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LoadBase 3.0 Mobile w/G7 BC Test Results

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Unread 04-14-2010, 06:04 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Originally Posted by Eaglet View Post
Eaglet answering. Phorwath please check if I'm right on the DC.

Yes, those predictions are based on the default value of the DC, which is 0.500.

The DC is a very good indicator of how well the BC was determined, among other aspects of the Drag Curve itself. (Your work is awesome!)

BTW, Bergerís program overpredicts by 30 feet/sec.
10-4 Eaglet. My LoadBase 3.0 predicted 981 yard velocity of 1571fps was indeed based on the LoadBase 3.0 default DC of 0.500

Which is why I stated Dang! when I reported on the correlation between my chrono'd velocity versus predicted velocity.
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Unread 04-14-2010, 07:38 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Sorry, phorwath, my bad. I did not realize you had already answered

that for Bryan.

Jesus Christ the same yesterday, and to day, and for ever.

Our Lord Jesus said that as it was in the days of Noah and
also as it was in the days of Lot so it shall be in the days...
It's happening again!!! God sent to us His prophet, and His Word
to this generation and we once more are rejecting it as was prophesied!!!

---> As promised, God Sent His Prophet to us!
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Unread 04-15-2010, 07:58 AM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Brian, how do you account for network delays? Do you get resolution greater than millisecond?

It's good to think of these things. I tested my system for delays with the following approach:
1) On my desk I placed the transmitter and receiver, as well as the 'muzzle' mic and ran both signals into an audio mixer.
2) I then generated a tone from my PC speakers of a known frequency.
3) By viewing the wave-form of the added signal (from both mics) I was able to determine the delay that's caused by the transmitter/receiver pair.

The delay was way less than 1 millisecond.

The only thing the above test doesn't account for is the time delay it takes for the signal to travel the distance from transmitter to receiver in the field. A few calculations with the speed of light will convince you this is negligible too. I know nothing about TCP/IP LAN protocols, so you would probably have to perform a similar test to see what the delays are using your equipment. My transmitters and receivers are simply modified walkie-talkies.

Another delay you'll have to account for (not in the electronics, but in the math) is the time it takes for the sound to travel from the bullet to the mic as it passes. This is a simple calculation with the speed of sound, but you have to make it part of the process. A bullet that passes 5 feet from a mic will add 4.5 ms to the instrumental tof which you have to subtract out. Same is true on the muzzle end, but if you afix the mic to the chrono, the distance is only a few inches.

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Unread 04-19-2010, 01:43 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Originally Posted by jrs View Post
Brian and all,

The microphone downrange is an excellent idea, but getting the real time of arrival of the bullet downrange via a TCP/IP based LAN is somewhat problematical as the protocol is likely to add a variable delay. (Now I've got to go figure out if the delay variability is significant!)

I'm thinking I would need to sync up a pair of clocks using NTP and then read microseconds between events from the clocks on each end, but I may be over-engineering for the scale of events. Would require dedicated equipment that I can design and build but don't have 'off the shelf' at this point ... unless the clock in the downrange router will do it ... hummm

Brian, how do you account for network delays? Do you get resolution greater than millisecond?

Shouldn't we start a new thread for this discussion? Call it something like range instrumentation ?

John Snell
Don't worry about hi-jacking this thread. Part of the theme to this thread is recording extreme distance down-range velocity, and it sounds like that's a feat that's right up your alley. If you're able to provide the techno wizardry that would allow me to obtain 1000 yd time-of-flights so that I can determine BCs and 1000 yd velocities, at a cost comparable to purchasing an additional chronograph (or a tad more), then I would be very interested. I don't really need to see the impacts on target remotely with the video gear.

I'm an engineer but I'm not schooled in electronics and would rather pay someone else for the research, design, development & construction/instruction. Then simply purchase something that will make the collection of 1000 yd time-of-flight & BC/velocity less of the ultra-marksmanship task of having to place my bullets through a ~4" X 9" chronograph skyscreen window at 1000 yds. PM me or post here if you think you're on to something. Bryan makes it sound relatively straightforward, but that's the way technical stuff is - after you've spent the time and research to thoroughly understand it. Prior to doing the research and development, it seems pretty mystical!

PS: If you do start another thread, please let me know so I can follow your work effort!

Last edited by phorwath; 04-19-2010 at 05:42 PM.
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Unread 04-19-2010, 04:26 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Well, since you feel that way I'll keep on natering about with this for a bit.

Got into a discussion on the subject with a co-worker who has vast experience in time functions of networks and operating systems (was involved in nuclear reactors and petro-cracking tower ops). In his opinion only a certain extinct propretary real-time operating system is deterministic enough to do the job.

I think that there must be a cost effective way to get there from here using a digital network.

I was just reading some of the Sierra discussion about their instrumentation and see that they are much more accurate than that, and end up at about +/- 2% on the BC. Fron what I gather they have a very long wire between crono screens, and a custom cronograph ... but what the don't have is 1,000 yards.

I suppose a plain old analog radio could substitue for the long wire, but I'm more interested in finding a way to use a digital network.

I'm going to keep working on it and I'll put a post here when I get an idea I think might work.

If anyone has an idea or time to look on-line for a device that can get time of flight accurately and post back here I'll see what I can do to integrate it with what I already have.

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Unread 05-02-2010, 08:50 PM
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Re: Another LoadBase 3.0 w/G7 BC Test _ Range = 985 Yds

Here's the lowdown on my latest field test with the Hornady 162gr A-MAX. Comparison of Patagonia Ballistics' LoadBase 3.0 predicted 985 yard velocity (using Bryan Litz's G7 BC = 0.307) versus measured 985 yard velocity.

Cartridge is .280 RCBS Improved with 28" 1:9" twist Brux barrel. I captured two (2) 985 yd velocities over my chronographs; 1) 1580.9 fps, and 2) 1582 fps. This yields a two-shot chronographed 985 yd average velocity = 1581.4 fps.

Environmental Conditions = 29.43 in/Hg, 47F, 48%RH
60.4 degrees North Latitude
50 degree direction-of-fire Azimuth
Muzzle Velocity = 2948 fps
Stability Factor = 1.64 with the 162 A-Max in my 1:9 twist Brux.
Default Drag Coefficient = 0.500

LoadBase 3.0 (with coriolis and spin drift features activated) predicted 985 yd velocity = 1590.2 fps versus the chronographed 985 yd velocity = 1581.4 fps. A difference of 8.8 fps @ 985 yds, for another very good correlation between predicted velocity (using the G7 BC and the default LoadBase 3.0 Drag Coefficient of 0.500) versus measured velocity.

I'll tweak the G7 BC in my LoadBase 3.0 saved "Track" from 0.307 to 0.305 in order to obtain a better predicted match to my measured 985 yd velocity. Gus would probably tell me to tweak the Drag Coefficient, but this is such a small modification to Bryan's G7 BC that I think it matters little which is tweaked.

The 1/2" AR500 protective plate prevented bullet destruction to 4 skyscreens today. The AR500 steel is tough stuff. I can't see or feel any surface deformation where the bullet impacted. Nothing more than a surface splash on the white paint.

Photo of my chronograph setup showing the 4 skyscreens that survived the "near-death" experience. I don't install the orange and white skyscreen shades at distances past 300 yds.

Last edited by phorwath; 05-03-2010 at 10:54 AM. Reason: Correct transcription error in measured velocity
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Unread 05-03-2010, 06:15 AM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Phorworth, your work is phenominal. Please continue to post your results and the comparisons. I am fascinated by the fact that the Loadbase is producing predictions that are as close as your work indicates. GREAT WORK. rc
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