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How important is bc?

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  #22  
Unread 02-01-2010, 03:38 PM
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Re: How important is bc?

Quote:
Originally Posted by bsl135 View Post
I'd like to answer the question from a slightly different perspective.
Good stuff. I'll also add another perspective into the mix people don't think about much (but should). Higher BC bullets are less sensitive to changes in weather.

Much like wind drift, for any given temp or pressure change, the error will be less with the higher BC bullet. Or looked at another way, the higher BC the bullet you use and the faster you shoot it the farther you can go with simple drop charts before needing to worry about weather changes.

If using a PDA for every shot it's not that big a deal, but understanding when you actually need to use a PDA and when you don't is something people should know. That distance being farther increases the odds when speed is needed in the field.
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  •   #23  
    Unread 02-01-2010, 06:20 PM
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    Re: How important is bc?

    [QUOTE]
    Quote:
    Originally Posted by RockyMtnMT View Post
    You are correct. Can you shoot a one shot kill at 1100 yards in a 10 mph variable wind with any bullet? Be honest.
    Yup, I sure can - do it all the time OK, serious.... no, I would not take a 1000 shot on a game animal in a 10 mph wind (except maybe a speed goat). If I knew for sure it was a 10 mph wind, then yes I would because it could be accurately corrected for. It's not the amount of wind, it's the ability to accurately dope the wind. Which, as already mentioned, is where a higher BC helps to enlarge the degree of forgiveness. If I was antelope hunting @ 4000' elevation, with previously mentioned .5 vs .7 BC loads and had an 800 yd shot in an estimated 10 mph wind, a 3 mph estimation error would result in a 7" POI error for the .7 BC vs a 10 1/2" POI error for the .5 BC load. And yes, there is a big diff between .5 and .7 BC, bit that's what LR is all about. That's why all the interest in the high BC wildcat and custom bullets. That's why LR shooters are willing to pay up to 4x as much for them as standard bullets. I better stop there

    Another big factor is that each increase of .5 BC gains about 100 yds effective range. Going from .5 BC to .7 BC in the above example takes you from 1000 yds to 1400 yds. I think that's very significant. And here again is where individual goals and priorites come in. Some guys just dont care to shoot past 600 or 800 or whatever. Other guys want to shoot as far as they can. To the later, BC is extremely important.
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      #24  
    Unread 02-01-2010, 07:39 PM
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    Re: How important is bc?

    [QUOTE=MontanaRifleman;357122]
    Quote:

    Yup, I sure can - do it all the time OK, serious.... no, I would not take a 1000 shot on a game animal in a 10 mph wind (except maybe a speed goat). If I knew for sure it was a 10 mph wind, then yes I would because it could be accurately corrected for. It's not the amount of wind, it's the ability to accurately dope the wind. Which, as already mentioned, is where a higher BC helps to enlarge the degree of forgiveness. If I was antelope hunting @ 4000' elevation, with previously mentioned .5 vs .7 BC loads and had an 800 yd shot in an estimated 10 mph wind, a 3 mph estimation error would result in a 7" POI error for the .7 BC vs a 10 1/2" POI error for the .5 BC load. And yes, there is a big diff between .5 and .7 BC, bit that's what LR is all about. That's why all the interest in the high BC wildcat and custom bullets. That's why LR shooters are willing to pay up to 4x as much for them as standard bullets. I better stop there

    Another big factor is that each increase of .5 BC gains about 100 yds effective range. Going from .5 BC to .7 BC in the above example takes you from 1000 yds to 1400 yds. I think that's very significant. And here again is where individual goals and priorites come in. Some guys just dont care to shoot past 600 or 800 or whatever. Other guys want to shoot as far as they can. To the later, BC is extremely important.
    AMEN!!
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      #25  
    Unread 02-01-2010, 08:00 PM
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    Re: How important is bc?

    [QUOTE=MontanaRifleman;357122]
    Quote:

    Yup, I sure can - do it all the time OK, serious.... no, I would not take a 1000 shot on a game animal in a 10 mph wind (except maybe a speed goat). If I knew for sure it was a 10 mph wind, then yes I would because it could be accurately corrected for. It's not the amount of wind, it's the ability to accurately dope the wind. Which, as already mentioned, is where a higher BC helps to enlarge the degree of forgiveness. If I was antelope hunting @ 4000' elevation, with previously mentioned .5 vs .7 BC loads and had an 800 yd shot in an estimated 10 mph wind, a 3 mph estimation error would result in a 7" POI error for the .7 BC vs a 10 1/2" POI error for the .5 BC load. And yes, there is a big diff between .5 and .7 BC, bit that's what LR is all about. That's why all the interest in the high BC wildcat and custom bullets. That's why LR shooters are willing to pay up to 4x as much for them as standard bullets. I better stop there

    Another big factor is that each increase of .5 BC gains about 100 yds effective range. Going from .5 BC to .7 BC in the above example takes you from 1000 yds to 1400 yds. I think that's very significant. And here again is where individual goals and priorites come in. Some guys just dont care to shoot past 600 or 800 or whatever. Other guys want to shoot as far as they can. To the later, BC is extremely important.
    So a .5 to .7 bc change makes a 3.5 inch difference in POI at 1000yrds when there is an error of 3mph in the wind judgment. Not much for such a large difference in bc. And again we are talking about a shot that most of us long range hunters are not willing to take on a game animal. If I knew the wind was steady, no sweat. But that just isn't how it works.

    It goes back to my original post. I'm not sure that it makes a big enough difference to worry 'much' about. More realistic difference, in bc, to look at is .1. Then the difference becomes much less at 1000 yrds.

    Steve
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      #26  
    Unread 02-01-2010, 08:08 PM
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    Re: How important is bc?

    Quote:
    Originally Posted by bsl135 View Post
    The boat tail increases BC, which reduces both drop and wind deflection.

    How much of an effect the boat tail has depends on it's length and angle. Also remember that the boat tail reduces the bearing surface length compared to a similar weight flat base bullet. The reduction in in-bore friction can mean higher MV.

    -Bryan
    So, does the boat tail help with wind deflection by reducing the time of flight? I apologize for the simpleton questions, I'm a little thick in the head. I'm having trouble visualizing how a boat tail reduces wind drift.

    Thanks for your patience,
    Steve
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      #27  
    Unread 02-01-2010, 08:12 PM
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    Re: How important is bc?

    Quote:
    Originally Posted by RockyMtnMT View Post
    So, does the boat tail help with wind deflection by reducing the time of flight?
    Yes.

    Fitch
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      #28  
    Unread 02-01-2010, 08:27 PM
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    Re: How important is bc?

    Quote:
    Originally Posted by Fitch View Post
    Yes.

    Fitch
    So, two bullets, all things being equal, other than the boat tail. Time of flight to a thousand yards is .2 seconds different. How much wind drift difference does that make?

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