Does anyone measure bullet velocity at the target? Can this be done with a chronograph (assuming you don't actually hit the chronograph)? I would like to know how much velocity is in the bullet at the time of impact. I'd like to consider this data and at what distance the 6.5 Creedmoor is really falling below transonic speeds.
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Measuring the velocity of the bullet a target distance
- Thread starter yo-yo
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I believe the shot marker system can do this, but not sure on the accuracy of it.
Tried it at 200 m (218 y) with .22LR and .308W placing my Garmin at range.
Works well with both caliber as long as you shoot up to ~14 IN beside or above it
Manufacturers BC are pretty accurate nowadays, with a V0 you should be able to determine pretty accuracy your subsonic range.
Works well with both caliber as long as you shoot up to ~14 IN beside or above it
Manufacturers BC are pretty accurate nowadays, with a V0 you should be able to determine pretty accuracy your subsonic range.
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The Shotmarker is quite precise, assuming you make a good frame. I use it during XLR here at Gunsite. The radar chronos will work if you can put the bullet in the beam and use Doppler triggering, the original LabRadar works. The ShotMarker requires the bullet to be supersonic, the radar does not.
ya you need MV for sure. It's going to be close enough. What's your intended purpose of that data?
Labradar will capture velocity going down range at various user defined distances. Works well to about 125 yards.
Using the jbm calculator I was regularly about .002 off published BCs.
Really nice for those bullets where there are no published BCs.
Using the jbm calculator I was regularly about .002 off published BCs.
Really nice for those bullets where there are no published BCs.
If its accurate enough to build a model to hit your target, its going to be close enough to not worry about. Its a simple calculation based on bullet speed (which we know from the model) and bullet weight.
Manufacture BC's outside of Berger are usually dogshit and unreliable. Never use the info from the box. Use what AB tells you and what your chrono tells you.
You can go in the ballistic solvers and look up the G7 library for yourself.
Hornady is notorious for over advertising their BC's.
Berger's head ballistician is/was Brian Litz... The guy who owns AB.
I've only ever used 2 Hornady bullets 30 cal 250gr A-tips and 375 cal 390gr A-tips
The BC's seemed to be pretty close. The CDM's work much better
Yup. I always recommend using the CDM if they have one. Its a banded model and incorporates different BC's at different velocities.
I stopped truing dope for my match guns because they all line up.
Would the Oehler be the answer?
@Buford Boone
oehler-research.com
@Buford Boone
System 89 BC Chrono™ – Oehler-Research
Oehler Research Ballistic Coefficient Chronograph The System 89 measures the calibrated ballistic coefficient for each bullet fired. At very long ranges, the shot-to-shot uniformity of the […]
oehler-research.com
Yes, kind of.Would the Oehler be the answer?
@Buford Boone
System 89 BC Chrono™ – Oehler-Research
Oehler Research Ballistic Coefficient Chronograph The System 89 measures the calibrated ballistic coefficient for each bullet fired. At very long ranges, the shot-to-shot uniformity of the […]
The '89 measures time of flight (TOF) and will report BC in multiple drag functions. Some target configurations report velocity at the target but it is a calculated velocity based on a measured TOF and the drag function you chose. Changing drag functions can (usually will) result in a changed target velocity. Once you shoot, you can compare multiple drag functions for that test without re-shooting.
If the drag function is a good match for your bullet, the velocity reported should be very close to actual - certainly close enough to determine if it is within the window for terminal performance.
If you use it to match TOF on a Radar Measured Drag Function, you are comparing your bullet to the same model of bullet measured by the manufacturer, using radar. That should give the best prediciton if you are within the distance they actually measured. What I call "Medium Range Radar" will track a .30 cal bullet about (varies with terrain, etc.) 1800 meters. All performance beyond that is estimated.
The '89 will work in supersonic and subsonic. The farthest I've used it is 2 miles. Currently, the limit is 10 seconds TOF. That, obviously, is subsonic, requiring an impact target. We have screwed three sheets of plywood together to create an 8' x 12' target - much easier to hit at distance.
Dr. Oehler told one guy that requested a longer TOF "If you bring me data showing you have a 50% hit percentage at 9 seconds TOF, we will increase the TOF allowed.
The '89 is battery operated and easy to use. It does, however, require a laptop. It used to require skyscreens - not anymore. Works awesome with a Garmin.
The '89 data is independent of many of the errors that can be found with impact location (Shooter, precision capability of system, cant, AJ, etc.)
It is a bit of an investment, about $3,000, but will do what nothing else affordable does.
I would like to know when the bullet speed is really falling out of transonic range. I thought it would be fun to test and see if these ballistic calculators are really accurate with velocity at distance.
Interesting. Yeah, that's what I wondered. I'll check into AB. Thanks!
Applied ballistics.
How different are the numbers? how different is the final solution between the 2.
Oh, gocha. I was just using the Hornady calculators on their app. Tha basic calculator shows the bullet staying supersonic until between 1400-1500 yards. The 4DOF calculator shows the transition starting around 1200 yards. They both have the same data loaded, but 4DOF uses drag coefficients instead of BC's, apparently. Here are the screen shots.
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In any case, deriving single BC ,for any drag model, from 10 seconds TOF is nonsensical
Unless you are planning on using that data to shoot at a distance where you'll have a TOF of 10 seconds
.I used that example simply to show that, no matter what capability is offered, someone will ask for more.
The best use of deriving a single BC from TOF would be on a radar measured drag function of the same bullet you are shooting. In other words, NONE of the "G" models.
In recent years, there have been a lot of current bullets actually measured on radar. They might be a little different in your system. Measure TOF from your system and, as long as you are operating within the same range as measured, you should be able to adjust your system with precision. Go beyond where they measured and you might be good. Only testing will tell.
Ballistic programs are just like scopes...they have to be sighted in.
CDMs/ PDMs derived from radar records, for most of the small arms projectiles, on TOF scales like 10 sec are also of little use. Spread in Cd vs Mach curves, from shot to shot, deep in subsonic range, for VLD bullets in particular, becomes problem. Therefore sort of BC based on personal "G" model is also problematic. For larger calibers (ie. artillery) that spread is lessUnless you are planning on using that data to shoot at a distance where you'll have a TOF of 10 seconds
I used that example simply to show that, no matter what capability is offered, someone will ask for more.
The best use of deriving a single BC from TOF would be on a radar measured drag function of the same bullet you are shooting. In other words, NONE of the "G" models.
In recent years, there have been a lot of current bullets actually measured on radar. They might be a little different in your system. Measure TOF from your system and, as long as you are operating within the same range as measured, you should be able to adjust your system with precision. Go beyond where they measured and you might be good. Only testing will tell.
Ballistic programs are just like scopes...they have to be sighted in.
There are few, very few radar measurements of 10 seconds. That takes a multi-head, tracking system. Likely only possessed by government labs.
The 10 second limit was set to give "room to grow". When testing into subsonic with the System '89 a target has to be impacted to trigger the microphone to get a reading. Therefore, you can't get good data farther than you can reliably hit the target.
If you can't hit the target, would the data be of any value to you? Probably not.
Lots of advances have happened in the past few years. We now have reliable radar data available from more than one source. We also have a consumer-level device that will accurately measure TOF.
Adjust a radar measured drag function to fit the TOF you measured with your system and you have, essentially, made that drag function fit your system.
Specialized military radars of today. Here are reconstructed CDMs curves for two .30 cal. wildcats tested in France few years ago:
First is for flat base projectile, second for boat tail one.
TOF~12.5 sec and range for VLD is roughly 4000 yards.
10 shots. These were very preceisely manufactured projectiles.
It's normal phenomenon for VLD small arms projectiles in subsonic range what you can see there (and now you do understand what I was saying).Very unpractical shooting distances, but yes projectiles do get tested for various reasons that far.
First is for flat base projectile, second for boat tail one.
TOF~12.5 sec and range for VLD is roughly 4000 yards.
10 shots. These were very preceisely manufactured projectiles.
It's normal phenomenon for VLD small arms projectiles in subsonic range what you can see there (and now you do understand what I was saying).Very unpractical shooting distances, but yes projectiles do get tested for various reasons that far.
I should have specified that I meant very few 10 second radar tracks in the civilian world. I get that there are military (therefore Government) entities that have long range radar systems.
Most of the radar data available to civilians, for civilian bullets, were done by private entities.
Of course. The only point of showing these Cd vs Mach graphs was that for very long TOFs and the long boat-tailed VLD bullets, dynamic instability phenomena are likely to occur below Mach 0.8. Drag increases mostly due to precession and yaw of the bullet, and within the grey blurred envelope there's usually significant statistical split among average drags of individual shots. OTOH, flat base bullet fly subsonically with less precession and more predictable (but they are punished by higher drags levels overall)
