Lab Radar and BC measurement

[Uriah, SASS # 53822]

While were talking about chronographs in a separate post, I was wondering if any of you dived into the BC?

 

I’m looking for a Paul Jones 45001 BC. I’m using the estimation BC of .357

 

I know LabRadar is capable of this, And based on my brothers experience, is difficult to use (Been waiting for the BC 3-4 years now).

 

Garmin looks like it’s easy to use, but doesn’t offer the BC. Although, I’ve talk to some users, and they say that there’s an app for a Garmin, that offers a myriad of information, minus the BC.

 

Thanks,

Uriah

[Cholla]

BC being the bullet's ballistic coefficient? Hornady had a podcast about bullet BC, and my takeaway is that the BC changes with velocity.

[Cholla]

 

[Still hand Bill]

You can estimate the BC with Lab radar, you cannot with a garmin unless you have more than 1.  I would say it’s has decent accuracy, but probably not enough for dialing in long range dope.  Within +/- .02 would be my guess on accuracy.  I have checked a few bullets and Barnes and Hornady data seems to be spot on.  Others have been up to .15 off published.  Always worse, so they are slowing down faster than expected. 

to do the calculation, set up the LR to return speed at 25, 50, 75, 100 yards.  Then get your data.  Lab Radar is picky on aiming so don’t be surprised to miss a few data points.  Take the data from a shot and plug it into the Hornady ballistic calculator, adjust the BC until it matches your data.  Now you have an approximation of your BC.  
 

I stumbled upon this when I looked at data for a particular bullet and it was going 400-500 fps slower an 100 yards than at the muzzle. Wondered why.  Turns out the bc was worse than published.  

[Happy Jack, SASS #20451]

At the moment the only way to measure BC is with a really big doppler radar (about $100,000.00) or with an Oehler system 88 or system 89. They are both rather expensive.  I have a system 89, one of only a handful in the US.  To get accurate BC's on supersonic cartridges you must go out to transonic distances which can be difficult  on most ranges.  I have steel out to 1 mile so I can do most cartridges up to 338 Lapula. For subsonic cartridges trying to get accurate BC's is usually a waste of time especially for pistol cartridges.

[Smokin Gator SASS #29736]

How accurate or far off are published BC in load manuals. Most of them do publish them but I guess shooters find that they are not accurate? 

[Uriah, SASS # 53822]

10 hours ago, Cholla said:

BC being the bullet's ballistic coefficient? Hornady had a podcast about bullet BC, and my takeaway is that the BC changes with velocity.

Cholla, yes, you are right. On the other hand, black powder cartridge rifles, 45-70, top out at 1200 ft./s. And from the graph, it’s almost a straight line function. The games we play with the BPCR, the range are known. I’m interested in the wind deflection.

Thanks,

Uriah

[Cholla]

1 hour ago, Smokin Gator SASS #29736 said:

How accurate or far off are published BC in load manuals. Most of them do publish them but I guess shooters find that they are not accurate? 

Many are way off because the test equipment was not that accurate at the time. Many bullet makers still don't have the equipment to test the bullets as they travel accurately. From what the experts say, often the BC was an educated guess.