Guy Neill

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About Guy Neill

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  • Birthday 09/04/1951

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  1. I calculate directly, beginning with finding the gun velocity with a momentum balance. The gun momentum equals the ejecta momentum (bullet plus powder gases. Once the gun velocity is obtained, insert it in the kinetic energy formula to get the free recoil energy. It's described in Hatcher's Notebook as well as some other sources. I've attached a brief description.Momentum balance I put it into a spreadsheet some time back. I hope it's helpful Guy Recoil Calc 6-23-17.pdf
  2. With the 36 ounce gun, and the values you give, I find; Cartridge 9mm 40 40 Minor Minor Major Bullet 147 180 180 Velocity 925 725 950 Charge 3.5 3.2 4.2 Momentum 0.67 0.64 0.84 Gun Velocity 9.5 9.1 11.9 Recoil (no charge) 2.6 2.4 4.1 Recoil (with charge) 3.2 2.9 5.0 Guy
  3. Do these values include the powder charge? Did they way what gas velocity they use? My numbers vary a bit - though it is generally a relative comparison. Looking at the Major load, for example, using your 36 ounce (2.3 pound) gun, I have the momentum as 0.85, as they show, but the gun velocity I show as 12.1 fps. The corresponding recoil energy using the bullet alone, with no powder is 4.1 ft-lbs. Assuming 5 grains of powder and a gas velocity of 4000 fps, recoil becomes 5.1 ft-lbs by my calculation. Did they list the equation? The calculation as shown in several references is a momentum balance to determine the gun velocity, then using that in the energy equation. Thanks. Guy
  4. If you want numbers yo compare, I need the following; bullet weight bullet velocity powder charde gun weight for each Guy
  5. Power factor is the bullet weight, in grains, times the velocity, in fps, divided by 1000. As I recall, in Limited, to qualify for Major, it must be at minimum 40 caliber. You can use 9mm, but it will score as Minor no matter the actual power factor. Equipment would be a scale to weigh bullets, a chronograph to measure velocity and a calculator to do the calculation. Some chronographs will do the calculation for you Guy
  6. I believe Hornady and Speer have bullets intended for the 7.62x39. Guy
  7. Did any of the light primer strikes fire on a second try? The 0.003" should be suitable unless the anvil legs are not against the bottom of the primer pocket. This could be that primers are on the shorter side and/or the primer pockets are on the deeper side. You might try one or two things. First - how does it do with factory ammunition? If factory ammunition gives the same problems you may suspect the gun, Alternately, load a batch of ammunition and sort by primer seating depth, looking for a group 0.005 - 0.006 inch deep see how they work in the gun. Guy
  8. With normal tolerances, the primer face should be 0.003 to 0.005 inches below the case, though I have seen factories allow anything from 0.000 to 0.008 inches. Overall, what you want is the primer anvil legs against the bottom of the primer pocket. The three to five thousandths usually gives reliable performance. Guy.
  9. I don;t recall all the powders I tried some time back, with photos in the dark, but my experience with HS-6 was like a flash bulb going off in front of my face. If I'm remembering right, the Vihtavuori powders were fairly low flash, and I don't recall 231 being too bad. Guy
  10. Never having used one, I'll defer to those with experience with a Ransom rest. Do slower burning powders tend to rotate it more? Or is there a guideline? Thanks. Guy
  11. You may want to shoot for a velocity of 945 fps with your 180gr bullets. This would give a 170 power factor that should be good most anywhere. What online calculators are giving different values? Guy
  12. Trying to use the values listed for Titegroup and WSF, here’s the difference. Using a 3 pound gun and equal velocities of 865 fps for 230 grain bullet, and 5.2 grains of Titegroup and 6.7 grains of WSF. Charge Velocity Recoil Acceleration Force PF Titegroup 5.2 865 5.3 1795740 1834 199 WSF 6.7 865 5.6 1795740 1834 199 Since the bullet is accelerated to the same muzzle velocity, the acceleration value, and subsequent force must be equal. Recoil is in ft-lbs using the gun velocity and mass. Force is in pounds, acceleration is fps2. Power factor is a form of momentum with inconsistent units (grains-feet/second instead of pounds-second) resulting from wv instead of mv. Another aspect of what we feel ins the moment. This is the force times the distance between the bore and our hand. In the case of the Ransom rest, it is the distance between the bore and the pivot point of the rest, likely greater than the distance between the bore and the pivot point of our hand. If, for the sake of argument, we assume the distance between the bore and the pivot point of our hand is one inch, the moment arm would be 153 ft-lbs with the force determined earlier. This seems a lot, but it is applied very briefly (0.0005 seconds). I tend to expect the moment is more a factor in the rotation of the Ransom rest than recoil (though obviously they are not totally unrelated). For equal power factors (resulting in equal force) the rotation should be equal, though there will be variations just as we see in load tests with velocity variations. It seems likely approximations could be calculated, though I find angular calculations more tedious than linear ones and have not pursued it further at this time. While all this is interesting, it still comes down to how the shooter perceives the recoil – the combination if the actual recoil plus the muzzle flip caused from the moment arm. In my own shooting, if I’m doing my part, the load doesn’t seem to matter much other than accuracy. I’ve done some of my best shooting with heavier loads. As such, I select components that are available and satisfactorily economical, develop an accurate load – and go shoot. No particular worry about finding the mathematically lowest recoil load. Others may find they are more prone to the recoil feel and should experiment to see what works for them. Guy
  13. Hatcher states: "Bevis and Donovan, in The Modern Rifle, 1917, state that experiments with a Seibert Velocimeter lead to the conclusion that a value of 4700 may be used for the exit velocity of the gases. Balleisen, in Principles of Firearms, 1945, gives the same figure." Guy Guy
  14. As you quote, the multipliers come from the British Textbook of Small Arms 1929. Hatcher's 4700 value comes from his latter 1950's book. Quickly scanning the book, I do not see teh individual factors as listed by SAAMI, but the statement that the value will be between 1 and 2, to be determined by experiment, but generally as 1.5. It has been said the 4700 value is applicable to artillery, and the 4000 to small arms. I've also seen recommendations to use 2000 for black powder. Which is "best"? I don't know, but as long as one system is used for side by side comparison, it should give a relative comparison. As a comparison, let's look at the aforementioned 20gr bullet at 850 with 5 grains of powders versus a 250gr bullet at 680 fps with 4.2gr of powder. Bullet Bullet Powder Recoil Recoil Recoil Bullet Only Weight Velocity Charge 4700 4000 SAAMI Recoil ---------------------------------------------------------------------------------------------------------------- 200 850 5.0 4.0 3.8 3.8 3.1 250 680 4.2 3.8 3.7 3.7 3.1 These have equal momentum (power factor) but we see the heavier bullet gives less recoil energy through the use of less powder. Guy
  15. The power factor is a momentum value while recoil is more commonly an energy value. Momentum id mass times velocity. Energy is one-half mass times velocity squared. The value of 4000 for the powder gas velocity is a more recent figure. Hatcher, in his book, listed 4700 for the powder gas. As someone stated, either can be used as it will still rank the relative values. I tend to stay with the 4700 value, since that is what I've been more used to. The powder charge is a significant portion of the recoil. As an example, the recoil due only to the bullet for a 200 grain bullet at 850 fps gives a recoil value of 3.1 ft-lbs. Using 5 grains of powder brings the recoil to 4 ft-lbs, comprising 13% of the total. In rifles the powder may produce more recoil than the bullet. Guy