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  1. J

    Bullet shockwave footage

    Here is my final version of the paper on Barrel Obturation with 338-Caliber Copper Bullets:
  2. J

    Bullet shockwave footage

    Here is a picture of some base-drilled and undrilled bullets recovered from a swimming pool. The top bullet is unfired. The next one was not base-drilled. Note the large gas leakage paths in the groove edges. The lower two bullets were base-drilled to the depths indicated by the black annotation...
  3. J

    The new 33XC & 37XC cartridges designed by David Tubb

    I agree, Dan. Also I never recommend any type of neck turning when it can easily be avoided with adequate neck clearance and best quality brass, say about 3 thousandths more than the loaded round. I also avoid "pull type" neck expanders in precision reloading and always use "bushing type"...
  4. J

    Hyper Stabilized Bullets - Jim Boatright

    Your second point first, Alan; I did consider the hardness of the copper material of these bullets by citing a minimum yield strength rating of 40,000 psi for this presumably "half hard" copper. It could be anywhere from 18 to 60 ksi, depending upon the amount of work hardening it received. You...
  5. J

    Hyper Stabilized Bullets - Jim Boatright

    Rather than specify a non-standard groove depth for the barrel, I would recommend enlarging the sealing OD of the copper bullet by 0.0008-inches to provide maximum static contact pressure of the bullet inside the grooves. Even so, a copper bullet cannot match the contact pressure of a...
  6. J

    Bullet shockwave footage

    If one looks carefully at the Schlieren video of the shocks exiting the muzzle of the rifle barrel during firing, one can observe the gas leakage past the bullet within the barrel exiting ahead of the bullet itself. The bullet is going at about Mach 1.2 at the time of peak base pressure behind...
  7. J

    Hyper Stabilized Bullets - Jim Boatright

    I am currently thinking to use 0.125-inch base drilling for all 338-caliber bullets, and probably also for 375's and larger calibers. For 30-caliber and smaller bullets, we should use proportionally smaller diameter drills, possibly limited by drill bit strength and rigidity for manufacturing...
  8. J

    Hyper Stabilized Bullets - Jim Boatright

    Sorry, but I did not photograph those test bullets. We test fired one each of the copper 338 bullets having various (8 or 10 different) hole diameters and drill depths into Chuck Pierce's swimming pool using full power 338 LM loads. All of the base-drilled bullets behaved exactly as I described...
  9. J

    Hyper Stabilized Bullets - Jim Boatright

    Here is a new paper I just finished explaining proper barrel obturation (gas sealing) with monolithic copper bullets. It explains one of the main reasons for base drilling these copper ULD bullets--base pressure ducting to the inside of the gas sealing ring. Good barrel obturation will go far...
  10. J

    Bullet shockwave footage

    Bullet designers usually try to minimize the TOTAL AERODYNAMIC DRAG of their bullets when they are flying at about Mach 2.5 with zero angle-of-attack. The total drag is comprised of meplat drag, headshape drag, skin friction, driving band drag, and base drag. For example, truncating the long...
  11. J

    The new 33XC & 37XC cartridges designed by David Tubb

    It looks like the 33XC chamber is 0.35-inch longer than that of a 338 LM, so COAL would run about 4.50 to 4.60 with long copper bullets seated out.
  12. J

    ELR bullet recovery

    Frank, if you ever want to know a bullet's spin-rate in flight, just first calculate its initial spin-rate as MV/Tw (in feet per turn), then multiply that by an exponential decay factor given by exp[-tof/(cal/0.0321)] where "tof" is time of flight in seconds and "cal" is the bullet caliber in...
  13. J

    ELR bullet recovery

    I have recovered lots of WWI and WWII-era jacketed rifle bullets which have eroded out of old berms. Some of them are in remarkably pristine condition. The copper jacket material does not pit when oxidized. They just get darker colored with age and weathering. The exposed lead-alloy cores do...
  14. J

    ELR bullet recovery

    Pure copper in its annealed state has a yield strength of about 18,000 psi. It readily work hardens to 40 ksi or even 60 ksi. Work hardened copper tools were used by prehistoric people to fell trees and carve wood. Bronze and brass alloys are stronger still. The gilding metal bullet jackets are...
  15. J

    Bullet shockwave footage

    Nice imaging set-up. He did not mention how he triggered the high-speed video camera though. I hope my bullet design flies a lot cleaner than that 50-caliber bullet. I expect it to produce major bow wave and base shocks, and minor ones only at base of ogive, start of rear driving band, and start...
  16. J

    ELR bullet recovery

    In developing my new solid copper ULD bullet, we have fired a bunch of them into the deep end of a swimming pool and recovered them quickly. We are primarily reading the bullet engraving marks and the sooting patterns to check bullet obturation from different rifling patterns, but have noticed...
  17. J

    The new 33XC & 37XC cartridges designed by David Tubb

    I fear my earlier reply to this question from Skookum got lost when my internet service went down. I cannot foresee any possible deleterious effects of shifting the tripping ring back about an inch behind the tip of any rifle bullet. For those bullets which can benefit from adding such a ring...
  18. J

    The new 33XC & 37XC cartridges designed by David Tubb

    Yes, you have the right ideas about laminar versus turbulent flow in the boundary layer. You can sometimes just make out the thin boundary layer in high-resolution shockwave photographs of supersonic bullets. The laminar (layered) flow-fields are smooth in cross-section, while the turbulent flow...
  19. J

    The new 33XC & 37XC cartridges designed by David Tubb

    No, I meant to recommend placing the ring about 1 inch from the tip of the bullet. The maximum distance over which the boundary layer flow can remain laminar is about 1.25 to 1.50 inches, depending upon what value the "critical Reynolds Number" turns out to have. McCoy says one can safely assume...
  20. J

    The new 33XC & 37XC cartridges designed by David Tubb

    David Tubb's idea of ringing the noses of long-range rifle bullets is great for any bullets designed with tangent ogives, any multi-ogive bullets, and any secant-ogive bullets having RT/R ratios greater than about 0.5. This "turbulator" ring serves aerodynamically to "trip" the initially laminar...
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