Ballistic Coefficient (BC) - How important is it?

[BrentM]

Mountain wind is awful. I deal with terrain based wind every time I'm out. I'll take any advantage I can get. Reading wind in the winter when things are frozen is not easy.

 

[HARPERC]

.....Try this same exercise with the lower bc bullet being 20g lighter thus running 200 fps faster. This would be a good comparison of two bullets with similar form factor but the lighter one having less bc because of the weight. This sets up the rabbit and turtle race. Turtle always wins but in many cases he doesn't pass the rabbit until further down range than is needed..........

I think 200 fps doesn't represent well what some of us are looking at. Some of the bigger case driving bullets several hundred fps are beginning to be realistic. Using the generic Nosler data in .338 RUM, The 180 Accubond at 3535 fps (BC 0.372) vs the 300 grain version at 2643 fps for example (BC 0.72) Using generally 1800 fps as a threshold for good expansion gets both to 700 yards, before the 300 starts its run to the 100 yard line. The 300 is at 1554 fps while the 180 is at 1314. Drop favors the 180 all along the way-256" against 319" at a 1000. Drift goes to the 300 in a 10 mph wind 61" to 99" at a 1000.

With no surprise in that caliber the 250 grain makes a good case for itself.

I won't argue wind calls aren't important, but terminal performance is paramount. One can always pass secondary to conditions, I passed up a 300 yard shot on a goat due to conditions. Once it's turned loose the bullet has to perform.

BC important YES! However, there can be more than one way to skin a cat, all of them easier when the cat is dead.

 

[bigngreen]

All these things need to be balanced ideally IMO but we are all in different situations, for me I don't worry about close range performance as much because it's close, I'm not worried about getting into a shoulder or missing because were going sub inch in range it might be an issue, I make decisions based on performance in the 600-1000 yard range on most guns and some in the 1400-1600 yard range for others. I've done the running lighter bullets at warp speed and it did not fit me well, I shoot to much and to far for it to work out, so I care more about BC than speed, I'd rather shoot a 215 gr Berger from a 308 than a 165 gr bullet from a 300 RUM!!

 

[HARPERC]

All these things need to be balanced ideally IMO......but we are all in different situation....... I'm not worried about getting into a shoulder or missing because were going sub inch in range it might be an issue........

Sub MOA is another factor if the wheels fall off because we're driving it too hard that's not good either. Choice in the end is made up of assembling all the parameters.

 

[WildRose]

I mean technically a cartridge will produce the velocity of the bullet and bullet Mach determines BC so...

Bullet weight, diameter, and form factor play a big part in that equation as well.

 

[gohring3006]

Every scenario I input at long range, the high bc bullets always gives a better hit percentage. Sometimes not much more, but it's always there

 

[rustyshackleford]

Picky, picky, picky!
Guys, I was comparing two SIMILAR cartridges with two bullets of very different BCs. (i.e. nearly similar bullet weights and similar design)
Yes, I know we're talking bullets and not cartridges. Just using two well known cartridge examples. And we know most competitive PRS shooters no longer use .308 Win cartridges for this reason.

Eric B.

Pretty sure it's more to do with recoil, hence the increasingly smaller bores. From a 24 inch barrel I bet a Berger 200.20x could be pushed fast enough from a 308 to beat 6.5 CM. However, I KNOW which would recoil more and on the clock that matters.

 

[dfanonymous]

Todd stole that method for his own by the way. It was first presented to the Army school house in the late 90's by Dan Flowers. I learned it from Dan in 1999. Since ballistic programs weren't yet readily available to individuals, Dan worked it out using Excel spreadsheets.

Todd learned it in about 2005 or later, and took it for his own. He then monetized it by developing the Tremor reticles around it, and selling it back to the Army he stole it from.

Nice. Nothing to original about shooting techniques these days, lol

 

[LVJ76]

I see where issues like fighting the wind come into the discussion of BC and its relative importance, as discussed above. But my own consideration of BC is a little different, when considering hunting bullets and their effectiveness at a given distance.

Personally, I begin my thinking with terminal effects. There seems to be an assumption throughout this entire discussion that all bullets under consideration have equal terminal effects, so the focus is only on external ballistics (how the bullet travels from the gun to the target).

I want to know the effective velocity range for the bullets I'm considering, which means I'm concerned about velocity. BC comes into the equation because it tells me what velocity I can expect at a given distance. I know that dialing for drop is relatively easy, as has been mentioned, but it's not the drop I'm focused on. It's the velocity. The velocity at distance (the result of BC) tells me my effective range in order to achieve the terminal effects on target that I'm looking for.

Also, I agree with the notion expressed above that in comparing different bullets, you should focus on like bullets from a terminal perspective. Said another way, you should compare the actual options you would use. For example, I wouldn't compare a 180 gr lead core bullet to a 180 gr monolithic, because I wouldn't choose between those two. The monolithic will penetrate better and have similar terminal effects when using 160 or 150 grains, so that's the bullet I'd compare to the 180 gr lead bullet.

Yes, I opened the terminal effects bucket of worms. My intent is not to derail this discussion, but only to explain how I (and maybe others) incorporate BC into my thinking when considering hunting bullets and their effective range.

Agreed, it cant be just about BC's, but about how the bullet will perform on game. Especially when shots at close range come in to play.

Or you can double load. Bonded bullet first followed by a long range round like a Berger or ELD. If you are shooting at an animal at 1,000 yds most likely you'll have time to set up and load a long range round, but up close it might be a shot that you only have a few second to fire.l and BC won't matter.

I believe at 700+ yds its when BC really starts to matter, but also depends on the cartridge.

On smaller cartridges like my 7mm-08 BC does play a bigger role than my 7 Mag, why?, so I can reach further with it and with more punch if I want to. For example, a 139gr SST with a BC of 0.486 I'm at 1,800 at 574 yds, but I if I want a little more punch I can use the 162gr ELD with a BC of 0.670 I'm at 1,800 fps at 584 yds, close one to the other but one has more punch. I rather hit the Elk with a punch from a 162gr than one from a 139gr to ensure more penetration.

For wind resistance obviously higher BC's are better, this will depend where you are hunting as well.

I guess it comes down to personal preference, for hunting some use Hunting bullets only and some use Match bullets because of their higher BC's.

So after all this rambling for me the answer is Yes, BC does matter, but other factors also come in to play.

 

[L.Sherm]

Now run the numbers with the bullets at the same velocity...

my comparison was same cartridge, apples to applesyours is completely different cartridge apples to oranges.

 

[L.Sherm]

I look at it as why add another 5 inches to an already poor wind call, I'll take 5 free inches of help on windage every time!!

I get what your saying Rian, but ask yourself am I really good enough to shoot a 1,000 and hold 51" or 56" that's with a steady wind and most 1,000 hunting situations are like that. So if its 10 mph were I'm at is it gonna be 10 all the way there or 5 at the target. I'll bet money if the vast majority of use including me couldn't hit a 8" steel gong 25% of the time in the situation I described.
I'm being totally honest with myself.

 

[bigngreen]

I get what your saying Rian, but ask yourself am I really good enough to shoot a 1,000 and hold 51" or 56" that's with a steady wind and most 1,000 hunting situations are like that. So if its 10 mph were I'm at is it gonna be 10 all the way there or 5 at the target. I'll bet money if the vast majority of use including me couldn't hit a 8" steel gong 25% of the time in the situation I described.
I'm being totally honest with myself.

It's often for me not what I'm currently capable of but what I'm working towards, kinda the same argument with things like spin drift and Coriolis many use, ya for some time we all will loose it in the noise but if your going to work your precision down tighter every year you will never get below the size of the noise you haven't cleared out, I attack it from the perspective of clearing out as much noise and tighten up everything possible right out of the gate so I have the fewest things that can be a possibility for a missed call.
I can dial that 5 inches, to me that's important enough to give consideration.

 

[adam32]

my comparison was same cartridge, apples to applesyours is completely different cartridge apples to oranges.

But that isn't strictly a BC comparison. If you run them at the same velocity you'll prove how the higher BC bullet has the advantage throughout the flight path.

Nobody is asking about cartridge, only BC.

 

[L.Sherm]

Rian you and I both know guys at Deep Creek that can shoot 2" and 3" 1,000 groups in good conditions but when the wind picks up then all the sudden you can see they start shooting 7, 8, 9 and 10" groups that just goes to show how stuff it is in the wind.
I guess what's the difference if you dial 56" or 51" it's just a couple clicks difference, the biggest factor is you better know EXACTLY how many.