barnesuser28
Well-Known Member
Barnes uses Doppler radar and time of flight tests to test B.Cs in their 300 yard underground test range.
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Experiment for quantifying lot to lot variations of powders
- Thread starter Michael Courtney
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rscott5028
Well-Known Member
Why should Berger publish BC's for multiple bands?
These are available in many cases from Litz. But, he's been a huge advocate of G7 BC's.
Has Sierra started publishing G7 BC's like Berger?
-- richard
Michael Courtney
Silver Member
Not to my knowledge. But we're now publishing both G1 and G7 BC test results for bullets we've tested.
See:
http://www.dtic.mil/dtic/tr/fulltext/u2/a555975.pdf
Hornady is using Dopper radar also on testing their new bullets. Dave Tooley is doing a lot of that testing for them and others.
Now it's too late to edit my earlier post putting Hornady's name in it as measuring time of flights for their bullets, it that's what they're doing. But it's good to know than more companies are getting real data to use.
One reason's that everyone won't be shooting bullets at the fastest speeds possible. And more accurate drop and drift numbers for folks using bullets in one band may be important to them. Some bullets have a pretty wide range of BC's; others have small ones.
rscott5028
Well-Known Member
But, G7 is more accurate than stepped G1 for long range, high BC, boat tails
...unless your software ony supports the G1 drag model
No doubt Sierra will catch back up eventually.
To Michael's point... independent studies and sufficient market pressure can influence manufacturers to turn out better products.
-- richard
Michael Courtney
Silver Member
http://www.appliedballisticsllc.com/index_files/S155grPALMAbullet.pdf
Here's a link to a nice Litz paper that describes the G1 and G7 ballistic coefficients for that very bullet.
Interesting information, but I'm not surprized at the results. Watched a test comparing Sierra's 30 caliber 190-gr. HPMK's to Berger's 30 caliber 185-gr. VLD's in velocity tests at 5 and 997 yards. With both bullets at the same speeds around 2550 fps from the same barrel at 5 yards, the Sierra's went through the 997 yard screens about 40 fps faster than the Bergers. Why 997 yards? The down range screens were centered a couple yards in front of the 1000-yard targets atop the safety berm. A velocity test between the different 30 caliber 155's would be very easy to do the same way as this one was. That would best show which bullet had the highest BC over 997 yards, but the exact numbers wouldn't be known. Calculations from timing flight in different velocity bands ends up with a BC that's close, but actual speed differences down range gives the best comparisons.
In the above tests, down range screens were two sheets of aluminum foil covered 1/4" thick foam boards about 3 or 4 feet square. Spacing was 6 feet as I remember. The front and back foil sheets of each one were connected to the start and stop inputs on the down range chronograph. As bullets passed through each one, they connected the two foil layers triggering the chrono's timing circuits. There was some talk about one bullet being slowed down more than the other as it passed through the foam boards due to its nose shape and weight and that might induce an error in screen to screen timing. No conclusions were made as far as I know. But an interesting way to chronograph speeds a long ways away.
'Twould be interesting to see accuracy tests with both 155's at 1000 yards with 3 different lots of each bullets shot in 100-round test groups from 3 different barrels mounted in action-clamped rail guns. Meanwhile, we have to accept whatever one gets with each one in shoulder fired tests with few-shot groups. Note also that Sierra's new Palma 155 has a higher BC than their original one.
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