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ballistic coefficient questions . 6.5 mm bullets

 
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  #92  
Old 01-19-2013, 06:46 AM
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Re: ballistic coefficient questions . 6.5 mm bullets

It seems the German's and Sweede's had the moderate velocity 6.5 twist rate figured out a long time ago. 1 in 7.7 .
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  #93  
Old 01-19-2013, 08:25 AM
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Re: ballistic coefficient questions . 6.5 mm bullets

Quote:
Originally Posted by MontanaRifleman View Post
.4 vs .8 was just a hypothetical example. If I don't get the significant difference in accuracy, I would weight the cost of the bullets a lot more. I have only shot them, 180 STD, for initial load development in my 300 RUM and they showed excellent accuracy. They showed about 50 fps better velocity than 180 E-Tips. Yes, I go straight to best powder and charge results. No seating trials. They do not have a traditional ogive that engages the lands. The bore rider is ideally seated into the lands with the driving band and sealtite band right behind.

I have a 6.5 WSM in the work and Outlaw has already used the 6.5 130's in his WSM with good results. With an overbore like the 6.5 WSM, you don't want to spend a lot of time finding the right bullet, the right powder and the right seating depth. My plan is to develop 1 load for the CE's for hunting and another load with maybe Bergers for other shooting.

Yup, I read LTLR's thread and liked what I read which confirms my limited experience with them.
Thank you! That is all good information to know. Now I'm amped up about starting load development for my .375 when I get home. I can't wait!
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  #94  
Old 02-10-2015, 09:28 AM
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Re: ballistic coefficient questions . 6.5 mm bullets

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Originally Posted by MontanaRifleman View Post
Most manufacturers do overstate their bullet's BC's. Bryan Litz has tested many of the popular bullets and printed the results in his books, Applied Ballists. In the first volume he lists the 130 Scirocco with a G1 BC of .491 averaged from 3000 to 1500 fps.
I apologize for resurrecting an old thread but I thought this might notify the posters here. I'm specifically looking for the Scirocco II and the real world BC in Bryan's book. Does anyone have the second edition or know if the above info is for the original Scirocco or the II? I'm shooting this bullet at 3250 at 6000 feet. I know Swift tests their BC at 100 yards. At least they did when they ran a test for me.

At 700 yards, the difference between the published .571 and the .491 quoted above is 4 inches.
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  #95  
Old 02-10-2015, 07:27 PM
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Re: ballistic coefficient questions . 6.5 mm bullets

The .491 is a logical average falling from 3kfps MV, probably under ICAO conditions(SL, 29.92"Hg, 59deg).
Now add std conditions at 6000ft(38deg, 24"Hg), the same bullet goes to .587 and another 250fps beginning adds ~.007, so you're looking at .594 for a local BC.

Be sure to test it
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  #96  
Old 02-10-2015, 08:32 PM
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Re: ballistic coefficient questions . 6.5 mm bullets

Thanks Mike. Do you know if the bullet in the book is the original Scirocco or the Scirocco II?
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  #97  
Old 02-10-2015, 08:59 PM
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Re: ballistic coefficient questions . 6.5 mm bullets

That distinction is not made in the 2nd edition book. So I don't know.
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  #98  
Old 02-14-2015, 10:42 PM
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Re: ballistic coefficient questions . 6.5 mm bullets

I think the Scirocco II was out before the 2nd edition so I'd guess it's the II in his book.

That Puts the Scirocco down around the 130 Accubond with 488 although I'd guess that is actually lower as well. Is the 130 Accubond in Brian's book as well?
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