Do I understand this correctly?

[Hover Sniper]

I understand the physics and the math behind Ballistic Coefficient (yep, I'm a geek), but want to understand the relationship between high BC, range and accuracy.

So with a bullet, say a 6mm BR Norma, with a BC of .495 (Berger VLD 105 gr) compared to a BC of .530 (Hornady Match 105 gr) using the same amount and type of powder and the primer, can I expect a higher velocity with the Hornady due to the reduced drag and therefore greater accuracy due to the increased velocity?

 

[Steve Blair]

No. You are confusing internal and external ballistics. Loaded to equal pressure with the same powder, in the same cartridge; the higher B.C. bullet will always show better wind deflection and downrange performance.

 

[lrgoodger]

The way I understand it, they should theoretically both leave the barrel at the same velocity (and that has been my experience exactly when comparing the 105 A-max and the 105 Berger hybrid), but the bullet with the higher BC (the Berger @ .547) 'flies' better than the Hornady (BC .500), so it will maintain altitude better and hit higher on the target. That is what I observed, but it was not much difference at 500 yards (my max range distance). I assume the difference would be more at further distances and the Berger would hit the ground much further out than the Hornady, not becasue it was going faster but because it 'flew' better.

 

[Steve Blair]

The way I understand it, they should theoretically both leave the barrel at the same velocity (and that has been my experience exactly when comparing the 105 A-max and the 105 Berger hybrid), but the bullet with the higher BC (the Berger @ .547) 'flies' better than the Hornady (BC .500), so it will maintain altitude better and hit higher on the target. That is what I observed, but it was not much difference at 500 yards (my max range distance). I assume the difference would be more at further distances and the Berger would hit the ground much further out than the Hornady, not becasue it was going faster but because it 'flew' better.

[br]
That is not necessarily true. It may be true of these two bullets but not of any given pair that happen to be the same weight. A Berger 105 Hybrid, due to reduced bearing surface, produces less velocity with the same powder charge than 105 VLD. I don't shoot or have any of the Hornady bullets but I find the contention that they will shoot at the same velocity as the VLD dubious.

 

[boltgunluvr]

BC is NOT indicative of accuracy. Never assume one's rifle will be more accurate with a higher bc bullet. As a matter of fact, there are rifles that won't shoot boat tail bullets well at all, but that does not mean that same rifle won't shoot accurately at long range.

 

[lrgoodger]

Everybody's right on target so far (even Sleepygator), but here is fact to back up my statement. I'm not one of those guys who posts, "Well, duh, I THINK it's this way."

I save every target I shoot with this kind of detail. You can't imagine how valuable that is for reference after you've forgotten what did what. Those velocities look pretty close to me. Load data is on the targets. These were shot at 350, 400 and 500 yards. I like the Amax group at 500.

 

[sceeder]

Go on you tube to Sniper 101
You will learn a lot.

 

[lrgoodger]

You can see on all three targets that the hybrid was flying slightly higher while leaving the muzzle at virtually the same velocity.

 

[Hover Sniper]

Two separate coefficient bullets leaving the barrels at equal velocity, the one with the higher BC will hit the target at a faster velocity, because it has less drag in flight. It will also fly flatter, retain more energy, and drift less.

These things will give the higher BC bullet an accuracy advantage, but will still be dependent on the rifle/barrel and loaded ammo to which will actually be more accurate.

Happy Shooting
Donovan Moran

It does make sense the velocity at the barrel would be the same, given the same weight projectile being propelled by the same amount of powder and lit off by the same primer. My intent was to make the only variable of this experiment be the BC. So the so-called accuracy is actually the reduced effects of Exterior Ballistics with the higher BC projectile, thus "fly" faster and flatter.

Thanks guys, I just got a Savage 12 BR in 6mm BR Norma with a 29" 1 in 8 twist barrel, and want to take it out to 1000 yds. This information will really help me when I'm finding my rifles sweet spot.

 

[Hover Sniper]

Irgoodger, your targets are great examples to support your comment. Thank you for sharing.

 

[mysticplayer]

I understand the physics and the math behind Ballistic Coefficient (yep, I'm a geek), but want to understand the relationship between high BC, range and accuracy.

So with a bullet, say a 6mm BR Norma, with a BC of .495 (Berger VLD 105 gr) compared to a BC of .530 (Hornady Match 105 gr) using the same amount and type of powder and the primer, can I expect a higher velocity with the Hornady due to the reduced drag and therefore greater accuracy due to the increased velocity?

BC value does not have any indication of accuracy potential. There have been a few very high BC bullets that shot horribly and have been discontinued. The BC is simply an indication of the drag of this bullet relative to a standard.

Print BC may also not be accurate as some companies create a BC from the bullet profile. These can be wildly wrong. Others shoot that bullets and calculate base on flight parameters. Better but also not perfect as each barrel can affect the bullet different and cause the inflight BC to vary.

Close enough for "govt work"

BC doesn't indicate muzzle velocity. Bullet diameter, bearing surface, jacket alloy are just a few things that can affect the friction of any bullet down any bore. more drag, less speed.

The only thing the BC suggests is that if you could get 2 bullets of different BC to leave the muzzle at the same velocity, the higher BC would loose less speed over the distance.

Finally, a BC value doesn't indicate it will land HIGHER. That really depends on how the barrel launches said bullet. Some bullets will cause the barrel to vibrate different and leave with a "low" barrel

Not good, not bad. Just what the barrel timing ends up for any kaboom.

YMMV.

Jerry

 

[Erik Cortina]

The short of it is, the bullet with higher BC will have a shorter flight time to target if launched at the same speed as a lower BC bullet.

 

[Raythemanroe]

Higher velocity at distance should be true.

 

[DRNewcomb]

My intent was to make the only variable of this experiment be the BC. So the so-called accuracy is actually the reduced effects of Exterior Ballistics with the higher BC projectile, thus "fly" faster and flatter.

I don't think you can actually eliminate all other variables, only minimize them. For instance, bullet weight is not the only thing that alters MV. There are other, such as the shape of the boat tail, free run, seating depth and composition of the jacket metal. You can really only work to reduce the other variables to a minimum.

What increased BC does is to reduce the drag and thus, the erosion of velocity over distance. For the same weight bullet this reduces time in the air (flight-time) and the impact of both cross-winds and gravity. Having less time for the wind to push the bullet off path and less time for 9.8 m/s^2 to have its impact.

 

[Steve Blair]

What increased BC does is to reduce the drag and thus, the erosion of velocity over distance. For the same weight bullet this reduces time in the air (flight-time) and the impact of both cross-winds and gravity. Having less time for the wind to push the bullet off path and less time for 9.8 m/s^2 to have its impact.

[br]
The bullet weight doesn't matter. A higher B.C. bullet, regardless of weight, fired at the same velocity, will have lower flight time and higher retained velocity.