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Anyone ever hear of the 30 FBI ?

 
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  #22  
Old 08-09-2003, 04:30 PM
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Re: Anyone ever hear of the 30 FBI ?

If you take three bullets with the same BC fired at the same velosity in a no wind condition they will drop at the same rate....Right?
Now lets say that one of the bullets is a GS solid,one is a MK,one is a PRL and we add a constant wind,the more the marrier.Which bullet drifts more in the wind?Is wind drift figured into the BC?
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  #23  
Old 08-09-2003, 04:54 PM
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Re: Anyone ever hear of the 30 FBI ?

To make it simple. You can take a 1 inch long 30 caliber bullet and a 2 inch long bullet of the same diameter. For this example give them both the same BC and velocity. Time of flight to a given target will be the same due to the BC being the same. But, when it comes to wind the longer bullet has the potential to have a larger surface for the wind to push on. It would be the same as comparing different size sails. Obviously due to design differences the area could vary from design to design. The biggest thing to think about is with the PRL you can achieve a very high BC with a smaller bullet. This gives you the High BC and smaller cross section. Sorry if this seems convoluted, but I haven't had the chance to sleep much in the past week or so.

Vince
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  #24  
Old 08-09-2003, 06:27 PM
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Re: Anyone ever hear of the 30 FBI ?

Vince you'd too much sleep cause you got it right [img]images/icons/wink.gif[/img] [img]images/icons/grin.gif[/img]. Not got get some sleep class will continue next week.
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  #25  
Old 08-10-2003, 05:51 AM
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Re: Anyone ever hear of the 30 FBI ?

Sorry guys, if the bullets have the same BC, drop and drift are the same. Drop is a TOF issue, Drift is essentially TOF as well but is computed with a component known as lag time. That is the difference between TOF(vacuum) and actual TOF. Lag time is a measure of the effects of drag on the projectile, and thus reflects BC or Coefficient of Drag. The term 'Drift' is misleading in the context of this discussion as what is actually occurring is a deflection. If you'll work the equation a bit you'll see that the bullets are NOT drifting, and in fact resist that quite a bit. From memory, and perhaps not correct: D=wind velocity(fps)/T-Tv where Tv is vacuum time, T =actual TOF.

As to denser core materials, yes, they have a higher BC for a given length and same form, or same BC for shorter projectile. The concept has great merit for many reasons, no doubt some I haven't considered. In any case however, BC is BC, regardless of material of construction.

If you have the time, get a copy of Robert Rinkers book, "Understanding Firearm Ballistics".

[ 08-11-2003: Message edited by: MAX ]
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  #26  
Old 08-10-2003, 07:59 PM
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Re: Anyone ever hear of the 30 FBI ?

Texas, what e-mail address did you send that to? If you sent it to Nighthawk042985@aol.com I'm not going to be able to read it because I got my password stolen so anyone other than me could be reading what you sent.
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Old 08-10-2003, 08:05 PM
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Re: Anyone ever hear of the 30 FBI ?

Thats the one I sent it to. Send me one and I will reply with all the PRL info that I have.
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  #28  
Old 08-13-2003, 12:00 AM
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Re: Anyone ever hear of the 30 FBI ?

Nighthawk did you get it?
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