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.

 

[wind gypsy]

The drift and drop equations are all about time of flight.

I've heard Chris Way and maybe even Frank Galli say this but yet every ballistic calculator seems to disagree on the drift portion of it. Otherwise lightweight, lousy BC bullets driven fast would have less wind drift in short to medium ranges than heavy much higher BC bullets but that is not the case far as I know.

 

[Bluefish]

I've heard Chris Way and maybe even Frank Galli say this but yet every ballistic calculator seems to disagree on the drift portion of it. Otherwise lightweight, lousy BC bullets driven fast would have less wind drift in short to medium ranges than heavy much higher BC bullets but that is not the case far as I know.

I believe it’s because wind is really drag related. Thus a lower bc has more drag and the wind has more effect even if time of flight is quicker. Drop is all about time of flight as gravity is the force at work.

 

[wind gypsy]

I believe it’s because wind is really drag related. Thus a lower bc has more drag and the wind has more effect even if time of flight is quicker. Drop is all about time of flight as gravity is the force at work.

That is my understanding as well yet people frequently talk about wind drift being primarily a function of TOF.

 

[wildernessrimfab]

Hammer has a new HBC bullet they just introduced.

Has anyone shot these yet?

I just ordered some of these in 264 120 gr. Curious about seating these pills in a 6.5CM when the drive bands are 0.200″ apart and the case neck is only 0.290". Hammer recommends 2 drive bands in the neck but that would put the end of the case near the "ridge" of the 2nd drive band, not the optimal location for a light crimp as Hammer also recommends. I'll find out I suppose.

 

[WhoGarrDen]

That is my understanding as well yet people frequently talk about wind drift being primarily a function of TOF.

In one of Hornady's Podcasts, Jayden Quinlan noted that the wind drift is tied to "lag time" (the difference between the time it took the bullet to get to target, and the time it would have taken in a vacuum). This is probably what determines the "rate" of drift (i.e. inches per second). TOF would still matter as it's coupled with the rate of drift. Jayden did note that even though one bullet could have a lower rate of drift, if it's taking longer to get to the target it will still likely drift more overall.

 

[wind gypsy]

I feel like even at 3-400 yards - shoot a 55 vmax or SBK vs a 75 ELDm at hundreds of fps slower. The light bullets will get to the target faster and will get pushed around more by wind.

 

[Bluefish]

I feel like even at 3-400 yards - shoot a 55 vmax or SBK vs a 75 ELDm at hundreds of fps slower. The light bullets will get to the target faster and will get pushed around more by wind.

The calculators suggest this is true. I was looking at my 25 prc with 134’s at 2850 vs a 25-06 with 80g at 3450. The 80g has similar drop but more wind than the 134.

 

[z987k]

I've heard Chris Way and maybe even Frank Galli say this but yet every ballistic calculator seems to disagree on the drift portion of it. Otherwise lightweight, lousy BC bullets driven fast would have less wind drift in short to medium ranges than heavy much higher BC bullets but that is not the case far as I know.

I misspoke. Wind drift isn't about actual time of flight. It's about lag time. Which is time of flight minus time of flight in a vacuum. This is why BC trumps MV for wind drift. It's 100% about the extra time it takes to get to the target because of the drag of the bullet, times wind.
The actual time of flight to the target could be identical between two different projectiles, but the one that had a larger difference in what it would have taken to get there should there have been no air is the one that will drift more.

 

[Obie458]

The Hammer HBC is new and offers some good coefficients for copper bullets. Another benefit of the HBC is lower pressure and higher velocity compared to traditional bullets. I was able to do some testing with the 141gr .284 bullet. The rifle was chambered in 280AI and had a 22" barrel. With very little effort I was able to achieve a .29" 3 shot group @ 3280fps. I'm told higher velocity is possible but if that load proves repeatable I'd be very happy.

 

[PLhunter]

The Hammer HBC is new and offers some good coefficients for copper bullets. Another benefit of the HBC is lower pressure and higher velocity compared to traditional bullets. I was able to do some testing with the 141gr .284 bullet. The rifle was chambered in 280AI and had a 22" barrel. With very little effort I was able to achieve a .29" 3 shot group @ 3280fps. I'm told higher velocity is possible but if that load proves repeatable I'd be very happy.

Did you crimp or just run it?

 

[AkMtnRunner]

I've heard Chris Way and maybe even Frank Galli say this but yet every ballistic calculator seems to disagree on the drift portion of it. Otherwise lightweight, lousy BC bullets driven fast would have less wind drift in short to medium ranges than heavy much higher BC bullets but that is not the case far as I know.

I did a comparison years ago of a 270 win and 6.5 creedmoor, which illustrated this. Similar weight bullets, the 270 sent worse BC bullets faster than the sleeker 6.5 did slower, but the wind drifts were similar out to 400 yards. Getting there sooner provides less time for the wind to work on the bullet, making up for some BC.

 

[wildernessrimfab]

Did you crimp or just run it?

I am developing a load for the Hammer .264 120 gr HBC. A light crimp helped with group size and velocity stats, but I havent yet experimented with different amounts of crimp. I have only tried no crimp vs 1/8 turn crimp on a Lee FCD...but the crimp definitely helped. Crimp also added about ~20 fps.