JWE
Posts: 6580
Joined: 7/19/2005 Status: offline
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Ok, then did the 6.1"/60. Ran the numbers against ordinary everyday 1937 vintage Class A, with FaceHD68, just like before, and got the same numbers as before. Then ran the numbers with NaAB, against ordinary everyday 1937 vintage Class A, and got penetration values considerably "less" than mine. Woof!!, says I. What the hey, Batman? (btw, "everything" is at N1-Eff NL, FaceHD68; Full Pen, NaAB. They are equivalent.) Then I went to my trusty Lacroix & Wells, page 462, Table 9-7 and got some published numbers. They say 108mm at 15km and 100mm at 10km. No way I believe 4 inches at 22k yds, but 4.2 inches at 16k yds doesn't sound too bad. Then noticed the pen value was against NVNC, so I shot the little swine against some New Vickers with NaAB. It was a quickie, so I only got a few values, but enough, I think. Better, but still no cigar with respect to L&W. So then I shot the little swine against some New Vickers with FaceHD68, and got values that come much closer to the L&W values. So, comparing apples, to apples, to apples, it looks like the values I plotted originally are pretty darn good, if not more complimentary to the Japanese 6.1/60. If I plotted the NaAB values, the penetrations would fall much farther below the 6"/47 than I show in the plot. It's very hard to verify models without real world data, and there isn't a whole bunch of that for the 6.1"/60. But I am heartened that my ballistics output and FaceHD68 give the best agreement with what little there is available. I did find what I might consider a technical blivet in the NaAB program, for this gun. The program gives a BC of 5.33. The shell has a sectional density of 3.31, which suggests a form coefficient of 1.62, but this value is in the G5 realm (boat tail, 6crh, tangent). A better form coefficient might be from 1.8 to 1.9, in the G6 realm (flat base, 6crh, secant). That would give the little swine a BC of between 5.96 and 6.29. But then, NaAB calculates everything on a single drag model. If you click between the G5 and G6 drag plots (in NaAB), you'll see exactly why and how I got the better striking angles and velocities (and thus, penetration) for the Japanese gun. Woof !! This is so cool !! Thanks for digging deep, Juan !! Looking forward to hearing more.
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