View Full Version : What's a point of Ballistic Coefficient worth?
07-25-2012, 12:56 PM
What's a point (say .01) of Ballistic Coefficient worth? Say, for example, if one round has a BC of .430 and another has a BC of .390, what's that mean in terms of performance? How much of an advantage is .040 of BC?
07-25-2012, 01:44 PM
Taken from the mouth of Wikipedia:
"A bullet with a high BC will travel farther than one with a low BC since it will retain more of its initial velocity as it flies downrange from the muzzle, will resist the wind better, and will “shoot flatter” (see external ballistics).
When hunting with a rifle, a higher BC is desirable for several reasons. A higher BC results in a flatter trajectory for a given distance, which in turn reduces the effect of errors in estimating the distance to the target. This is particularly important when attempting a clean hit on the vital organs of a game animal. If the target animal is closer than estimated, then the bullet will hit higher than expected. Conversely, if the animal is further than estimated the bullet will hit lower than expected. Such a difference from the point of aim can often make the difference between a clean kill and a wounded animal."
07-25-2012, 01:55 PM
There is no set value to a "point" of a bullets BC. There are a lot of other factors involved in this. By performance I'm going to assume you're talking about wind drift.
Just run the two bullets you're considering through a ballistics program and you'll have your answer. Have to keep in mind that a smaller (usually lower BC) bullet will have more velocity than the bigger. You'll want to input your best guess for MV to be most accurate.
Here is one for an example...
140 Berger Hybrids (BC .618)
10mph 90 degree wind
300 - 4.8"
600 - 21.0"
1000 - 66.3"
130gr Hunting VLDs (BC .552) 75fps faster than 140s (just a guess)
300 - 5.3"
600 - 23.2"
1000 - 74.6"
How far are you planning on shooting? If 500 or so yards and under, I'd pick the faster bullet and roll with that personally.
07-25-2012, 04:14 PM
Thank you both. And yes, I was thinking of wind drift when I posted the original question, but I said performance in case there were other things I wasn't aware of. I'm just trying to make a final decision on a couple rifles I've narrowed things down to (Weatherby Vangaurd 2 in 25-06 or Savage 11 in .260 rem). I know it's probably 6 of one, half dozen of the other, but I'm just trying to factor in anything I can think of, like BC, meat damage, availability and cost of ammo, weight, feel, etc. Trying to not overlook anything but, in reality, I'm probably just overthinking things (but that's fun too). Doubt I'd be shooting over 500 yards, so that's a good point too. Thanks again.
07-25-2012, 07:06 PM
If it were my decision I'd go with the Savage 260 for a few reasons. The 6.5mm's are very popular right now. There is amazing reloading options, as well as many people are starting to make some dang good ammo for them. They have great ballistics, as does the 25-06. Off the shelf ammo you'll probably have better luck with the 25-06. If you reload that dont matter. If you don't reload and want to buy some good ammo for that 260 take a look at Southwest Ammo, Corbon, and Copper Creek to name a few. They all produce much higher quality ammo than you can buy off the shelf. You will pay more though.
Also, you can't deny that Savages just flat out shoot well. I personally have never owned one, but know many who do and know many more who swear by them. I've seen them shoot. I have great confidence in them, and will probably own one or two someday.
Also, Savage would be easier to source aftermarket parts for if you eventually wanted to upgrade the stock and trigger.
07-26-2012, 09:06 AM
All very good points. I own one Savage (low end, 22mag) and I like it. I know people who own Weatherby's love them too. I don't reload, so that's one thing that pushes me toward the 25-06 (it sweems to be more available, and it also is a little cheaper). Thanks for all the good info.
07-26-2012, 10:47 AM
Both of those are excellent cartridges. The 25-06 doesn't have as many high BC bullets available as the 6.5 cal would. Both will greatly benefit from at least 24" of barrel to get most of their velocity potential. I shoot a 264 win mag and it delivers quick kills with 140gr accubonds. That bullet won't damage much meat on a lung shot and has the penetration capability to handle tough angles. The 130gr accubond would likely be my first choice to try in a 260.
Both rifles you are testing have an excellent reputation for accuracy. The Savage will have a more easily adjustable trigger, and I prefer the tang safety to the Vanguard's push safety. If you are looking to shoot long distances though, I'd lean toward a 260 with more than 22" of barrel. In my experience nothing beats a 270 win for performance from a 22" barrel. I've had a Tikka 25-06 with a 22" barrel that gave disappointing velocities, as well as a 22"280 Rem that wasn't nearly as fast as I'd hoped. Both of these have performed very well for me from a 24" barrel. For some reason the 270 seems to perform pretty well even with a 20" barrel. I've never owned a 260, but the 6.5x284 and 264WM benefit greatly from a longer barrel with their larger cases, and I'd expect the 260 to be the same way. With it's smaller case capacity it won't gain as much velocity from the long barrel but it will still be significant.
07-27-2012, 07:51 AM
At what I'm looking to spend, the Savage would be a model 11, which comes with a 22 inch barrel in .260 rem or 25-06. I've read that, of the two, the .260 doesn't lose as much with the shorter barrel. The Vanguard comes with a 24 inch barrel, but not in .260 rem (or any other 6.5), so that's why my choice there is 25-06.
07-27-2012, 12:07 PM
Hornady's website has a simple ballistic calculator you could compare trajectory and wind drift between different rifle/bullet options.
Here is a quick comparison with the bullet I'd personally choose to shoot from 3 of them with a 22" barrel. Your choice of bullet design, weight, and speed may be different and will change the results. I can change the ranges, speeds, and BC of any of these choices to make it look like it stomps the others, ammo companies do it all the time, but here is an example of how I examine ballistics programs to make decisions for myself.
Rather than compare everything with a 200yd zero I did it the way I sight in. I sight my rifle for the longest zero possible without going over 2.8" high during the trajectory curve. Any higher than that and I start shooting over coyotes and smaller critters at around 180yds as the bullet reaches the top of it's arc. I zero the rifle at the longest distance I can while staying at or below the 2.8" high point of the curve.
260 Rem, 130gr accubond (BC .488), estimated speed 2800fps
max height of 2.8" at 125yds, drops past 2.8" low at 260yds, 19.6" low at 400yds
25-06, 110gr accubond (BC.418) estimated speed 3050fps from a 22" barrel
max height of 2.8" at 140yds, drops past 2.8" low at 280yds, 15.9" low at 400yds
270 win, 140gr accubond (BC.496) estimated speed 2950
max height of 2.8" at 140yds, drops past 2.8" low at 280yds, 16.2" low at 400yds
Now to compare wind drift. I usually feel that anything over 5" of wind drift needs to be compensated for on my hold on a broadside deer-size animal. Using our data from earlier, in a 10mph 90 degree wind the bullets would reach 5" of drift at the following distances
Wind drift at 400yds is
As you start shooting further, the advantage of the higher BC bullet at a higher speed will continue to increase, and become much much more dramatic. The speed advantage of the lighter, lower BC bullet is pretty much spent by the 400yd mark and the higher BC bullets take over. If I had chosen to compare Berger bullets the 260 would have looked much better due to the high BC of their 130gr VLD. You should play with the numbers on a ballistics program like this yourself with the bullet weight & type you intent to use. Most velocities posted on a box of factory ammo or ammo maker's website are obtained with a 24" barrel, so I'd knock off 100fps from what they have posted for estimating 22" velocity.
As you can see, the differences aren't all that huge at normal ranges. In the field much more depends upon the shooter's ability than the rifles capability, but I still like getting all the advantage I can from my rifle. I tend to favor a 130-140gr bullet with a BC of around .500 with a velocity of around 3000fps for most of my hunting. This has given me good performance on game at a level of recoil I can easily manage. Managable recoil leads me to good shooting form and more practice.
For price and availablility of factory ammo the 270 will beat the other two pretty handily. Almost any bullet you see on a bullet maker's site can be found in a 270 factory load. I'm a big accubond fan and would try several factory loads to see which one loaded with an accubond shot best. I'd also have to try the 130gr Hornady Interbond, and 140gr SST Superformance loads to see if I could get good accuracy with their extra velocity.
The Savage is an excellent choice for a cheaper rifle, I don't think you will be disappointed. I love the tang safety as it never rubs into the fire position on my pack. The Ruger American is also pretty impressive as a budget rifle, lightweight and extremely accurate and also with the tang safety. It might be worth reading a few reviews on it if you are interested in a 270. After five 3 shot groups on different days while testing the reload I chose it is averaging .660" groups at 100yds. After the 4th shot it tends to start stringing shots vertically as the light barrel warms up. Pretty darn good from a $360 sub 6.5lb rifle, and all the reviews are claiming similar results. The trigger is easily adjustable and crisp, and the recoil pad is very good. The biggest downside I've seen is the forend is pretty flimsy and can contact the barrel if alot of pressure is put on it from a sling or bipod. I plan to open the barrel channel a little further.
07-27-2012, 04:34 PM
Thank you for taking the time to share all that knowledge. I'll check out the Hornady website. I know I'm splitting a lot of hairs, but agree with you about getting whatever advantage you can. I had the Ruger American on my list originally and have read quite a few reviews. Didn't really cross it off, just ended up focussing on the other two more and more.
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