LoadBase 3.0 Mobile w/G7 BC Test Results

[Pdvdh]

Patagonia LoadBase 3.0 Mobile ballistic software users may find this post intriguing. I've been using LoadBase 2.0 Mobile, the upgraded LoadBase 3.0 Mobile, and now the recently updated LoadBase 3.0 with the added ability to input G7 ballistic coefficients. LoadBase 3.0 Mobile only accepted G1 BCs until this recent update.

With LoadBase 2.0 Mobile and the initial version of Loadbase 3.0 Mobile (G1 BCs), I had already been shooting Berger VLDs in my 300 Win Mag (210 VLD) and 7mm Rem Mag (168 VLD) . I had already recorded velocities with the 210 & 168 VLDs at the muzzle, 290 yds, and 987 yds over a dual chronograph setup, which helps to confirm I'm getting credible chrono readings. With these velocities, I used the Drag Coefficient (DC) tab in the Analyzer Module to develop a G1 BC and a DC for both bullets.

With these BC and DC values input into LB Mobile, I field tested the LoadBase predicted drops at 295, 600, and 987 yds with both bullets. The 210VLD POIs from my 300 Win Mag were dead nuts on with the LoadBase predicted drops. The 168VLD POIs were a pretty good match, however I did tweek the DC value with the 168VLDs in order to improve the predicted drops closer to my measured drops.

After Bryan Litz announced he was coming out with G7 BCs for the Berger bullets, and after I learned LoadBase 3.0 would be updated to allow use of G7 BCs, I was looking forward to using Bryan's G7 BCs with LoadBase 3.0. I was thinking this combination might result in very good correlation of predicted drops to field tested POIs.

Since I already had the field drops (POIs) and chrono'd velocities out to 987yds for both bullets, after Gus released his G7 BC LB3.0M update, all I needed was some time to input the Berger G7 BCs for both bullets into LB3.0M to learn how close the predicted drops and velocities matched my actual field drops and velocities.

Well I finally made time and here are some G7 BC LB3.0 Mobile results:

168 VLD. . . LB3.0 G7 BC (DC=0.5) Predicted . . . . Chronographed Velocity . . . . Difference
290yds . . . .2621 fps . . . . . . . . . . . . . . . . . . . .2632 fps . . . . . . . . . . . . . . 11 fps
987yds . . . .1643 fps . . . . . . . . . . . . . . . . . . . .1673 fps . . . . . . . . . . . . . . 30 fps
168 VLD. . . LB3.0 G7 BC (DC=0.5) Predicted . . . . Measured Drop . . . . . . . . . . Difference
987yds . . . .-195.1" . . . . . . . . . . . . . . . . . . . . .-190.9". . . . . . . . . . . . . . .. 4.2"

210 VLD. . . LB3.0 G7 BC (DC=0.5) Predicted . . . . Chronographed Velocity . . . . Difference
290yds . . . .2546 fps . . . . . . . . . . . . . . . . . . . .2546 fps . . . . . . . . . . . . . . 0 fps
987yds . . . .1553 fps . . . . . . . . . . . . . . . . . . . .1584 fps . . . . . . . . . . . . . . 31 fps
210 VLD. . . LB3.0 G7 BC (DC=0.5) Predicted . . . . Measured Drop . . . . . . . . . . Difference
987yds . . . .-211.4" . . . . . . . . . . . . . . . . . . . . .-207.1". . . . . . . . . . . . . . .. 4.3"

I used the default DC of 0.5 with the Berger G7 BCs. LB3.0 Mobile / Berger G7 BC predicted velocities at 987yds were ~30 fps slower than my chronographed velocities with both bullets. The predicted drops at 987yds were ~4 1/4" greater than my measured drops with both bullets. The predicted 987yd velocities are ~1.9% less than my chronographed velocities. The predicted 987yd drops are ~2.1% greater than my measured drops.

My opinion? I'm pretty pleased with these LB3.0M G7 predicted values.

 

[Eaglet]

Phorwath,

Thank you for sharing. It's very interesting!

 

[BryanLitz]

Phorwath,
Thanks for posting this. That is a pretty good match.
I'm curious about a couple things;
1) Your chronograph set up that lets you measure velocity that far downrange.
2) How does JBM compare to your measured data (using G7's)?

It's great that we have a mobile option for G7 BCs now.

Take care,
-Bryan

 

[Pdvdh]

Phorwath,
Thanks for posting this. That is a pretty good match.
I'm curious about a couple things;
1) Your chronograph set up that lets you measure velocity that far downrange.
2) How does JBM compare to your measured data (using G7's)?

It's great that we have a mobile option for G7 BCs now.

Take care,
-Bryan

Bryan,

Yes, considering all the potential background errors and noise a person can add to the data collection process, I thought those results were certainly within the margin of error. I'm sure I could tweek the drag coefficient in LB3.0 Mobile for a very close fit to my measured data, but I just wanted to test the software with the G7 BCs and the default drag coefficient value of 0.5

1) I run both an Oehler 33 and a PACT PC2 in series with the skyscreens mounted on a single rail using a 6 foot spacing and 4.5 foot spacing, respectively. This way if the difference between the two recorded velocities is out of whack, I have a way of knowing that either one, or both, of the chronographs spit out an erroneous value and I can discount or completely disregard the data. I don't worry about getting the same velocity from each chrono. I only worry about the magnitude of the difference between the two values on a shot to shot basis. For example, on a good data set when the equipment doesn't give me any hiccups, the actual difference between the two chrono readings (with one brand, style, caliber, and weight of bullet) over a string of shots might vary between 17 to 22 fps. Sometimes I've had 6 or 7 shots where the difference in velocity over all of the shots will only vary by a maximum of 3 fps for any single shot. Then I'm feeling pretty darn good about the quality of the collected data... If I get a data set for a shot such that the difference between the recorded velocities is 30-55 fps, or 0-10 fps (when the average difference should be 17-22 fps) then I know I've recorded a bogus value from one or both chronographs and I can disregard, or at least qualify, those values. Having two chronographs recording each and every shot is quite an eye opener in itself. It causes me to smile anytime I'm engaged in a conversation with another shooter who's scratching his head trying to interpret chrono data from a single chrono. In my experience, I would no longer even think of getting serious about the collection of, and reliance on, chrono data for purposes of load development without a dual chrono setup to provide this type of confirmation that the data are trustworthy.

As far as how do I chrono at 987 yds? It takes nerves of steel if you haven't fabricated some kind of protective device to protect your sky screens. And I didn't. It's not something I do on a regular basis - my nerves can't handle it! I'm trying to figure out what type of a skyscreen protector I might be able to construct. Something shy of parking a bulldozer blade in front of my skyscreens. In addition, it involves a lot of back-and-forth driving, because I have to drive down to the target / chrono's after each and every shot in order to confirm whether or not the shot was placed good enough to collect velocities. Alaska is 4-Wheel Drive country and I start out will a full tank of gas.

2) I haven't run this comparison with JBM and the G7 BCs. Hadn't even thought about it, but I may do that as a point of curiousity. I was eager to run the LoadBase predicted values because LB3.0 Mobile is what I have in my toolbox when I'm hunting. If I run JBM G7 data I'll post those results also.

 

[Eaglet]

Phorwath,

I was just re-reading your thread and... man I've got to tell you, you really got
nerves of steel to shoot through your chronos at 987 yards with no protection.
I just don't think my rifle, or my ammo nor me are good enough to do the same. I do have tow chronograps and plan on having them for a long time.
That's great work, awesome shooting.
Thanks again for taking the time to share that.

 

[jmason]

Buddy, you've been busy!! I also concur your crazy for shooting through your chronograph at 987 too!! However I do thank you for doing it! Great post!!

 

[Pdvdh]

Re: Pics of Skyscreen Protector

Next time I shoot at 1000 yds my skyscreens will be protected from bullet damage by this protective stand I constructed last month. 12" diameter, 1/2" thick AR 500 steel plate on an adjustable-height stand. The stand is welded to a piece of railroad tie for stability and support on the ground. Two pieces of square channel steel which tube within each other, comprise the adjustable stand. AR 500 steel plate is adjusted to height required to protect the skyscreens. The idea is to shoot just over the top the AR 500 plate which will run the bullet right over the dual sets of skyscreens. If a bullet comes in at skyscreen height it will be blocked by the AR 500 plate. This way I won't need the rubber underpants while squeezing off the trigger.

Here's a few pics:

First the protective AR 500 steel plating spraypainted white.

Next the adjustable stand showing cross pin and holes drilled every 1 3/4" to select proper height.

Lastly, the piece of railroad tie supportive base I decided to use. The sliding adjustable steel post separates from the AR 500 plate and the railroad tie for purposes of transport.

At 1000yds, I believe the 1/2" thick AR 500 plate will stop any bullet I plan to shoot out of any of my rifles. Max will be 300 SMK from a 338 Edge -> 1000 yds.

 

[Eaglet]

Re: Pics of Skyscreen Protector

Good built!

 

[Pdvdh]

For those with the interest:
I chronographed another Berger .284 168VLD Hunting bullet this past Saturday at long range. Distance was 981 yds. Bullet fired from my .280 RCBS Improved. I've chronographed this load pretty extensively in load development and it has a SD of less than 5 fps, based on about 8 different shooting sessions and a total of about 30 rounds chronographed. [By the way, the load is 62.2 grains H1000, Federal 210 Match primers, Lapua 30-06 brass, from a 28" Brux barrel.] Confidence in MV is high and I use the exact same chronograph setup at 981 yds so if the chronograph reads a little low or higher than the absolutely true velocity, there will be negligible affect on bullet BC determination from the chronographed data. BC is a velocity difference-based calculation, and if the true velocity is 10 fps faster than recorded at my muzzle, it will likely be 10 fps faster than recorded at 981 yds also.

Atmospheric Conditions: Station Pressure 29.85 inHg; 39 F; 42% Humidity

Chronographed Velocities:
Muzzle velocity = 2920 fps
981 yd velocity = 1569 fps

Using Patagonia Ballistics LoadBase 3.0 ballistics software, I entered the atmospheric conditions and Berger's advertised G7 BC of 0.316. LoadBase 3.0 predicted a 981 yard velocity of 1571 fps. Again, my chronographed velocity, captured with my dual-chronograph setup to help ensure credible data, was 1569 fps. A chronographed velocity (1569fps) which differed from the predicted velocity (1571fps) by only 2 fps at 981 yds! Dang! Pretty incredible correlation.

I only captured one reading at 981 yards because a very slight wind began to move my bullets left and right of the skyscreens by the time I had all the equipment set up and ready to go. The one shot I captured was dead centered over the skyscreens and cleared them by about 2 inches. Just barely cleared my AR 500 protective plating.

PS: I feel much better shooting over protected skyscreens.

Also, H1000 seems to be incredibly stable at temperatures from 4F to 68F with this cartridge. Most of my chronographed MV data was collected in ambient temperatures between 32 to 45F. Once I was happy with the load and the low ES/SDs, I chronographed a few shots in the backyard with both a room temperature rifle and ammo, and then again with the rifle and ammo placed in a 4F chest freezer for 8 hours prior to firing. The difference in MVs over these temperature extremes fell within the normal variation of all the chronographed shots fired between 32 to 45F. I was surprised the MV didn't drop off at 4F.

 

[Eaglet]

Really enjoyed reading that!!!!!

Very awesome. Have to admit you're a good shot!

Would I do it even with the protection? My lock I ruin both of them!!!!

Thanks for posting!

I hope you have received some of my e-mails I sent your way.

 

[Autorotate]

Great testing, and thanks for sharing.

 

[rhouser]

+1. Great testing and build job on the protection. rc

 

[jrs]

Hi all,
I have a prototype up and running of a camera system that will send very high resolution images up to 10 miles over a lightweight, inexpensive battery powered radio link. My original purpose was to provide a realtime view of small caliber bullet impacts on paper targets at ranges of 1000 yards and beyond, so I got interested when you mentioned having to drive downrange to read the cronograph. For THAT purpose I may have a much less expensive solution (still waiting on one component), but if you own a (cheap) SPARE computer to put downrange (out of harms way) I can show you how to use an inexpensive webcam to read the cronograph on another computer at the firing line. For that matter the radio link network can connect you to almost any sort of downrange instrumentation, and it may be inexpensive enough to put up at intermediate locations as well. And before you ask, no I haven't got an annemometer setup yet, but that's high on my to-do list. I'm very interested in any ideas and feedback about this project, and whether or not it has commercial viability.

 

[Pdvdh]

Interesting. I couldn't say how many chrono at those distances, but the convenience of that type of equipment is apparent to anyone that does. I have to drive back and forth multiple times with my current equipment, to adjust for proper POIs and check for data collection on the chronos. As with most things in life, cost will be a significant factor. I've got extra laptops, so if the additional equipment is cost effective, they could be a good match and I could envision some of us LR fanatics parting with their money and purchasing the additional hardware.