Range Report Labradar derived ballistic coefficient

[JCCinOhio]

I'm working up a coyote round for a 243 using the Speer #1205 75gr varmint bullet. Published BC is .234. I saw on JBM that they had a BC calculator so used the near/far one to see how close the labradar derived BC was to the published. For 5 shots I looked at a few data points from each with separations from 20 yds to 60yds, and they all came up with a BC of between .179 and .183.

Where I hunt I can shoot out to 800 yds easy, but can't use it as a range to see what really happens.. Furthest I can shoot easily is 185 yds, and I don't think that's enough to see what my bullets would do to 500? According to JBM, the difference between .180 and .234 is about 12" at 500 yds, so a missed coyote.

So question is, what should I use for a BC for shooting out to 500yds?

 

[spife7980]

The only way to really know is to really do it and find out.

 

[JCCinOhio]

So if I can get a few shots off at 500yds.. I assume I measure how low the impact is from my point of aim/zero and then play with the BC in JBM till it matches? Say I can get 5 shots off.. better to do all at 500, or mix it up and go as far out as I can?

 

[Lowlight]

Too short a range,

it will be the best bullet you ever tested, there is a reason you don't read about more people fine tuning their BC with a Labradar, it won't work the range is too short

you need at least 300 yards, farther is better

 

[sab567]

I have to agree,
Labradar is great stuff, but you can't go further than about 100-130 yards wich is not an absolute number to confirm a BC. You can check if AB have trued the BC of your bullets, wich normally is a really good start. But after that you'll have to go and try it yourself.
Personnaly AB BC have always been dead on.

 

[Lowlight]

Most of the AB BC numbers are from 300 too

Hornady is currently doing 800 yards, which is the farthest, but you have to go into their expanded breakdown of the numbers

AB Numbers are okay, but they are no different than most others. He still uses 300 yards.

 

[CoryT]

To get a BC with chronograph numbers over a 100 yard range requires a tunnel. Distance between centers of the screens needs to be precise to under an inch. The Labradar is simply incapable of the required precision to generate an accurate BC. For long range work, even the best 100 yard number would need adjustment. You need either downrange velocities or drop, preferably both and precisely measured. BC varies enough between loads, guns, muzzle devices etc. that for long range work there is no substitute for range work.

 

[FromMyColdDeadHand]

Could you put the Labradar behind a berm (or naked), pointed down range and shoot rounds into cone of the radar and use the doppler trigger?

 

[Lowlight]

No,

Hang it up, everyone has tried a host of options, they don't work

 

[JCCinOhio]

So the process... Leave my rifle at my zero distance (130yds) shoot out to distance x.. which will prob be 450-500yds if I can get the farmer to let me shoot there.. then shoot and measure MV and drop at range, get atmospheric data.. and plug into JBM, adjust BC till drop matches?

I don't see shooting past 500 with this bullet at a coyote at the places I can hunt..

 

[Rocketvapor]

I took my 100yd results, using chrono speed and Hornady mid range B.C. for the 88 ELD-M and came up with 12 MOA @600 yds.
Went to a 600 F-Class match and my Clean Cold Bore Shot is my avatar.
As I continued I refined my drop to 11.5 MOA.
Subsequent meets have ranged from 11 to 11.5 based on video review of my strings.
I now start sighters @ 11.5 and adjust from there based on drop in current conditions.
When the weather permits I'll get back out and check velocity with a second hand MS Sporter instead of the Competition Pro I have been using.
But, since both the 100yd and 600yd range I use are both less than 10 feet ASL, I'll probably just use a little temperature correction to decide on starting @ 11.25 or 11.5

 

[Longshot231]

I've used the Labradar and JBM to determine the B/C for bullets that are not in their library.

Early on I made a mistake. I learned about my mistake from attending one of the ABS seminars put on by Bryan Litz.

When you are recording your weather conditions while chronographing the bullets, use the STATION PRESSURE for your location. DO NOT use the barometric pressure.

The STATION PRESSURE is the atmospheric pressure for your location and your elevation.

The barometric pressure is what pilots use. It is the atmospheric pressure at sea level for a given location. That pressure is set in the altimeter so that all aircraft flying in that area are using the same reference so their altitudes are correct.

The bullet doesn't care about the atmospheric pressure is at sea level. It only cares about the atmospheric pressure for the altitude that it is traveling at.

Here's how using the barometric pressure can mess you up instead of using station pressure.

I have a barometer app on my iPhone. Where I am sitting out now, the terrain elevation is 811 feet. The station pressure is 28.89" HG. The barometric pressure (at sea level) is 29.75" HG.

Notice that the pressure at sea level is greater than the pressure at my current terrain elevation of 811 feet. That's natural as any 4th grade science student knows.

AND I should have realized that as well! Nevertheless, I put the barometric pressure in the JBM calculator for the ballistic coefficient.

I plugged in the average muzzle velocity and average downrange velocity in the JBM ballistic calculator using the barometric pressure rather than station pressure. If you are keeping up with me so far, you can already see how this is going to affect my firing solutions and how it differs with the actual trajectory down range.

To put it in simple terms, the barometric pressure told the JBM calculator that the air was thicker than it really was. With the given velocity down range in the [perceived} thicker air, the solution told me that the B/C was greater than reality.

In other words the calculator thought that I was shooting a more efficient bullet.

So what happened when I started shooting? I ranged the targets at 800 to 1000 yards that day. Everything was impacting low.

I double checked everything. I used a SIG 2400 ABS range finder as well as the data from JBM. The firing solutions were really close but I was still striking low on the targets.

After my "eureka" moment at the seminar I finally realized why I was shooting low.

I went back out and fired the rounds again but used the STATION PRESSURE for my location. Don't forget that using the station pressure told the JBM calculator that the air was thinner than it is at sea level.

So that same bullet wasn't as efficient as it appeared to be if it was traveling in thicker air (according to the calculator). In other words, I gave the JBM calculator incorrect information which made it think the bullet had a higher B/C.

Using the correct pressure it gave me a lower B/C. Now when I use the SIG range finder with the correct B/C, the firing solution gives me a higher holdover as does JBM.

Now the bullets don't hit low.

Hope that makes sense.

 

[Lowlight]

you really want to play with the BC around 800 yards,

you set velocity at 600 and BC at 800

If you do it shorter odds are the numbers will be close, BC is a distance thing, it takes time for the numbers to start to stack up. Inside 500, like 300 - 400 you are not gaining anything worth worrying about.

It's for beyond 600

 

[LawnMM]

Be cool if somebody came up with a radar unit like a labradar with some kind of remote triggering system that fired it up when the rifle discharges.

I remember the Steinart or whatever that was supposed to be deployable downrange but it didn't get much traction.

Given all guys making home rolled video equipment with power sources and directional antennas for the video signal I'm surprised we haven't seen this yet.

 

[spife7980]

So the process... Leave my rifle at my zero distance (130yds) shoot out to distance x.. which will prob be 450-500yds if I can get the farmer to let me shoot there.. then shoot and measure MV and drop at range, get atmospheric data.. and plug into JBM, adjust BC till drop matches?

I don't see shooting past 500 with this bullet at a coyote at the places I can hunt..

Here is a link to a post I made awhile back where I show the differences between velocity and bc on the dope at range. A quick summary is that inside of 600 yards bc doesnt really matter, velocity is king.

https://www.snipershide.com/shootin...een-ab-and-ballisticarc.6961805/#post-7976008

 

[Lowlight]

I have the Steinart,

It will almost work at distance, it's a sound meter as long as the shot is supersonic it will work

The problem is, the microphones are so close together getting a perfect shot over the unit is an issue. The vertical spread can corrupt the numbers.

 

[stevenc23]

Shotmarker gives a MV (as well as SD/ES) at the target which can be placed out as far as you like. Have been comparing velocities at the Barrel and the target and they line up well when looking at what my ballistic calculator estimates the MV to be at the target. SDs between Magneto and Short Marker are similar as well.

 

[rangerlong]

Using my weatherflow, labradar and jbm my calculated BCs come out very close to ABs. Always within .010, usually about .002 off using good quality target bullets.

I did learn that using the measurement from just 1 shot could yield inaccurate results so now I use the average of 5+ shots, and results are much more consistent and closer to ABs.

 

[AIAW]

I’ve found BC’s to be good for comparative shopping, that’s about it. You mix in all of the environmentals, MV, etc. and you have a number that‘s simply not true. The marketing wank fudge factor has historically been witnessed across some manufacturers also.

So many different softwares have varying methods of calculating drop these days, vertical deflection options and pure algorithm differences. Pick one, enable or disable it and keep it that way!

I always calculate everything. Don‘t think I have used a published BC in ages, at least not in the end.

 

[Rocketvapor]

As some bullet manufacturers start standardizing how they calculate B.C. the values are closer to real world results. When one inflates a B.C. in advertising they often gets called out and suffer just a little.
Published data is a starting point.
To do better you need enough shots to determine just where the geometric mean of your group hits.
When you can't actually see the center of a group, it ain't a group, it don't got no precise drop.

 

[JCCinOhio]

For SNGs can anyone tellme the BC in AB for the Speer #1205 75gr varmint bullet (.243)?

 

[Longshot231]

For SNGs can anyone tellme the BC in AB for the Speer #1205 75gr varmint bullet (.243)?

i tried looking earlier and couldn’t find it.

 

[Quickshot]

Oehler‘s System 89 BC Chrono will calculate BC. But, I don’t use it. The published BCs are close enough to start trueing the BC to my rifle.
The Lab Radar is consistent enough to expose variable BC issues. I captured the multi-range plots and the rogue shots were always out of the group low.

Here’s what a 10-shot string looks like using a different load.

Cheers,

 

[Ledzep]

BC is fairly mach and stability dependent. As Frank said, 0-200yd isn't the place to test it. Lots of noise up close and the higher BC #'s you'll get for your higher velocities up close won't be a good average for your long-range trajectory.

 

[CoryT]

I've had good success with a well built and aligned Shotmarker target combined with a LabRadar. The LabRadar gives very good muzzle velocities and the Shotmarker provides a downrange velocity at 1000 and 1500. In an ideal world, you shoot through two Shotmarker targets at once, I can do 500-700 and 1000-1200 at once depending on basic trajectory. That provides 3 points of velocity and two points of elevation. It's not super simple to setup, but it's about the best you can do absent the System 89 or Doppler.

 

[Lowlight]

Just wait for the Oehler 89 Bufford is working on with them

if you want downrange stuff in a single package the new Oehler will be the ticket especially when combined with the software they are using.

But the Shot Marker done right is a better option than the labradar as noted above

 

[CoryT]

Agreed, the 89 sounds like the hot ticket, though it will be a bit more expensive than the Shotmarkers and a LabRadar. Until I get hands on with the 89, I'm not sure it will actually provide better data, though the setup and number crunching should be simpler. The LabRadar alone is clearly inadequate. There is some added flexibility with the Shotmarker/LabRadar combo. I have the luxury of being able to setup that combo as required, and I could permanently setup the 89, so for me neither is an issue. I'm still on the list for an 89 when they can deliver

 

[Lowlight]

I think the software package is supposed to be robust for it,

They gave me something on it last year but it was Windows based so I haven't looked at it,
But the 89 is supposed to have a pretty robust desktop software package to run the system which is supposed to do the work for us.

I should see if I can get into it and post some stuff on it in a new thread.

But my understanding talking to them at SHOT is the key to this is the software, more so than the hardware alone.

but agreed on all points

 

[JCCinOhio]

So 495yds was the max I could shoot.. got in 5 shots each before the rain, I know, not enough shots, and not far enough, but it's what I could do.. With the resulting average drop (.243) this yielded a BC of .193 vs the Labradar .180, and the manufacturer's .234. For my 308 with 110gr vmax, book BC is .290, I got .299.. and for the .223 with 55gr vmax I got .232 vs book .255... Will try using the turrets to dial these drops in next time and see how it does.