Home Forums Hunting & Shooting Hunter's Campfire Ballistic Coefficient Question

Hope this isn’t a foolish question…

Looking through different rounds within particular caliber, BCs can vary depending on quality of manufacturing, the type of tip etc, but in general the BC tends to go up with the weight of the bullet. Some calibers are known for having better BCs throughout their weight range even when compared to a larger caliber. That makes them preferred for some shooters for longer ranges because of course they retain more velocity and have less drift down range. Does anyone know the physics behind why that may be true? I understand why larger rounds WITHIN a particular caliber have a higher BC. They have more length and weight for a given diameter. But why do certain calibers stand out compared to others as having higher BCs throughout their weight range? Hope that made sense.

INot me. I ignore it. Don’t really understand the physics.

Mostly.
I do favor heavier tho, if accuracy is there. I am a giterdone guy. If the game flops, I’m happy!

I have been curious about this too, and have wondered if there is something mathematically "poor" about the .257" and .277" diameters, or if those calibers have never been asked to have high B/Cs. That is to say, for whatever reason manufactures don't put much effort into designing high B/C bullets in those calibers.

I hope some knowledgeable folks chime in, without the usual guesses disguised as being informative.

I wonder if it has to do with the caliber’s capacity for powder. In other words, if a particular caliber can support more powder for a given diameter, a round with a longer and heavier bullet could be designed for a given speed.

Probably cause they would never be able to sell any more new chit.





Take care, Willie

Naw that can’t be it because bullets, not cartridges, are listed with BCs.

Ballistic coefficient is a measure of how easily a bullet passes through air. Long slender bullets (6.5x66) tend to have high BCs. Short fat bullets (Elmer Kieth 44) tend to have low BCs. Sharper tips raise BC. Boat tails reduce drag at the rear of the bullet. All published BCs should be taken with a grain of salt.

High BC bullets fly flatter. They also, somewhat surprisingly, experience less wind deflection.

I'll take a stab at this.

First think of BC as "how slick is my bullet" expressed mathematically.

Now think about the calibers that tend to be so high in BC....6.5's, 243, 7mm....etc. The 6.5 has largely (minus Remington flopping the 260) had tight or fast twist rates. They tended to shoot long bullets. Longer bullets require more twist to stabilize.

So now there's a bunch of 8 twist guns shooting blunt bullets that are an inch long and doing it well.....getting a long pointy bullet to be able to chamber is easy because the rifles are used to long bullets is gravy.

The typical 6 and 6.5 cartridges leave enough room in the magazine to be able to take advantage of these long bullets.....not so much in a 300RUM.

There's big money thrown at super slick bullets, but honestly at most hunting ranges a decent flat base bullet will often shoot better and do very well to 500+ yards.

In the same vein, why is the 6.5 and 7mm an "inherently accurate" ?

Some calibers when introduced were with lighter bullets intended for normal hunting ranges with the highest velocity possible at the time. They became established in 25 and 277 caliber. The standard twist was suitable for the bullets of the time. With twist rate established to slow to stabilise higher BC bullets.

35 caliber is another that doesn't have high BC bullets.

Longer bullets have better BC but need a faster twist barrel to stabilize. If I recall, some older caliber barrels are typically mfr’d w slightly slower twists, making the long, heavy high BC bullets less accurate…am I close?

Weight, in and of itself, does not affect Ballistic Coefficient. If you have two bullets of identical profile, one made of copper, and the other's a standard cup and core, they will have the same ballistic coefficient, and at the same muzzle velocity, will have the same flight characteristics. Sectional density's a measure of weight relative to bullet diameter, so the cup and core bullet will have the higher sectional density.

Could you explain your logic here? I am not getting it.
All else being equal, wouldn't a heavier bullet have a higher B/C? It has more mass and thus more momentum and/or inertia, right?

Physics ain't my thing.

Thought experiment:

BC is a measure of how easily a bullet moves through air.

IHow does the air "know" what is inside the jacket? It doesn't. So to calculate BC all you need is the bullet geometry. A hollow aluminum jacket and a solid tungsten bullet with the same geometry will have the same BC.

BC is just one factor that influences trajectory. Muzzle velocity, mass, and BC all enter into that calculation.

So, a baseball and a same sized nerf ball have the same B/C? It sure seems like a baseball thrown at the same velocity has a much higher B/C, as it keeps its speed much longer and generally goes further. Drag coefficient I can see based solely on bullet profile, but not the actual ballistic coefficient. Apparently velocity also plays a factor and B/C can change with velocity, which gets me doubly confused.

I am totally lost here...

I get lost too


All I concern myself with: does my bullet’s construction match my velocity range. Is it going to deliver energy, shock, expansion, sufficient weight retention and lethality to flesh and bone? Or is it going to barrel through?

Payloads and distances really start to matter further out beyond 200 yards.

Rifle, cartridge and bullet manufacturers have traditionally followed sales of conventional calibers in generic bullet weights with low bc's and slow barrel twists that were optimal for them .... all due to the usual Joe Bob deer hunter taking the largest share of sales, the Joe Bobs didn't need high BC bullets and wouldn't know what to do with them anyway, stagnation in bullet BC was the result with most manufacturers unwilling to pursue R&D into making better BC projectiles and barrels properly twisted in factory rifles

Walt Berger was huge in changing that with the advent of his 6mm bullets and Berger continues to be the leader in high BC copper jacket/lead core bullets and since 2019 have delved into solid copper high bc target bullets as well

With long range shooting (both hunting and target) leaping into the stratosphere in the last decade... especially in the last 4 Trump years, we have seen smaller solid copper bullet makers like Cutting Edge Bullets, Badlands Precision, Hammer Bullets, and Lehigh take bullet design way into the next level up to where conventional lead core bullets of same caliber cannot attain the same BC's

Now back to your question .....
BC's in a particular bullet diameter/caliber ? all calibers are capable of maxing out on bc, as diameter increases, bullet design, length and weight will contribute to higher bc's until you hit max possible with current tech and bullet metallurgy, all that will be required is faster barrel twists to properly stabilze a given bullet bc and design, but as weight goes up you will also need larger capacity cartridges to shove these bullets out faster to make full use of the higher BC's

The long range target/competition world has evolved and we now have projectiles, cartridges and rifles capable of being competitive out to two miles and beyond, a lot has happened in the last decade, and these improvements have made their way into hunting bullet designs as well

Badlands Precision have really raised the bar high with their new "Super Bulldozer 2" hunting bullets, you won't find a higher bc hunting bullet anywhere else on the planet

Per my request a few years back, tailored for a cartridge design I was working on ......they have developed and brought to market the sleekest, highest BC 30 caliber hunting bullet ever designed....... I was fortunate to have shot the first 100 pcs ever made and tested the bullet on an Alaskan bull moose last September with phenomenal results

The only hurdle is rifling twist, you'll have to acquire a correctly twisted barrel to make use of the bullets... as ALL the rifle manufacturer haven't quite caught up yet to these fantastic bullets ....,,,


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This.

Some calibers be it tradition or what have you settled on lighter for caliber bullets than others. Those light for caliber chamberings generally do not have a barrel twist fast enough to stabilize a longer bullet and so manufacturers limit what they offer in longer bullets. On the other side of the coin long range shooters that can have a gun chambered in anything they want choose calibers that have a large choice of bullets already available. There are other factors such as recoil and suitable chamberings but having a large spectrum of suitable bullets plays a role.

Long streamlined bullets have only been an advantage in hunting since the popularity of rangefinders and scopes with turrets. Those two things and the recent popularity of long range precision shooting are the reasons for the trend in heavy for caliber bullets. Assuming that the trend keeps going that way I think we’ll eventually see more choices for those bullets in .25 and .277 caliber. The 6.8 Western was created with the purpose of making a .277 caliber rifle that’s based on a short action with enough mag box and fast enough barrel twist to shoot heavy for caliber bullets. The 277 WSM has a slower barrel twist and the mag box isn’t long enough to avoid seating longer bullets deep in the powder charge. If it winds up being popular you’ll see more heavy for caliber bullets offered for .277 (6.8).

Most of us don’t live in places or do the type of hunting where the ultra heavy for caliber bullets are needed. I’d personally just as soon hunt with a lighter TTSX moving fast. Guys that regularly shoot out past 500 yards are mostly driving the trend and it trickles down to Joe Bob hunter.

As an aside note those already available heavy for caliber and match grade bullets is what the 6.5 CM was built around. Guys that say it isn’t any faster or can’t do anything deer hunting that a Swede or 260 Rem can’t are right. The reason that it’s been so popular is that it works as well as the other two in a hunting rifle but the chambering is well suited to long range precision shooting and banging steel at long range popular with younger shooters today that didn’t grow up hunting. 6.5 CM has less shoulder taper so it can fit in a short action rifle and still seat bullets out far enough to not encroach to much on the powder charge and comes factory in fast twist barrels. That and the 30 degree shoulder angles proven to be inherently accurate and a pretty good combination of decent velocity with popular hunting and long range match type bullets moderate recoil have made it popular. When you compare similar bullet designs with similar BC’s at similar velocity in 6.5mm and .30 cal you’re going to get some fairly significant added recoil in .30 cal and would be running a lot more gun likely chambered in a magnum length action and heavier than needed bullet for typical deer hunting.

Aside from all the known hurdles and barriers that prevent manufacturers from delving into projectile improvements ...

The WIFE is probably the biggest obstacle of all time... lol !


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😂