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| one of us |
Ray, I did that in my first post: "If you are building a rifle, go with the tightest twist you can get." Your facts are based on the Greenhill method and are wrong. Not your fault, as I pointed out. My opinions and theories are based on the work of Bob McCoy and others and based on the latest information - well, at least the previous century and not the 1800s. 30 Years of designing and making bullets may also have something to do with my opinions and theories. To get the right numbers for the NPT and Barnes bullets, go to the links I gave or download McGyro and go to work. It would be better that you do it yourself. You do not believe what I post and, in any case, I have no interest in the bullets you want to use. I would use something else (but of course I am wildly biased).  | |||
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It's a wonder the 9.3x62 in it's original, " stock--out the box- slow twist rate" and the 9.3 x64 ever got to kill anything ? Perhaps they, and those who owned and hunted with them never got the memo ? They need fast twist barrels and super bullets to make em work? So if there is anyone out there with a 1:14 9.3x62 or 9.3x64 please let me know I will gladly take them off your hands, especially if it's a old Mauser or better yet and genuine long octagonal barrelled Brennecke  | |||
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That is as hackneyed a statement as "you can load it again", "during which part of the animal's death did the bullet fail" and "animals don't read tables". Come on Alf, don't play dumb. | |||
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Ok Gerard, Let's try this again. Don't put words in my mouth - I never said I disagreed with anything. Even offered to truly listen if you would show us the difference between the various formulas you linked. Whether you recognize it or not - You come across as just "lobbing shots over the bow" but provide no substance and deflect reasonable requests. All I asked was that you demonstrate your knowledge of both formulas and provide an example showing that there is a practical difference for picking a 9.3 barrel twist so that we could come away with some new knowledge from this thread. So far you seem like a child that has found a new toy and wants to show it everyone but really does know how it works, much less explain it to others. ________ Ray | |||
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Hello Ray,
Classic Greenhill: T' = 150 / L' Modified Greenhill: T = 150 * D^2 / L Bowman: T = 3.5 * V^0.5 * D^2 / L Since then Don Miller has done variants of the modified Greenhill such as the Miller formula below: Sg=(30*C5)/((C7/C4)^2*C4^3*C6/C4*(1+(C6/C4)^2))*(C8/2800)^(1/3)*((C9+460)/(59+460)*29.92/C10) All of these are inadequate. An entry level system to use is McGyro or one of the calculators at JBM Ballistics or Border Barrels. Both are based on McGyro below. McGyro: 10 REM MCGYRO, APRIL 1986, BY R. L. MCCOY. 20 REM ESTIMATE OF GYROSCOPIC STABILITY FACTOR (SG) 30 REM FOR A UNIFORM DENSITY PROJECTILE. USES THE 40 REM MCDRAG INPUT FORMAT, WITH TWO ADDITIONAL QUANTITIES; 50 REM PROJECTILE DENSITY (GRAMS/CC), AND RIFLING TWIST 60 REM RATE (CALIBERS/TURN). OUTPUT IS ECHO OF INPUT 70 REM FOLLOWED BY A TABLE OF LAUNCH MACH NUMBER, LAUNCH 80 REM GYROSCOPIC STABILITY FACTOR, AND RIFLING TWIST RATE 90 REM REQUIRED TO GIVE SG=1.5 (SLOWEST ACCEPTABLE TWIST RATE). 100 REM 110 REM THE STANDARD DEVIATION OF THE SG ESTIMATE IS 120 REM 5 PERCENT AT SUBSONIC AND SUPERSONIC SPEEDS, AND 130 REM 10 PERCENT AT TRANSONIC SPEEDS. 150 CLS 160 KEY OFF 170 COLOR 7, 1, 8: CLS 180 KEY ON 190 DIM M(22), N15(22), S6(22) 200 REM 210 REM define table of launch mach numbers 220 REM 230 DATA 0.5,0.6,0.7,0.8,0.9,0.95 240 DATA 1.0,1.1,1.2,1.3,1.4,1.5 250 DATA 1.6,1.7,1.8,2.0,2.2,2.5 260 DATA 3.0,3.5,4.0,5.0 270 FOR I = 1 TO 22 280 READ M(I) 290 NEXT I 300 RESTORE 310 REM input projectile dimensions 320 CLS 330 PRINT "Enter the McGyro Inputs, one quantity at a time." 340 PRINT 350 PRINT "Enter projectile reference diameter (mm):"; 360 INPUT D1 370 PRINT 380 PRINT "Enter projectile total length (Calibers):"; 390 INPUT L1 400 PRINT 410 PRINT "Enter nose length (Calibers):"; 420 INPUT L2 430 PRINT 440 PRINT "Enter RT/R (Headshape parameter):"; 450 INPUT R1 460 PRINT 470 PRINT "Enter boattail length (Calibers):"; 480 INPUT L3 490 PRINT 500 PRINT "Enter base diameter (Calibers):"; 510 INPUT D2 520 PRINT 530 PRINT "Enter meplat diameter (Calibers):"; 540 INPUT D3 550 PRINT 560 PRINT "[NOTE: Do not enter the center of gravity" 570 PRINT "location. Program assumes the center" 580 PRINT "of gravity is at the volume centroid]" 590 PRINT 600 PRINT "Enter projectile density (grams/cc):"; 610 INPUT R10 620 PRINT 630 PRINT "Enter rifling twist rate (Calibers/turn):"; 640 INPUT N 650 PRINT 660 PRINT "Enter projectile identification:"; 670 INPUT K$ 680 PRINT 690 CLS 700 PRINT "McGyro, April 1986, R. L. McCoy." 710 PRINT 720 REM echo input data 730 PRINT "Projectile Identification: "; K$ 740 PRINT 750 PRINT "DREF", "LT", "LN", "RT/R" 760 PRINT "(MM)", "(CAL)", "(CAL)" 770 PRINT D1, L1, L2, R1 780 PRINT 790 PRINT "LBT", "DB", "DM", "RHOB", "TWIST" 800 PRINT "(CAL)", "(CAL)", "(CAL)"; "(GM/CC)", "(CAL/TURN)" 810 PRINT L3, D2, D3, R10, N 820 PRINT 830 PRINT " LAUNCH", "LAUNCH", " N" 840 PRINT "MACH NO."; SG; ","; (SG = 1.5); "" 850 PRINT 860 S1 = SQR(1 - D3) 870 S2 = 1 - D2 ^ 2 880 FOR I = 1 TO 22 890 IF M(I) <= .95 THEN 930 900 IF M(I) >= 1.1 THEN 950 910 G1 = 71.73001 - 42.433 * M(I) 920 GOTO 960 930 G1 = 20.082 + 3.726 * (M(I) / SQR(1 - M(I) ^ 2)) 940 GOTO 960 950 G1 = 35.079 - 24.066 * (SQR(M(I) ^ 2 - 1) / M(I)) 960 A1 = G1 * S2 970 IF M(I) < 1 THEN 990 980 IF M(I) >= 1 THEN 1030 990 B1 = SQR(1 - M(I) ^ 2) 1000 B = .82112 + .36971 * B1 1010 A = 34.779 + (24.091 + (8.977 - 12.804 * R1 + 8.38 * R1 ^ 2) * L2) * S1 * B1 - A1 1020 GOTO 1060 1030 B1 = SQR(M(I) ^ 2 - 1) / M(I) 1040 B = 1.0528 + .23379 * B1 - .004884 * (M(I) - 1) 1050 A = 58.873 + (8.115 + (14.15 - 15.348 * R1 + 7.216 * R1 ^ 2) * L2) * S1 * B1 ^ 2 - A1 1060 N15(I) = (A * SQR(R10)) / (L1 ^ B) 1070 S6(I) = 1.5 * ((N15(I)) / N) ^ 2 1080 NEXT I 1090 REM Print McGyro Output 1100 U$ = " #.## ##.## ###.##" 1110 FOR I = 1 TO 22 1120 PRINT USING U$; M(I); S6(I); N15(I) 1130 NEXT I 1140 PRINT 1150 PRINT 1160 PRINT "Copy this? (Enter Y for Yes, N for No):"; 1170 INPUT K2$ 1180 IF K2$ = "N" THEN 1410 1190 LPRINT 1200 LPRINT 1210 LPRINT "McGryo, April 1986, R. L. McCoy." 1220 LPRINT 1230 LPRINT "PROJECTILE IDENTIFICATION: "; K$ 1240 LPRINT 1250 LPRINT "DREF", "LT", "LN", "RT/R" 1260 LPRINT "(MM)", "(CAL)", "(CAL)" 1270 LPRINT D1, L1, L2, R1 1280 LPRINT 1290 LPRINT "LBT", "DB", "DM", "RHOB", "TWIST" 1300 LPRINT "(CAL)", "(CAL)", "(CAL)", "(GM/CC)", "(CAL/TURN)" 1310 LPRINT L3, D2, D3, R10, N 1320 LPRINT 1330 LPRINT "MACH NO.", " SG", "(SG=1.5)" 1350 LPRINT 1360 FOR I = 1 TO 22 1370 LPRINT USING U$; M(I); S6(I); N15(I) 1380 NEXT I 1390 LPRINT 1400 LPRINT 1410 REM CHECK FOR ANOTHER CASE 1420 PRINT 1430 PRINT 1440 PRINT "Run another case" 1450 PRINT "Enter Y for Yes, N for No:"; 1460 INPUT K1$ 1470 IF K1$ = "Y" THEN 310 1480 END New toy. That is funny. See this post dating back six years. | |||
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LOL - If that's how you explain it, I now understand why you’re so frustrated. ________ Ray | |||
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"[/QUOTE]It is not an argument or a debatable matter, it is fact, proven many times over. [/QUOTE] Sure, and for centuries it was a proved fact that the sun, moon, and planets revolved around the earth. Mathematical formulae existed which could predict the movements of all of them, usually with great accuracy. The only problem was, the formulae had all been developed to deal with movements based on a false asumption. So every time the predictions didn't work, another "sub-formula" had to be developed and added to the mix, until the whole matter was so complex as to be in some ways useless. It confused, rather than simplified understanding. The same MAY be occuring in the field of ballistics, especially by those who criticize Greenhill's work. That is exactly why I didn't want to debate this with you or anyone else who has a "bought into" mind set about it, now or ever, as I said earlier. To go farther can test our most basic physics and associated ballistic assumptions. Your statement about static stability shows you believe the important thing is spin related to distance travelled. That may be useful for relatively crude calculations, but it may be an incorrect assumption. For one thing, it shows bullets becoming more stable as they travel farther, but "more stable" only in terms of more revolutions per foot or other unit of distance travelled. Viewed from another perspective, the important thing may be the rate of spin per unit of time, and in that sense, stability decreases as flight time increases and spin decreases. To really get into it, we would have to go into subnanophysics, and this is not the place to do that. Why subnanophysics?....because the farther we go in that field, the more we realize that mass and energy are two ways of looking at the same thing. Einstein was one of the first who realized that mass, energy, AND TIME may be THREE ways of looking at the same thing....that is, three facets of the same thing. And in there lies the reasons a "rotation relative to time" computation may be a simpler (better?)way to look at bullet stability than just postulating a spin vs. distance approach. No one here wants to see us get into that. Especially not me, as it is hard to discuss things open mindedly when any one of the researchers is already a "true believer" in the status quo of science. So I will end my part in the theoretical aspect of this. As to twist rate for rhe 9.3x64, I would choose a 1-in-11" twist if that was available. As I don't think it is handily available, I'd go with a 1-in-12" twist. | |||
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I hear you about new theories. How do you fit this into the new theory: "Therefore, when launched at 1200fps and checked at 25, 50 and 100m, it is tumbling end over end. The same bullet, when launched at 3000fps, goes through the transonic to subsonic (1200fps to 1000fps) with some yawing but no tumbling." | |||
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forrest, i have used 1x14 lw barrels in all my 9.3x62 & 64s and they all shot tiny groups with 250 to 320 gr bullets..excuse my typing as tore up my rt. hand roping, and scheduled for surgery, not a goog lefty.. that said, if you don't use that bsrrel iwill purchase it from you if yhat will help, i can aleays use lw barrel. Ray Atkinson Atkinson Hunting Adventures 10 Ward Lane, Filer, Idaho, 83328 208-731-4120 rayatkinsonhunting@gmail.com | |||
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Dang Ray, that's your idea of resting up for the winter?  Aut vincere aut mori | |||
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zir, it's the pitts..can't rope and that is the worst part; have to shoot left handed; had to farm out the last part of my chechering and that costs, doing your daily constitional is tricky to say the least,...told the doc to fix it or cut the danm shooting finger off, and let me get back to doing what i like, ican make it work with 4.  Ray Atkinson Atkinson Hunting Adventures 10 Ward Lane, Filer, Idaho, 83328 208-731-4120 rayatkinsonhunting@gmail.com | |||
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