tails or no boat tail at all have better stability throughout their flight, particularly transonic. Finer meplat dia helps also as does a better transverse to axial inertia ratio.
     
  12. Topshot

    Topshot Well-Known Member

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    Groper,

    I will check them out.

    How long till your projectiles are ready for me to test?:D
     
  13. groper

    groper Well-Known Member

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    Still waiting for bill to get back to me on the 338's ...
     
  14. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    I agree with Gropers assessment of what geometric and mass properties are good for a bullet's transonic stability.

    A recent example of such a bullet is the Berger 175 Tactical OTM which I designed specifically for transonic stability:
    308Tactical

    Increasing twist rate can help a little, but the biggest outside influence is atmospherics. Many bullets that are not transonic stable at sea level are so at 3000+ feet elevation.

    -Bryan