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Ballistic Coefficient

 
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  #1  
Old 08-03-2005, 01:06 AM
daveosok
 
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Ballistic Coefficient

<font class="small">Code:</font><hr /><pre>Geschätzter Cw-Wert, BC und Stabilität, Standard ICAO Amosphäre, Meereshöhe

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Möller KWJG Cal. 7.620 mm (.308), 11.0 g 169.75 grain

Ballistischer Koeffizient für die Luftwiderstandsfunktion G1

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Geschwindigkeit Lufwiderstandsbei- Drehzahl, gyro. Maximale Drall-

wert, Formfaktor Stabilität länge

und BC Drall 32,5 Kal. für s = 1.3

Mach m/s fps Cw i BC UPM s Kal. in. mm

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0,441 150 492 0,066 0,321 0,796 35433 0,81 25,7 7,9 201

0,514 175 574 0,064 0,322 0,794 41339 0,80 25,4 7,8 199

0,588 200 656 0,064 0,320 0,800 47244 0,78 25,1 7,7 196

0,661 225 738 0,064 0,310 0,825 53150 0,75 24,6 7,6 193

0,735 250 820 0,064 0,288 0,888 59055 0,71 24,0 7,4 187

0,808 275 902 0,065 0,254 1,007 64961 0,65 22,9 7,1 179

0,882 300 984 0,073 0,230 1,112 70866 0,55 21,2 6,5 166

<font color="red">0,955 325 1066 0,147 0,357 0,717 76772 0,37 17,4 5,3 136

1,000 340 1116 0,367 0,776 0,330 80384 0,47 19,6 6,0 153

1,102 375 1230 0,131 0,225 1,135 88583 0,56 21,2 6,5 166</font>

1,175 400 1312 0,299 0,482 0,531 94488 0,65 22,9 7,0 179

1,763 600 1969 0,291 0,471 0,543 141732 1,03 28,9 8,9 226

2,351 800 2625 0,240 0,440 0,581 188976 1,17 30,8 9,5 241

<font color="green">2,939 1000 3281 0,204 0,402 0,637 236220 1,25 31,8 9,8 249</font>

3,526 1200 3937 0,178 0,358 0,715 283465 1,29 32,4 10,0 253

4,114 1400 4593 0,157 0,319 0,801 330709 1,33 32,8 10,1 257

4,702 1600 5249 0,142 0,288 0,889 377953 1,35 33,1 10,2 259

5,290 1800 5906 0,129 0,263 0,974 425197 1,38 33,4 10,3 261

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</pre><hr />

This was sent to me by a gentelmen whos name is Lutz Moeller.. He is a ballastician and has phd's and all that stuff required of someone who has published works in the scientific world.
One thing I found very interesting was how the bc changed as the speed changed, I knew it did that but not to the degree that it has changed in the above chart. It is also interesting to note that at 1116 fps roughly the speed of sound you can see a dramatic decrease in BC and this is where your transonic stage is. I heard folks talking about this and knew it to be true but here is first hand how drastic the change is and why stability suffers greatly when entering this transonic stage.
It was surprising to me that at 984 fps the BC was 1.112 exteremely high and subsonic which shows the relationship. I suppose this is why the 30 Whisper is so effective as a subsonic cartridge. Here is the bullet in question

One really neat thing was the transition from sub to super and the bc at that point in time.
This is all mathematical of course but the information contains some very interesting data which is very close I guess being his background and all. You can find trajectory programs on his site too.
Notice where the bc is for fps that most of the big mangums are capable of firing at(in green).
Notice also that the G function is a G1. Youd have to email this guy to understand what hes all about. When he called me a lot of what he was talking about went completely over my head and was no doubt a intelletual of genius proportions.
Leave it to the Germans for such work.
Well this was not intended to stir any pots just some really neat work by a very friendly guy who by the way also sent me free from Germany the above bullet about 50 or so they are all pulled military bullets ande the tips are a little messed up. Nothing a metplat trimmer wont clean up.
I am not intending to start anything here just thought yall might like to see some work from a ballistician.
Dave
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  #2  
Old 08-05-2005, 01:32 PM
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Join Date: Feb 2004
Location: Pennsyltucky
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Re: Ballistic Coefficient

not quite on the subject but i wish we could get someone "over here" to make this banded style of bullet.looks to be along the lines of the gs customs.notice the ever so slight chamfer to make it a boat tail but not exactly a rebated boattail.my understanding of this style of bullet is you can shoot many,many, rounds through it and not wear out the throat.even with very overbore cartridges.
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  #3  
Old 08-05-2005, 03:37 PM
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Join Date: Sep 2004
Location: Nevada
Posts: 564
Re: Ballistic Coefficient

The Germans studdied projectiles way before WWII with high speed photography. They were the first to fire rounds in the 5000 FPS range. That's why tanks or field guns with the 88mm were so deadly at extreeme ranges.

Back to the sugject. The mach to sub mach is why bench rest shooters choose bullet weight and velocities which will keep them out of the trouble area or use bullets of long lengths that have recorrection factors after the transition.
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