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#1424411 - 11/06/09 08:30 AM BC VS speed question
pd721el Offline
Sergeant

Registered: 09/22/08
Posts: 175
Loc: South East SD
Newby with a question. TIA I have been playing around on JBM lately and would like to know if there is a general rule as to how much additional velocity is need to over come say a .100 lower BC when comparing two bullets out of the same gun? Or the other way around if that is how it works out. I hope this makes sence.

Example 260 remington shooting a 140 berger VLD (BC .612) at 2700 Fps, drops 274" at 1000 or you shoot a 120 Ballistic Tip (BC .458) at XXXX Fps to have equal drop? The 120 has a .154 lower BC.
Thanks Eric
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#1424477 - 11/06/09 09:10 AM Re: BC VS speed question [Re: pd721el]
kombayotch Offline
Gunnery Sergeant

Registered: 09/20/07
Posts: 1522
An equation could be derived for it and used in an Excel spreadsheet. The question is what are you trying to match? It appears that you are focused on drop. You could match wind drift. Drop is easier to compensate for than wind drift (in practice).

Often, when you match two bullets for drop, the ligher one still loses out in wind drift.

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#1424502 - 11/06/09 09:33 AM Re: BC VS speed question [Re: kombayotch]
BOLTRIPPER Offline
Super Bagman

Registered: 09/25/01
Posts: 13181
Loc: Dallas Texas USA
keep in mind...the BC degrades as the projo flys....and of course what kombayotch says

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#1424540 - 11/06/09 09:55 AM Re: BC VS speed question [Re: BOLTRIPPER]
MontanaMarine Offline
General Nuisance

Registered: 12/09/01
Posts: 5759
Loc: Canyon Ferry, MT
Depending on the bullet, sometimes BC degrades as velocity drops, sometimes it improves (according to my Sierra load manual anyways).
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#1424565 - 11/06/09 10:14 AM Re: BC VS speed question [Re: MontanaMarine]
The Mechanic Offline
General Nuisance

Registered: 09/09/06
Posts: 5104
Loc: San Diego County Ca.
Triggerfiftys data also shows the up and down BC based on velocity all the way through transonic. His data is spot on. But you would have to figure it would be as it was Doppler data.
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#1424579 - 11/06/09 10:24 AM Re: BC VS speed question [Re: The Mechanic]
Grump Offline
Gunnery Sergeant

Registered: 10/23/08
Posts: 1054
Loc: So. Utah
This tends to be distance-specific.

Match drop for 500 and the slower, higher-BC bullet still hits higher at 1,000.
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#1424635 - 11/06/09 11:16 AM Re: BC VS speed question [Re: Grump]
kombayotch Offline
Gunnery Sergeant

Registered: 09/20/07
Posts: 1522
Yep, you definitely want to do the comparison at your maximum intended shooting distance.

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#1424907 - 11/06/09 02:52 PM Re: BC VS speed question [Re: kombayotch]
pd721el Offline
Sergeant

Registered: 09/22/08
Posts: 175
Loc: South East SD
Thanks guys
_________________________
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson


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