We (KnS and I) discussed the difference between our results at length when their assessments were published. To summarize, we are very eager to pursuit joint testing in order to learn what we can from each other in order to provide consistent and repeatable test results. When this joint testing comes about, I'm sure we'll address this forum with our findings.
In the mean time, I can share more information regarding my test results with the .338's.
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.
Due to the initial discrepancy of my own results, I proceeded to conduct extensive testing on this bullet at 1000 yards to be 'sure' it was right. The following are my test results by date for this bullet:
date: barrel, performance (G1/G7)
6/1/2010: 1:10-9" gain 30" Bartlein, .819/.420
6/5/2010: 1:10-9" gain 30" Bartlein, .811/.415
6/5/2010: 1:10" 28" Krieger, .825/.422
6/5/2010: 1:10" 28" Krieger, .825/.422
7/7/2010: 1:10" 27" Sako (TRG-42) .822/.421
2/15/2011: 1:10" 27" Sako (TRG-42) .809/.414 *note; low confidence test due to poor light conditions and suspect chrono #'s
2/24/2011: 1:10" 27" Sako (TRG-42) .817/.418
During the 6/1/2010 test, the bullets were also shot for 'drop' at 1000 yards which resulted in BC's of .824/.413. These results are considered lower confidence than the rest of the (tof based) results due to the uncertainties related to drop testing for BC. Nevertheless, the numbers line up well with those derived from tof.
The compiled results make up my (Berger's) assessed performance of:
G1 BC = .818, and G7 BC = .419
I don't think the difference in our results (KnS and mine) are related to BC decay between 1000 and 1200 yards. It's true that G1 BC's vary widely with Mach number, but the G7's wouldn't be 7% different based on just 200 additional yards of flight. There's something else about the tests that are producing different results. It's curious that we measured the same BC for the SMK (the first bullet they tested) and the % error between our results steadily grew thruout the day in the same direction from 0%, to +2%, to +4%, to +7%. Their measured BC for the SMK was only 2% lower than the Berger Hybrid. Just looking at those two bullets side by side reveals dramatic differences in shape which ought to add up to more than 2% difference.
Based on the extensive and consistent test history I have for this Berger bullet and the feedback I've gotten from ELR shooters in the field, I'm confident in my current performance assessment for this bullet. However I'm still very eager to get together with KnS to see if their result is repeatable, and if so, why it's different from mine. It's not about ego or being 'right' for the sake of argument; rather it's about learning how to conduct consistent, reliable, repeatable, and meaningful ballistic performance assessments so that other shooters can make well informed decisions about their hard-earned money.
There are other interesting trends in the KnS test results besides the minor difference in measured BC compared to my results.
1) The difference between manufacturer advertised and measured BC for all the conventional (jacketed) bullets is less than 10%. However, the difference between advertised and measured for the solids is 19% in the case of the GS bullet, and 47% for the Predator (
Match). I couldn't find advertised BC's for the ZA276 or the 245 Lehigh. This dramatic discrepancy of claimed performance for monolithics is documented in chapter 18 of my second edition. This is not to say that monolithics are bad, but simply that it's difficult to estimate what the performance will be due to the radical nature of the designs. Factors such as driving bands and additional skin friction drag (from longer lengths) are a couple reasons why it's hard to nail down what the drag will be. But even with the actual performance known, they can be very good, accurate, reliable, consistent bullets capable of reaching out effectively to very distant targets. Just be careful to be realistic about the performance.
2) Although the Berger 300 grain Hybrid has the highest BC of all the bullets tested, that doesn't mean it's necessarily the best overall choice due to the lower MV it's capable of. I figured most of this crowd understand that, but wanted to point it out for clarity.
3) KnS test identified the 245 grain Lehigh as being the actual 'lowest drag' projectile in the test, having a G7 form factor of .92. This is a bullet I've not tested so I can't comment on that result from a verification POV, but I can say that my performance assessment of the 300 grain Berger is a G7 form factor of .90 (a little better than what they measured for the Lehigh).
As you can see, you can make several conclusions about trends that are universally supported by both my and KnS' work. Some conclusions are somewhat supported by both, and some conclusions are simply contradictory. So the tests were a success in the sense that they shine some more light, and when we get a chance to sort out our testing methods together, hopefully we'll get that light focused and revealing the same answers.
Happy Holidays,
-Bryan
