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  1. J

    Slow load for transonic stability evaluation?

    I will try to shed some light on this transonic stability topic. Ballisticians define gyroscopic stability (Sg) as (P^2)/(4M), where P is basically proportional to the bullet's instantaneous spin-rate (p) and M is sort of the instantaneous overturning moment (trying to tumble the bullet). We...
  2. J

    A Problem Unique to Long-Barreled Rifles

    Yes, straight-walled cases should have a WF of essentially 1.0 in QL, while the proverbial "50 BMG case necked down to fire phonograph needles" would be close to 0.10. I have had to use SS pressures of 12 ksi for some of my monolithic copper solids in QL, but usually around 8 ksi, even for them...
  3. J

    A Problem Unique to Long-Barreled Rifles

    The two things I adjust in QL to get closer agreement with chronographed MV are first Shot-Start pressure in the powder panel (for bullet hardness and throat roughness and angle) and then Weighting Factor in the cartridge panel (mainly for the amount of "necking down" of cross-sectional area in...
  4. J

    A Problem Unique to Long-Barreled Rifles

    This example load is accurate in the rifle for which it was developed because bullets exit when the muzzle is almost to an upward-moving halt, and because this exit timing provides positive "compensation" for the usual variation in muzzle velocities within a group of shots. Compensation involves...
  5. J

    A Problem Unique to Long-Barreled Rifles

    Yes, JB.IC, I see that the muzzle speed dy/dt function calculation got garbaged up since I had it correct a few days ago. I have been mostly working with the muzzle position y(t) function. I fixed it again. At bullet release, 1328 microseconds, the muzzle position is slowing almost to an upward...
  6. J

    A Problem Unique to Long-Barreled Rifles

    Windows will not let me compress an Excel file, 6.5SH. Here are pdf files of the paper which goes with a re-done workbook. There are many fewer simplifying assumptions made with this approach. It shows how the driving function and the resonant frequency responses occur at the muzzle. PDF...
  7. J

    Is it military mill rad or true mill rad?

    If you want your "mil" to be the angle subtended by one unit as seen from 1,000 units away, it had better be a true milliradian; i.e., 1/(1000*2*pi) of a circle. There are 6283.185308... milliradians per full revolution. Jim Boatright
  8. J

    A Problem Unique to Long-Barreled Rifles

    I really need to post the current Excel workbook. I believe Theis posted the earlier one in Resources, and this new one should replace that old one. But, I will need to send it to you as an email attachment. Only a couple of guys have asked me for one so far. Jim Boatright <[email protected]>
  9. J

    A Problem Unique to Long-Barreled Rifles

    Here is my finalized paper on the subject of tuning the rifle barrel and load together. I have tried to re-write both the paper and the spreadsheets for easier use and understanding. [I took out most of the equations and physics lectures.] I know the screenshots of the large spreadsheets are...
  10. J

    A Problem Unique to Long-Barreled Rifles

    While I have never tuned up a Ruger Precision Rifle, my suspicion about your horizontal spreads is that the three bolt lugs are either not supported symmetrically in the receiver design, or perhaps they are not bearing the load of bolt-thrust evenly due to uneven bolt-lug/seat engagements while...
  11. J

    A Problem Unique to Long-Barreled Rifles

    Not at all, Macht. It's just that nobody has ever formulated the vertical-plane shear-wave vibrations before to my knowledge. I do request input of the distance of the rifle CG below the bore line in formulating the amplitudes of the vertical-plane vibrations at the muzzle. Email me and I will...
  12. J

    A Problem Unique to Long-Barreled Rifles

    Well, at this level of analysis, the expected motion of the muzzle in the horizontal plane is ZERO. An asymmetrical receiver will cause some skewing of the plane of transverse barrel excitation. For a typical right-handed ejection port receiver, the shot scatter for different muzzle exit times...
  13. J

    A Problem Unique to Long-Barreled Rifles

    I have developed an Excel workbook of 4 spreadsheets which facilitates the input of the rifle, barrel, and interior ballistics data needed to calculate muzzle position in millimeters as a function of time since 10-percent of P-Max, as is used in QuickLOAD(c). You can enter your data, and the...
  14. J

    A Problem Unique to Long-Barreled Rifles

    Yeah, and I once explained to a NASA manager why a parallax correction had to be applied between the tracking radar data and the 60-feet away optical acquisition-aid pedestal's synchro data as "adjusting the synchro readings to making exactly 360-degree circles." They installed a coaxial CCTV...
  15. J

    A Problem Unique to Long-Barreled Rifles

    Good questions, Macht. Yes, I chose to ignore the higher-frequency striker caused vibrations, and those caused directly by primer ignition. I am also ignoring the often significant barrel vibrations caused by bolt slap during initial bolt-face loading. I am not really trying to calculate the...
  16. J

    A Problem Unique to Long-Barreled Rifles

    Yes, I used to shoot at the Pearland Sportsman's Club range with some of Virgil King's later hard-core benchrest friends. That was in the late 1960's and 1970's. Virgil became the night manager of one of the Houston Ship Channel's huge oilfield equipment storage warehouses. They had permission...
  17. J

    A Problem Unique to Long-Barreled Rifles

    I am in the process of developing an Excel workbook of spreadsheets which will allow serious riflemen and riflesmiths to enter basic data for candidate rifle barrel-cartridge-bullet-load combinations and produce data showing the vertical-plane muzzle motions caused by transverse barrel...
  18. J

    A Problem Unique to Long-Barreled Rifles

  19. J

    A Problem Unique to Long-Barreled Rifles

    Yes, I worked with Al Harral ten or twelve years ago on chamber wall and bolt-lug triaxial von Mises stress calculations. I was successfully able to hand calculate stresses for a few key points which agreed well with his LS-DYNA computer program results. Back then, we "agreed to disagree" about...
  20. J

    A Problem Unique to Long-Barreled Rifles

    I was asked several years ago by David Tubb to explain ballistically why crosswinds favored riflemen shooting barrels made with twist direction matching the crosswind direction--L to R winds favoring LH twist barrels, and vice-versa. I could find...
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