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  1. J

    Dope shooting uphill - tell me why I'm wrong

    I consulted with Ted Almgren and the late Bill McDonald of Sierra on their uphill/downhill shooting correction. I believe that my formulation is equivalent to theirs, but simpler in application. Slant Range (R) and slope angle (A) are directly measured in the field nowadays. A table of "total...
  2. J

    Dope shooting uphill - tell me why I'm wrong

    One of the first solutions suggested is the old "rifleman's rule" which is only a first order approximation. It is no longer adequate for accurate modern rifles. My "total drop from bore axis times [1 - Cos(Theta)]" solution is physics based, but is not quite a full 6-degree of freedom...
  3. J

    Can a different muzzle device change barrel harmonics and effect accuracy

    Yes, Greg, I worked with Al Harral (VarmintAL) comparing his LS-DYNA FEA triaxial stress calculations with my hand calculations at several key locations on the bolt face, bolt lugs, and barrel swell for a Remington Model 7 in 243 Win. They agreed, but Al did not think that was possible. Many...
  4. J

    Can a different muzzle device change barrel harmonics and effect accuracy

    Yes, Vic, tightening 60-degree V-threads radially compresses the barrel steel inside the loaded threads and inside the nearby load bearing surface, and it can be a lot if you crank on any threaded joint. The greatest compression is just inside the receiver face with threaded barrels and just...
  5. J

    Can a different muzzle device change barrel harmonics and effect accuracy

    I did all of my barrel vibration calculations for a barrel temperature of 21 degrees Celsius (C). Using the handbook decrease in Young's Modulus of Elasticity for all steels of about 5.0 GigaPascals (-5 GPa) per 100 degree C temperature increase, and using a coefficient of linear thermal...
  6. J

    Dope shooting uphill - tell me why I'm wrong

    First, measure the true "slant range" R to your target, as you would using a rangefinder. Second, measure the slope angle THETA above or below the horizontal for your line-of-sight to that target. Then calculate the total drop D from the axis of your bore when firing your rifle horizontally to...
  7. J

    Imperial Sizing Die Wax

    Imperial Sizing Die Wax is essential for precision rifle reloading. Benchresters swear by it. I have used it exclusively for over 40 years, and I'm on my third can. If you use a container of it in less than 10 years of shooting, you are applying way too much of it. Just a thin coat on the case...
  8. J

    A Problem Unique to Long-Barreled Rifles

    Each barrel vibrates independently at any number of different naturally resonant frequencies fn. I calculate the first 7 vibration modes in the spreadsheet. These are all shear-wave vibrations in a vertical plane traveling along the steel barrel at over 10,000 fps and reflecting off each end of...
  9. J

    A Problem Unique to Long-Barreled Rifles

    1. The mathematical description of vibration modes gets much more difficult for rifle barrels made of non-isotropic materials such as carbon fiber wrapped steel core barrels. While firing results might be better, putting numbers on the muzzle motions would not be practical (at least to me). 2...
  10. J

    A Problem Unique to Long-Barreled Rifles

    Dr. Franklin Mann, author of The Bullet's Flight (1909), experimented with many different rifle and barrel support setups, including clamping the muzzle of a barrelled action into a heavy rigid vise. I do not recall that he found any approach consistently better than using proper benchrest...
  11. J

    A Problem Unique to Long-Barreled Rifles

    Yes, one could do all that, but it would be extrapolating to the absurd. I am trying to allow real rifles to fire CNC turned copper bullets to achieve their full designed-in aeroballistic and accuracy performance levels. Any way they can be launched into ballistic flight with consistent muzzle...
  12. J

    A Problem Unique to Long-Barreled Rifles

    Yes, one is always tempted to generalize before all the data is known. This problem of recoil-caused barrel vibrations affecting muzzle motions at bullet exit time is complicated because the muzzle motions at any instant are always the algebraic sum of at least three disparate resonant...
  13. J

    A Problem Unique to Long-Barreled Rifles

    Thanks, Earnhardt. So far, only one guy has requested the new Excel spreadsheet, though. And he is from Slovenia.
  14. J

    A Problem Unique to Long-Barreled Rifles

    If a load and barrel combination is not going to work, shooting 2 or 3 shots is enough to determine that fact. If the combination looks promising, then shoot 5- or 10-shot groups for confirmation. Most modern benchrest competitions measure 5-shot groups for extreme center-to-center spread; like...
  15. J

    A Problem Unique to Long-Barreled Rifles

    For most rifle barrels not having massive muzzle attachments, the front portion of the barrel bends up or down about a pivot point located about 20-percent of the barrel length L behind the muzzle. If the muzzle is moving vertically upward (positive Delta-V) at the group mean bullet exit time...
  16. J

    A Problem Unique to Long-Barreled Rifles

    I doubt that one could visually detect muzzle vertical displacements from its neutral position of well under 0.100 millimeters with all the commotion of firing the rifle. These vibration amplitudes are small, but their effects are mighty. However, the cross-track acceleration of the muzzle might...
  17. J

    A Problem Unique to Long-Barreled Rifles

    Hello again, all; I have not been entirely idle during this pandemic and ammo component shortage. I have installed a new Oehler System 89 BC Chronograph in my indoor test range. I have developed a new working theory about why my long copper bullets have been inaccurate and produced highly...
  18. J

    Slow load for transonic stability evaluation?

    The differences among high-drag slugs and very-low-drag (VLD) bullets in terms of the airspeed boundary between subsonic and transonic airflow regimes is about Mach 0.80 for blunt bullets and Mach 0.90 for "streamlined" bullets. This is about 100+ fps difference in airspeeds in most surface...
  19. J

    Slow load for transonic stability evaluation?

    Yes, initial Sg is theoretically independent of muzzle velocity V(0), but it is highly sensitive to ambient air density (rho). The initial spin-rate (p) of the rifle bullet is V(0)/Tw, where Tw is rifling twist-rate in feet per turn. I mentioned that Sg is proportional to (p/V)^2. Right out of...
  20. J

    Slow load for transonic stability evaluation?

    I am disturbed whenever I hear bullet airspeeds (V) expressed in feet per second (fps) used in discussing the breakpoints between supersonic, transonic, and subsonic flight regimes. What kind of bullet is it and what are the local atmospheric conditions? Airspeeds must be expressed as Mach...
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