338 bullet BC results from Snipers Hide

[Autorotate]

The currently assessed performance (BC's) for the Berger 300 grain Hybrid is derived from 1000 yard testing, not 600 yards. The originally assessed BC's for the Gen 1 version of this bullet were done at 600 and were inaccurate (something like .890/.450 G1/G7). Since then, I only test .338's at 1000 yards, and the current BC's have been measured repeatedly in several tests at 1000.

Bryan-Were the 7mm and 30 cal bullet BCs published in Vol 1/Vol2 of Applied Ballistics derived from 600 yd or 1000 yard testing?

 

[BryanLitz]

Autorotate,

I can tell you that prior to testing the .338's in ~June of last year I would test at 600 or 1000 depending on location, etc. After observing the error in the case of the .338's, I decided to start testing the higher BC bullets only at 1000. This includes the heavy 7mm's and heavy .30 cals. I also went back and re-tested any high BC bullets that only had 600 yard data for them and re-verified the numbers at 1000 yards. There were a couple cases where the numbers needed revised, but only a couple % one way or the other.

Take care,
-Bryan

 

[elkregulator]

tag for later

 

[jmason]

I donated some 325 gr rocky mountains and some 300 grain cutting edge to the next round of testing. Bryan if you'd like to test some as well I'd gladly send you some.

 

[BryanLitz]

I would like to test these. PM sent with my address.

Thank you,
-Bryan

 

[Bearwalk]

There is another program (mobile app) currently under development that I'm more directly involved in. This 'Applied Ballistics' app will have the ability to use 'custom drag curves' for a number of long range bullets. These custom curves are in no way related to any 'G' standard, so BC's are out the window all together. Rather, these custom drag curves will represent the exact drag of each bullet at each and every speed.

Bryan,

I applaud this move to get away from BC's. As you probably know from my posts over at SH, I heap a lot of scorn and blame on the good ole BC.! I'm sure you are not quite where I am, yet , but the move to a custom drag function is long overdue and is really the main reason I quit relying on commercial programs and wrote my own.

 

[BryanLitz]

Bryan,

I applaud this move to get away from BC's. As you probably know from my posts over at SH, I heap a lot of scorn and blame on the good ole BC.! I'm sure you are not quite where I am, yet , but the move to a custom drag function is long overdue and is really the main reason I quit relying on commercial programs and wrote my own.

Probably the biggest challenge to this approach is sourcing the custom drag curves. How do you get them? A better question; how to you supply accurate data for 100's of bullets? As everyone knows, just because an idea is better in theory doesn't mean it will be better in practice if the supporting data isn't good. I have what I feel is a pretty solid plan for creating custom drag curves for many bullets that I've tested. I'm also open to evolving this plan if/when better methods become available.

BC's are an old idea and we're not limited to them anymore for computational reasons, but they still do a lot for us and face it, for the 99% of shooters who don't shoot at ELR (ranges where bullets slow to transonic speed) there is little improvement to be had over a good G7 BC.

-Bryan

 

[bigngreen]

Really interested to see how well the Cutting Edge bullets actually do, the claims seem a little high in light of how similar copper bullets did in the SH test.

 

[Bearwalk]

Probably the biggest challenge to this approach is sourcing the custom drag curves. How do you get them? A better question; how to you supply accurate data for 100's of bullets? As everyone knows, just because an idea is better in theory doesn't mean it will be better in practice if the supporting data isn't good. I have what I feel is a pretty solid plan for creating custom drag curves for many bullets that I've tested. I'm also open to evolving this plan if/when better methods become available.

BC's are an old idea and we're not limited to them anymore for computational reasons, but they still do a lot for us and face it, for the 99% of shooters who don't shoot at ELR (ranges where bullets slow to transonic speed) there is little improvement to be had over a good G7 BC.

-Bryan

All good points.

I certainly concede that if your are not shooting long range, then there is indeed little to be gained by moving away from the BC, unless of course, it is no longer the industry standard. This leads to what I am advocating, which is for the manufacturers to follow Lapua's lead and start moving to a "drag curve" standard. If a manufacturer is collecting data to provide a stepped BC, then they are almost there anyway. If they are providing a BC from shop drawings and McDrag type calculations, then they would obviously feel some pain in changing their ways.

I'm certainly not saying that providing data for an entire line is going to be cheap or easy, but if the marketplace starts to demand it, the early movers are going to see a competitive advantage. I would also posit that your "laboratory" efforts have given most manufacturer's a pretty good basis to get going.

I also believe that if a "drag function standard" movement did begin to gain traction, there would also be a need for a standards committee to develop a white paper on how these data should be collected and the results reported.

My humble apologies to the OP, if I have strayed too far off topic.


Jeff

 

[Pdvdh]

The currently assessed performance (BC's) for the Berger 300 grain Hybrid is derived from 1000 yard testing, not 600 yards. The originally assessed BC's for the Gen 1 version of this bullet were done at 600 and were inaccurate (something like .890/.450 G1/G7). Since then, I only test .338's at 1000 yards, and the current BC's have been measured repeatedly in several tests at 1000.
Here is my full reply to the Snipers Hide thread regarding the test results:

"As some of you may remember, when this bullet (the .338 cal 300 grain hybrid) was first released (Gen 1), I had assessed inaccurate performance (.455/.889, G7/G1) based on testing at 600 yards. Further testing at 1000 yards indicated the currently assessed performance of .418/.819, G7/G7.
The cause for the discrepancy in my results is not attributed to BC decay at 1000 yards vs 600 yards, but rather testing at 600 yards is simply too error prone to work with larger caliber, high BC bullets. In other words, normal uncertainties in MV, range, atmospheric variables etc result in unacceptable % uncertainties in measured BC. When measuring the BC of a high BC bullet, the test has to be conducted at longer range in order to manage the measurement uncertainty."

This was why I stepped all the way out to 1000 yds when collecting downrange velocity to determine TOF BCs for bullets fired out of my rifles. I wanted to maximize the change in velocity between the muzzle and the downrange measuring point to minimize the uncertainty in measured velocities associated with chronograph collected velocities. I knew there was some amount of error inherent in the chronograph velocity data, and I wanted that error to be a small percentage of the total difference in velocity from the muzzle to 1000 yds downrange.

It makes it challenging to place the bullets over the skyscreens at 1000 yds though. Which is why I built a 1/2" AR500 skyscreen shield to protect my skyscreens from stray bullet impacts. I now shoot across 7 skyscreens (triplicate chronograph setup) so I'd lose all seven skyscreens with a single stray bullet.

 

[Gerard Schultz]

the difference between advertised and measured (BC) for the solids is 19% in the case of the GS bullet,

I have been trying to address this matter but find that any post I make about it at SH is deleted. I have given the correct numbers (and why) here.

 

[jmason]

Well the rocky mountain and CE bullets I provided didn't fair so well. The apparently need a tighter twist, more velocity or both.

 

[bigngreen]

Well the rocky mountain and CE bullets I provided didn't fair so well. The apparently need a tighter twist, more velocity or both.

I saw that, what bullet weight did you send in.

 

[Broz]

Well the rocky mountain and CE bullets I provided didn't fair so well. The apparently need a tighter twist, more velocity or both.

I read that too, what twist were they shot from? I thought they were tac drivers from the normal twists. I think I heard someone refering to there groups as " One minute of Water Buffalo"

Jeff