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LoadBase 3.0 Mobile w/G7 BC Test Results

 
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  #15  
Old 04-14-2010, 03:01 PM
jrs jrs is offline
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

The thing that's been keeping me from going commercial with this has been the $800/each cost (to me) of the Pan/Zoom/Tilt Mega-Pixel camera that is the MINIMUM necessary for seeing itty-bitty holes in great big black targets under a wide range of lighting conditions.

Strangely enough the network link part is what I call dirt cheap by comparison; about $100 including my time to test and confgure two 1000mw transmitters to setup a Local Area Network (LAN) that spans the distance between firing point and target. The target end can be connected to a cheap network switch that then can connect the LAN to all sorts of stuff. One of those things would be a notebook (or desktop if you have a small generator or AC power available) that has a USB 2.0 port, which connects to a webcam (about $30 should get one that can resolve and LCD display on a chronograph).

My plan was to build complete systems including all of the hardware and configure/test it prior to delivery so it becomes a plug and play system. Was trying to keep cost under $1000 then under $1,500 ... I'm almost there, but the camera/resolution problem is the killer.

Using a 12V 7AH battery the radio links will run for DAYS without recharge - solar panels could make the LAN work round the clock for years. Problem is the additional equipment will need more power than that - but a 1KW generator could power a whole lot of equipment for a very long day of shooting.

The idea of having a cronograph at the target end got me to thinking that having the high res camera positioned at the exact point where your scope will be would allow you to be downrange adjusting while watching what it looks like from the firing point ... have to either have two cameras/computers or make one trip back and forth to switch the camera to the target end. Might be worth it in time saving? The camera has a 22:1 zoom ratio so the telephoto view would be (subjectively) about like a 6x or 8x scope in terms of magnification.

We can talk specifics if you want to email me.

jsnell@twincedars.us
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  #16  
Old 04-14-2010, 03:29 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

The purpose of integrating a downrange chronograph is to be able to measure BC (obviously). There's an easier way to do this, with acoustic sensors.

Using a chrono and mic at the muzzle in conjunction with a mic downrange gives you enough information (MV and tof) to calculate BC. The advantage of this set-up is that you don't have to shoot thru a small window on the chrono because the range of the acoustic sensor (microphone) is tens of feet and is omni-directional. If you could add the sound that the downrange camera hears to the sound recorded by a mic placed with the muzzle chronograph, you can gather:
MV (useful in-and-of itself for testing purposes)
tof (used in conjunction with MV to get BC)
video (to see the group forming)

This is just about everything there is to be interested in for an external ballistics test.

The system I use to measure BC's uses a chrono at the muzzle and several mics along the range. This allows the calculation of a velocity dependent BC, and lets you identify which standard is a better match for a particular bullet (usually G7). The set-up is very much simplified if you only have one downrange mic to deal with. Sounds like you already have all the hardware required with the exception of a mic at the muzzle chronograph, it's just a matter of integration.

BTW (phorwath) glad to hear you got such good results with the G7 BC and the 7mm 168 VLD in your test with LoadBase. Question: did you have to monkey with the retard coefficient at all, or did you leave it at the default value?

-Bryan
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  #17  
Old 04-14-2010, 03:34 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

sorry i cant help myself, but i gotta say this.... Phorwarth, just think of all the time, effort and money (not to mention blood, sweat and tears) you could have saved by just reading the G7 BC values off the berger website...

Last edited by groper; 04-14-2010 at 03:45 PM.
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  #18  
Old 04-14-2010, 04:36 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Quote:
Originally Posted by bsl135 View Post
The set-up is very much simplified if you only have one downrange mic to deal with. Sounds like you already have all the hardware required with the exception of a mic at the muzzle chronograph, it's just a matter of integration.

BTW (phorwath) glad to hear you got such good results with the G7 BC and the 7mm 168 VLD in your test with LoadBase. Question: did you have to monkey with the retard coefficient at all, or did you leave it at the default value?

-Bryan
Very interesting to learn some of what I don't know. How much cost in hardware to integrate a mic(s) with the equipment I already have? All I have now is two chrono's run in tandem with skyscreens mounted on a single rail system. Plus the AR 500 protective plate to protect my distant skyscreens.

My bad for not providing the LoadBase 3.0 drag coefficient (what you refer to as retard coefficient is termed as Drag Coefficient with LoadBase 3.0 ballistic software). No tweaking or modification of the drag coefficient. The predicted down range velocity of 1571 fps was based on the default drag coefficient value of 0.5
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  #19  
Old 04-14-2010, 05:00 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Quote:
Originally Posted by groper View Post
sorry i cant help myself, but i gotta say this.... Phorwath, just think of all the time, effort and money (not to mention blood, sweat and tears) you could have saved by just reading the G7 BC values off the berger website...
Ha! Always a spoiler in any crowd!

To be honest, I have to prove my loads and equipment at long range anyhow. Incorporating the down range chrono data collection after I've selected a test load for proofing at long range is just one added task that provides confidence and peace of mind. Now that I own the equipment, I enjoy adding this additional level of data collection and validation into my LRH preparation process. Once I chronograph the down range velocity, if I don't get a good match (I did in this instance) to ballistic software predicted velocity, then I tweak the drag or retard coefficient in my ballistic software until my predicted down range velocity matches my chronographed down range velocity. In this manner I know I'm inputting BC related information that's dead nutz 'on the mark' for that specific bullet and load in my specific rifle. Then when I'm hunting in other atmospheric conditions at widely differing ranges, elevations (station pressure), and temperatures, I have every reason to believe that the LoadBase 3.0 predicted dope will also be dead nutz on the money.

Most everyone develops drop charts, which are only good under the set of atmospheric conditions at which the drop chart shooting was performed. My method enables the creation of accurate real time drop charts for any set of atmospheric conditions, altitudes, latitudes, angle of shot, and direction of aim. Chances are good you already knew most all of this. But that's where I'm coming from in case you or others are wondering why all the fuss. If all else fails, sometimes I just tell folks "I'm an engineer" and they seem to understand - or else give up.

However... if it wasn't interesting, enjoyable, useful to my needs, and rewarding I wouldn't force it on myself.
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  #20  
Old 04-14-2010, 05:21 PM
jrs jrs is offline
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

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
jsnell@twincedars.us
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  #21  
Old 04-14-2010, 05:42 PM
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Re: LoadBase 3.0 Mobile w/G7 BC Test Results

Quote:
Originally Posted by bsl135 View Post
BTW (phorwath) glad to hear you got such good results with the G7 BC and the 7mm 168 VLD in your test with LoadBase. Question: did you have to monkey with the retard coefficient at all, or did you leave it at the default value?
-Bryan
Eglet 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.
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