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How important is bc?

 
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  #1  
Old 01-31-2010, 09:40 PM
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How important is bc?

Just want to discuss bc's. At what range does bc really come into play? I know it will depend on the MV, so let's say we are running at 3000fps. Then comes the $ question....How many guys can actually shoot that far in the field? My longest game harvest is at 760 yrds. I think that puts me on the edge of bc's starting to really matter. Under 600, I'm not so sure it makes that big a difference. How far down range before a boat tail makes a difference?

Food for thought,

Steve
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  #2  
Old 01-31-2010, 11:01 PM
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Re: How important is bc?

Using same bullet weights, same velocity under the same conditions:

Discounting wind drift, BC makes little difference until you get past 300 yds. From 300 to 500 there is a noticable advantage to higher BC bullets, past 500 yds. BC becomes very important.

Try the Hornady Ballistic Calculater to get an idea of the relative benefits of higher BC bullets.

Ballistics Calculator - Hornady Manufacturing, Inc

Cheers,
Jim
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  #3  
Old 01-31-2010, 11:23 PM
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Re: How important is bc?

Steve,

You sure had to pose such a difficult question Steve. That is like someone asking you which is more important. Your heart or your brain or your blood. All three are neccesary for your life the same as accuracy, terminal effects and BC are neccesary for LRH.

You are absolutely right. If shots are 600 yards and less, the BC is one of the least of my concerns unless the wind is howling super hard but then, I have no buisness shooting in super high wind anyway. I did it once and took me 3 times to connect. This was 507 yards on a sitka blacktail in a 17 MPH wind. I thought it was less, decided it was more and let her rip. The 3rd bullet hit dead on. When the math was done in reverse, it worked out to 17-20 MPH. That is more wind than I should have responsibley been shooting in. The bullet I was using had a BC of over .6 and the wind still beat me. Had I been using a bullet with .5 for a BC, the difference would have still only been less than 5". For practical responsible wind conditions, BC is not much a deciding factor for me. I can get nearly ANY respectable bullet to arrive at 600 yards with 1800 FPS+ which most hunting bullets expand down to 1800 FPS and some will at lower velocities.

For a bullet at 2810 FPS at 600 yards with a full 10 MPH at 90 degrees, the drift is 28" using a BC of .49. If you step up to a .59 all else being equal, it is 23" for a 5" difference. This is certainly not enough of a difference (IMHO) to toss terminal performance out the window for that extra 5".

For hunting:

My number 1 priority is accuracy. My second is that it will open up on game at the range(s) I intend to shoot. The BC is the 3rd most importand factor. For example, my pet 308 load is the 168 AMAX. It is scary accurate and opens up on sheep and deer at ranges I have no buisness hunting at. The BC is decent and comes into play at some point because I do need enough velocity at the target for it to do its job. Is the BC important to me? Absolutely. Is it my #1 concern? Not at all. The wind drift at practical hunting ranges in practical winds between my 168 AMAX and the 190 VLD is very minimal.

If the senario is such that these ranges are exceded and really long shots are taken then the 308 is no longer my choice and I move to the 338 Edge and for 2 reasons. It delivers a HUGE bullet very accurately and very high BC's are simply a bi-product of the bigger 338 loads. With the combo of weight and BC, the remaining velocity and subsequent energy is devestating. This is critical when shooting in the 600-1000 yard+ zone. So in this case, even though the BC is still #3 on my priority list, it is FAR more important than when my 308 is on the loose.

So in short, I think BC is semi important for up to 600 yards and becomes very important and increasingly more important as the distance grows. That said, when it comes to my beyond 600 yard guns, if ANY of the 3 components I listed are missing, another bullet will be tested untill I find one that has all 3.

For F-Class:

#1 is accuracy. #2 is BC. Hopefully I can find the most accurate load(s) with VERY high BC's. F-Class X-Rings around here are small (1/2 MOA) and want as much forgivness as possible where if I am shooting at a big game critter, the kill zone is bigger and I can live with a wee bit less forgivness in lieu of terminal performance.

Many will contend that BC is #1 as it helps deliver the bullet with more energy and subsequent terminal effects and that IS true. However true it is, it doesnt equate to terminal performance if the load is not accurate enough to connect. Some others may contend that high BC bullets make for more accuracy in windy conditions as they are more forgiving with a minor amount of error on the shooter's part. Again, I cannot argue that point. Still yet, you need an accurate baseline in the first place to take advantage of the forgivness. Accuracy, terminal, BC in that order. It should be noted that accuracy and terminal effects in my mind are so close on the priority list that they are dang near equal. BC is a close third albiet it is third.


M
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Last edited by Michael Eichele; 01-31-2010 at 11:36 PM.
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Old 01-31-2010, 11:55 PM
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Re: How important is bc?

I ran some arbitrary #'s. A .338 250g with bc of .638 and .438 @ 3000fps. All else equal. At 600yrds there is a 9" difference in wind drift @ 10mph full value wind. 16" vs 25". Now in my mind this is a huge difference in bc. But in reality not a huge difference in drift.

I started this thread in light of some of the recent bickering about bc's. And my thought was basically the same as Michael's. I look at the bc of a bullet as a potential bonus.

I would like to hear from others on this, so keep it coming.

Steve
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Old 01-31-2010, 11:56 PM
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Re: How important is bc?

Quote:
Originally Posted by RockyMtnMT View Post
Just want to discuss bc's. At what range does bc really come into play? I know it will depend on the MV, so let's say we are running at 3000fps. Then comes the $ question....How many guys can actually shoot that far in the field? My longest game harvest is at 760 yrds. I think that puts me on the edge of bc's starting to really matter. Under 600, I'm not so sure it makes that big a difference. How far down range before a boat tail makes a difference?

Food for thought,

Steve
Actually, a boattail doesn't make that much difference until you reach subsonic which is WAY out there, depending on B.C. of course.....
Rich
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  #6  
Old 02-01-2010, 12:11 AM
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Re: How important is bc?

0.200 difference in BC is a pretty large jump there Steve!
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  #7  
Old 02-01-2010, 01:06 AM
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Re: How important is bc?

Steve,

Good question and it's all relative to what's important to the shooter and what he is willing to pay. If 600 yds is all the farther you're going to shoot, then it just doesn't matter a whole lot.

For me, since becomimg interested in LRH, I've come across some good ambush spots that are in excess of 1K. Last year I found a good spring bear ambush spot in the range of 1000-1300 yds across a canyon. I'm hoping to get a shot there this year. In this case BC is very critical and every littel bit helps. It extends my max effective range and It helps buck wind.

The difference out of my RUM for a .5, .55 and .6 BC 180 gr @ 3400 fps bullet means ranges of 1100, 1225, and 1325. A BC of .7 gets my bullet on target with a good bit more thump and a significant diff in wind drift. The diff in wind drift between .5 and .7 @ 1200 yds is about 55%, 78" vs 50" per 10 mph.

Bottom line is it's all relative based on a person's goals and priorites. Ask 10 different people and you'll get 10 different answers.

-Mark
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