High BC copper bullets?

[DagOtto]

Thanks Bluefish and Madcalfe.
Have updated with your additions plus cutting edge extended range.
Those Cayuga's have some bad-ass BCs if they are accurate!

 

[DagOtto]

In playing around with developing the ideal rifle and hand loads for hunting with copper bullets, I took a different look at BC. I started with the ideal impact velocity of 2200fps which seems to be the recommended "actual" effective impact velocity for many copper bullets. I set that 2200 fps goal for 400 yards which will allow me to shoot to 400 with a high level of confidence that bullet performance and wounding will be ideal.

Then, I worked backwards to what my Muzzle Velocity needs to be with various bullets of difference BC's in order to hit that goal of 2200fps at 400 yards.

I was pretty surprised that the required muzzle velocity to achieve my goals varies by a giant 400 feet per second between the "worst" BC of .4 and the best of .65. So just by picking bullets with the higher BC's you can make a velocity improvement that is equivalent to switching from a .308 WIN to a .300 Win Mag.

Clearly, for copper bullets that require fast impact speeds, BC matters a lot, even when looking at 400 or 500 yard max. shooting distance.

I am also embarrassed to admit that I had never realized that bullets of completely different calibers with completely different weights will behave identically if their BC's are the same. For example: a 260 grain .338 bullet with a BC of .450 and a 120 grain .243 bullet with the same .450 BC, when fired at the same muzzle velocity, will have the same drop and wind drift at all distances.... weird.



shoo

 

[sz28]

I killed a bull last December using the 125gr Maximus. Bullet worked as expected shedding petals with the base continuing on. I was shooting uphill from 280yds. Bullet entered, passed through the lungs and stopped under the hide on the opposite side. Impact velocity should have been around 2250fps. As the petals shed they caused quite a bit of additional damage, including one petal that traveled through to the spine, causing the bull to drop instantly and tumble. Unfortunately I forgot to take autopsy pics. Overall the bullet worked as the manufacturer described and BC was fairly accurate out to 500yds in my rifle.

 

[z987k]

I am also embarrassed to admit that I had never realized that bullets of completely different calibers with completely different weights will behave identically if their BC's are the same. For example: a 260 grain .338 bullet with a BC of .450 and a 120 grain .243 bullet with the same .450 BC, when fired at the same muzzle velocity, will have the same drop and wind drift at all distances.... weird.



shoo

If you look at the formulas for drop and drift, weight is nowhere to be found.
You'll see comments all the time about how you need a heavier or larger diameter bullet to "buck the wind", but neither of those are variables in wind drift. All that comment does is tell everyone else they don't understand exterior ballistics.
I think this is an area where our calculators are holding people back in understanding. Just like in school where the teacher made you show your work and not use the calculator so you'd have an actual understanding of what is going on instead of becoming a biological servo for a computer.

 

[Bluefish]

If you look at the formulas for drop and drift, weight is nowhere to be found.
You'll see comments all the time about how you need a heavier or larger diameter bullet to "buck the wind", but neither of those are variables in wind drift. All that comment does is tell everyone else they don't understand exterior ballistics.
I think this is an area where our calculators are holding people back in understanding. Just like in school where the teacher made you show your work and not use the calculator so you'd have an actual understanding of what is going on instead of becoming a biological servo for a computer.

While not directly in the calculation, weight does show up indirectly in bc when looking at a single caliber. Ie a heavy for caliber has a higher bc so drift and drop are less. Also longer is usually higher bc and higher weight. While it’s not exactly correct that heavier is better, it’s not wrong either. It’s what I like to call redneck engineering. Observing a phenomenon and then explaining in a completely wrong way.

But comparison between calibers, weight is not really relevant.

 

[Unclecroc]

Apex afterburner
McGuire copper rose
Hammer hbc
Pva Cayuga

 

[z987k]

While not directly in the calculation, weight does show up indirectly in bc when looking at a single caliber. Ie a heavy for caliber has a higher bc so drift and drop are less. Also longer is usually higher bc and higher weight. While it’s not exactly correct that heavier is better, it’s not wrong either. It’s what I like to call redneck engineering. Observing a phenomenon and then explaining in a completely wrong way.

But comparison between calibers, weight is not really relevant.

Ya, just because sometimes it fits doesn't mean it's correct.
Weight is kind of in there because SD is in BC and weight is in SD, but it tells you nothing about the form factor. You can very easily have a 200gr 30 cal with a .25 G1 and a 110gr 243 with a .6. The latter will perform better in every metric.
Or a .6 180gr 30 cal and a .25 200gr 30 cal.

It is fundamentally incorrect to say a heavier or wider bullet has less drift or drop because it is heavier or wider. Often heavier bullets do have less drift and drop given the same MV, but it's not because they are heavier.
The drift and drop equations are all about time of flight.