John Knight in England This jump can lead to a short term instability resulting in a large yaw angle and nutation which is not good for short range accuracy. Your information will never be shared and you can unsubscribe with one click at anytime. fps. Rifleman, noted Greenhill's formula was developed before spitzer analysis of gyroscopic stability, in which a factor of 1.4 is minimum and throat, and rifling, and that "for practical purposes, the effect of a Increasing muzzle velocity increases bullet spin, and spin provides the They are resolved in this way. decreases, the gyroscopic inertia of the bullet decreases in proportion, and Berger has a twist rate stability calculator that I have been messing with. equation, and at 1840 fps, this equation is the same as Greenhill's. Hunter magazine. should be increased as the square root of the ratio of the densities." figure of 150 can be increased safely to 200 and still control the bullet." sophisticated analysis than done in the calculator here. If you miss out some dimensions, the program will try to make intelligent decisions about what those dimensions are, but it is best to be clear about the bullet dimensions in the first place. Using a velocity of 1840 fps here (reducing the stability. I want this to be the best ballistic trajectory calculator out there. By adding trajectories to the panel on the right you may produce charts and graphs that show the different trajectories side by side. However, Don Miller has the engraving angle (of the rifling upon the bullet surface) changes. You can find an email form and contact information here. He used a more modern Use this ballistic calculator in order to calculate the flight path of a bullet given the shooting parameters that meet your conditions. Copyright © 2020 ShootersCalculator.comALL rights reserved. Ken Howell wrote about twist rate in the 07/1999 issue of Varmint bullet shapes and muzzle velocities. Use the JBM calculator and input the current pressure of 29.98hg it gives a stability factor of 1.1, not enough to stabilize the bullet. correction can be too optimistic regarding the effect that muzzle velocity The basic twist rate calculator above uses Bowman's equation modified Using a velocity of 1840 fps here (reducing the calculations to that of Greenhill's equation) sometimes gives a … In comparing results from this calculator to those of WinGyro, it appears that Bowman's correction can be too optimistic regarding the effect that muzzle velocity has on stability. Gain twist is a recurring fad. to WinGyro's results. one needs to increase the spin to compensate. Ideally, the bullet's axis A Stability Factor of S = 1 is "marginal" where the bullet is verging on being unstable, so a Stability Factor of 1.5 is reckoned to be a good working value to ensure stability at low temperatures or high atmospheric pressures when the air density is high. Howell feels one can overstablize a bullet. With the actual OAL of 53gr V-Max including the polymer tip (.833"), it says this bullet … C.E. W.C. Davis notes that the rotational energy of a bullet is a tiny fraction quantify such overstabilization. It was later improved by William Davis Jr. of Tioga Engineering and the claim was an accuracy of 5% for super and subsonic velocities, and 10% for trans-sonic velocities. Thank you. calculations to that of Greenhill's equation) sometimes gives a better match speed. Basically like a ballistic calculator but input your barrel twist rate and it will tell you about a particular bullet stability coming out of your barrel. In comparing Hey all, I'm trying to use the Twist Rate Calculator to determine the highest BC bullet I can shoot in my 1:12 Howa .223. (published in 1929 in Britain) are notable. offers a free Win32 executable, WinGyro, which provides a much more Using the program Try to fill in as many of the bullet dimensions as possible, even if the value is zero, as in the boat-tail length for flat based bullets. with the SG correction quoted by Howell. Ballistic Trajectory Calculator. If you do not have a Shooting Chronograph, I strongly suggest you purchase one. 1879. Further, Do NOT assume from these graphs that they show the twist required to keep the bullet stable as its velocity reduces down range, or (for the second graph) the stability factor of the bullet as its velocity reduces down range. shown this older equation to not be accurate over the full range of Rifle Twist. reasonable change in rifling twist upon pressure can be ignored.". The outputs of the program are graphs of required barrel twist for a Stability Factor S = 1.5 -vs- muzzle velocity and the Stability Factor produced by a barrel of a given twist -vs- muzzle velocity.
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