Home Forums Hunting & Shooting Ask The Gunwriters Oehler System '89 (Measuring BC)

I've posted about the Oehler System '89 before. It was announced at the SHOT Show in 2019. There were some bumps in the road but I believe it is mature now and Dr. Oehler told me to go ahead and start talking about it again.

We've done a lot of shooting on this system. We've compared two System '89s simultaneously. We've run the System '89 simultaneously with doppler radar at long range (1,200 yds and more). The results were substantially "The same". The two '89s agreed with each other as much as the '89 agreed with the radar, as much as you'd expect two radar systems to agree.

We've even gathered data on shots at 2 miles. This data matched previous radar data.

We've taken data measured with the '89 and used it to make accurate predictions (1st round hits) on long range targets.

In other words, it is reasonable to believe a properly set up and used '89 will give you the truth.

No, it is not better than a personal drag model that Bryan Litz will create for you when you shoot over his radar. If you had him give you a BC based on established drag functions though, you'd get the same number from the '89 if it was run simultaneously.

The '89 will let you run tests on many different combinations of ammunition and rifles and find out what is the most consistent in YOUR system.

The '89 is portable and powered by batteries.

The '89 gives you two measurements of velocity, reporting the best (longest) measurement and difference between the two, time of flight to the target and BC computed in whatever G function you choose. Want to see it under a different function (say G7 vs. G1)? You don't have to shoot it over, you just replay the test after choosing the new drag function.

It gives you Avg., SD, High, Low and ES of the test.

The most exciting thing about this new technology is that it will generate more questions than it answers. That is where the fun comes in.

This is just as big as, or bigger than, the introduction of affordable, easy to use chronographs.

Things are about to get very exciting!

This is exciting news, especially for long range shooters

Excellent!

My intent was to post two reports from a simultaneous test but they are .pdf files. I tried converting them to .jpg and posting as images but they were not high enough quality.

Does anyone know if we can post .pdf files here?

Thanks.

Edited to say I tried the Forum Help and read about an "Attachment Manager" but can't find any such thing when I try to post.

Bring up the PDF file and then take a picture

Trying PNG files, whatever they are: Edited to add you can go to the image gallery and see them much clearer if you desire.

There was a time, not too long ago, when nobody thought they needed a chronograph. The manufacturer told us what it was.

When chronographs became available, we began to understand that every system could be different. Fast barrels, slow barrels, etc.

It is time to realize that the same is true for drag (BC).

More grooves, less grooves all matter when it comes to BC

Many variables come into play even twist rate

Agreed. Those things could partially explain the gun-gun variation but what about in the same gun?.

The tests I posted were shot with one rifle. Therefore, the same number of grooves and same rifling twist. All the ammunition was from the same lot (even the same 50-round box). Shots 14 and 18 were only 1fps different but .006 different BC. The 85 fps difference between the fastest shot (1037 fps - #12) and slowest (952 fps - #4) showed a smaller drag variance of .004 BC.

Creates more questions than answers.

For example, would repeating the test with faster twist rate give similar results? Would a Micro Groove barrel be the same, better, or worse?

Now that we (average enthusiasts) can actually measure these things a lot of learning is about to occur.

I've watched BC measurements and the one thing that stood out was that the BC was different with each shot. So BC given is an average. Ogival length varies somewhat from bullet to bullet as well

Yep! You've obviously got experience.

Just like watching velocity measurements and they vary with each shot. So, shooters choose the loads that give them the least velocity variation.

Now they can also choose the loads that give them the least drag variation.

I have numerous examples where the drag variation causes more vertical than the velocity variation at longer ranges. In the above example, it becomes a real problem somewhere between 200 and 300 yards. There are rimfire matches that stretch out farther than that.

How much effect does trimming and tipping bullets have on cutting drag variations?

Great question. I have not tested that but believe there are some that have.

A point of clarification, there was an earlier "consumer level" machine that would measure TOF and BC. It was the Oehler M43. It was not wireless.

Not many people were willing to string out 1,000 yards of wire and not many people were working on .22 rimfire at 200 plus yards.

I believe David Tubb had a M43 and he did string the wire out beyond 1,000 yards. I also think he may have made a tool to trim or tip bullets.

If that is correct, I'd call it a "Clue".

Interestingly, the first I heard of plastic tipped bullets having drag consistency issues was (2nd hand) from David Tubb.

I suspect there will be lots of experimenting once people start using the '89.

The tip insert maybe consistent but ogival length also affects BC

I suspect there are multiple things that will be proven to affect BC. This will push bullet manufacturers to make better bullets.

To quote Dr. Ken "You predict what you haven't measured just like you come back from where you haven't been".

As I said earlier, I think this may be as big as, or bigger than, the ability for consumers to measure velocity.

Fun times!

BB if you send me the pdf, I'll see if I can get you a better resolution jpg.
Chris.

Sent to your email, Chris. Thanks.

Here you go;

Thanks, Chris. That makes them much easier to see. I don't know how you did it. My attempts were by using the Image Manager on this site. They looked good there but, when put in a post, were small and fuzzy.

BTW inasmuch as this ammo was subsonic, the downrange mics were clamped to an impact target (piece of OSB). Shot 1 was high, missed the impact target. That is why there is no downrange data for it.

Nice, but anyone know if it will be made available to the general public?

Phil

That's EXACTLY who the system is intended for!

I heard from Dr. Ken recently that Oehler Research had not only begun taking orders on the System '89 but that they had begun shipping.

If you get one and you have questions or issues, hit me up. I was fortunate to be a "Beta Tester" and have quite a few rounds over them.

Shortest test I've done was 100 yards. Longest? Two miles!

I'm very excited to see all that will be learned as more people get the ability to measure BC.

I am lusting after one of these so I can stretch out my 30-06!

I’m wondering if GDT ran into rodent problems as our friend LarryB did when he did similar…it sounds like his polymer tip findings were prescient as Hornady’s “big news” press releases regarding the ELD’s hinted at similar not long ago.

I’m still shaking my head that Dr Ken is putting the capabilities of not even a decade ago Aberdeen Truck and arrays into our hands.

Buford,

GREAT news!

Thanks,
John

His website says the "introductory price" is good thru July 31st. I don't know what it will be after that. Probably still be a bargain for what it will do.

Exciting times.

Yep!

$2485 through July 31.

But here's a question. Suppose I wanted to calculate trajectory at 500 or 600 yards but only had a 200 or 300 yard range. Would the '89 be accurate enough to let a shooter estimate POI reasonably well at 500 or 600 yards?

Measuring short to predict long is not a good idea. The best advice would be to measure the BC at the longest range you expect to need to shoot.

On the other hand, using it at 300 yards (or even 200) to check the consistency of multiple loads would give valuable data. Many shooters will compare 3 or 4 loads for velocity SD. The '89 will let you do that AND BC SD, at the same time.

Yes, the BC changes shot-to-shot, just like velocity. Sometimes, the BC variation will cause more error at long range than the velocity variation.

Many have not known/understood this because they've never been able to measure it.

Most BC that bullet makers give were measured from 100 to 300 yards

True that the farther the distance used to measure BC the more accurate the BC number will be

I'm excited that the product is available and that it should put pressure on bullet manufacturers to tighten their tolerances on bullet characteristics that affect BC, at least for bullets marketed for long range use.

For anyone purchasing/using the system, budget for good meteorological data measurement equipment to use with the system because the atmospheric condition inputs are going to be critical. For instance, a difference of 5 degrees Fahrenheit means a 1% difference in air density if all else is equal, and a 1% error in air density would mean a corresponding 1% error in BC, which could be the magnitude of the shot-to-shot variation in BC we're looking for.

If the instrument used for temperature measurements has an accuracy of +/- 2 degrees Fahrenheit, apparent differences in BC of close to 1% could be errors due to atmospheric condition inputs. Same caution applies to measuring pressure and other inputs AND updating the inputs frequently to make sure the atmospheric conditions are accurate for each shot. Even with temperature readings accurate to +/- 1 degree Fahrenheit, if the ambient temperature increases or decreases 2 degrees over 30 minutes, a BC error of 0.5% or more could result if the atmospheric inputs are not frequently updated.

Measurement techniques (e.g., minimizing errors due to radiant heating of temperature measurement sensor) are important, too.

Probably would be useful to have the meteorological data measurement system set up to freqently record the atmospheric conditions so the BC calcs could be rerun later to make sure the right atmospheric conditions for each shot were used to calculate BC.

If I could sell off a few rifles I'd like to have one at the gun club's range. Probably be the first of the year, wonder if that price will remain the same for awhile?

Phil

Ramblin Razorback is correct about the significance of meteorological data. I believe the instructions mention this, a couple of times. The system uses "station" pressure, temp and humidity in the assumption that anyone willing to go to the trouble of measuring BC would have a means of also measuring these, important inputs.

I don't think it is going too far out on a limb to believe that most will have at least a Kestrel on station.

I remember the instructions mentioning checking temp before beginning any new test.

I don't know what can be done about meteorological data changing during a test. Probably not an issue if doing a 10 or 20 round string. When I've done 100 round strings, it has taken about 30 minutes. So, yeah, it could change if doing a very long string of testing.

All that is taken into account by "good researchers".

Ramblin Razorback's reminder will likely help foster more "good researchers".

Anyone wanting to know what a change in meteorological info does can simply change it and re-play a test.

Good stuff!

Gotta love the collective knowledge of a place like this.

I've heard back from a couple of folks that got their System '89 setup and shot some tests.

One of them also has a System '88. He appreciates the simplicity of the '89 and not having to wait for satellite synchronization. He has long understood the value of measuring BC.

The other said he is surprised at the extreme spread of BC he is measuring. Said it is something he "never could consider before".

He also said measurements with his '89 perfectly explained why one of his rifles needed more elevation than he thought it should have. He had been using a published BC number and a measured velocity. He had to true his velocity to get things to line up. Once he could actually measure BC, he discovered that his rifle/bullet/load had a lower BC than the published number.

He said "I'm now hyper-focused on BC variance". Just like we search for loads with a low SD (or extreme spread) of velocity, we can now search for loads with a low SD (or extreme spread) of BC. His "favorite" load showed a BC SD of about 10%. Time to look at other bullets! (ELR shooters I've been around look for 1% or less SD on BC).

SD and Extreme Spread are not the same thing. Some people put more value in one than the other. I like to measure/report both and let the end user decide which one to pay attention to.

We've gone more than a month with this technology being available and I'm not hearing much chatter about it.

Personally, I've been trying to convince people that the BC shot-to-shot variation can be more significant than the shot-to-shot velocity variation. Of course, it doesn't really matter until you get sufficient distance. I like to think of that as where the velocity has decayed to about 1.2 times the speed of sound.

Dr. Oehler has produced a machine that will measure something most people couldn't measure before. The cost is less than a lot of the scopes people put on their rifles.

The accuracy level is such that it can be used at the shorter ranges of .22 rf. (provided great care is taken in setup).

I had a friend shoot over mine a couple of weeks ago. She used the data and got a 1st round hit at 1,100 yards (6mm Creed). She sent me an email this week that the data we gathered also worked at her home range at 1,200 yards.

I can't be the only one that thinks the availability of this technology is a big deal. To me, it is at least as significant as the availability of affordable chronographs, 50 or so years ago.

I had a very enjoyable chat with a 24HCF member about the Oehler '89 today. He is thinking of getting one and has even gone as far as reading the manual. Imagine that!

He said he is wondering about the utility of the data. Would he gain anything from having it?

Like everything in life, it depends.

When chronographs first came out there were lots of people that realized they would be absolutely no help for shooting 100-200 yards. However, if you want to shoot long range, knowing your velocity and spreads between shots is critical.

The BC chronograph is similar. Shooting centerfire at 600 and less? Nope no help to you at all. Want to shoot to really long range? The data would be very valuable.

If you are a rimfire shooter and shooting 50-100 yds, probably not a lot of value knowing your BC and BC variation. Want to shoot 300 yards? Yep, the data would be very valuable.

There was discussion of the cost of the system. I told him "I have a Nightforce ATACR that cost more". He agreed and said he "Had more than one ATACR".

I've said it before and I'll say it again: I believe this capability is as significant as when normal shooters gained the ability to measure velocity.

Interesting times!

So for the average hunter this will be of no help ?

Yep. The "Average Hunter" probably has no real need to know his true BC number or the variance in BC of given loads. He can likely do just fine using whatever number he finds for his load on the internet/catalog/box of ammunition.

This technology is for those shooters that really stretch things out.

Perhaps I should have put this in the Long Range Hunting section of the forum.

Stretching the distance requires accurate BC numbers. Rifling twist can effect BC with faster twist increasing BC.

Knowing the BC accurately fir your rifles save time and barrel life in my experience

Mr. Boone, just idle curiosity here on my part...I'm not likely to ever shoot at more than three or four hundred yards but I like to know stuff. My question (and it is not my intent to shift the discussion away from Dr. Oehler's machine) is whether BC variances correlate to any other measured parameter, particularly muzzle velocity of individual shots. Can you comment on that?

One comment of my own...long ago, and probably when the 43 was new and talked about more, I learned that BC measurements would be seen to vary from shot to shot and probably caused by shot-to-shot variances in stability. I don't recall the term used at that time but I recall it as "achieved BC."

Think it fair to say that the figure would be ~ 95 % or more. Seeings how only ~ 10% of shooters handload and probably <5% of those shoot any farther than 300 yards.

The longer the distance the BC is measured the more accurate the BC

I've wondered the same thing. Despite shooting a bunch of shots, I have no real conclusion yet. In other words, BC doesn't track velocity. Some shots have low velocity and high BC while some have high velocity and low BC.

Back in the day, I decided I knew what was causing the gun-to-gun BC variance. I just knew it was the crown. So, we started with a good crown and then messed it up. Not only did we prove I didn't have the answer, the damaged crown shot a better group than the "perfect" crown. One of my guys wrote it up in an article that was printed in Precision Shooting. You can read it here: https://www.longrangehunting.com/articles/the-over-rated-crown.670/

My opinion (note I say "opinion") is that many factors affect drag. Twist rate, projectile design, launch dynamics, damage to projectile tips during recoil (rounds in magazine), density of the air you are shooting in, etc.

While I certainly want to know the "why", at this point I've been more concerned with the ability to measure and sort to find what will work best for those I'm associated with. I'm a big believer in what President Regan said: "Trust but verify".

We are in the infancy of TOF measurements being economically available. The more you conduct TOF measurements, the more questions you have.

I'm excited about the questions that will surface when there are 100 people with this capability. I'm even more excited about what will be asked when 500 or more have this capability.

Also, think of what this will do for ammunition manufacturers. Way back, before chronographs, nobody really cared how consistent the velocities were (The SAAMI standard used to be +/- 90 fps). When chronographs became common, the ammunition manufacturers had to pay more attention to consistency.

That is where we are on drag (BC). Once consumers have the ability to measure it, the manufacturers will likely either improve the consistency or face the wrath of internet posters proclaiming how horrible it is vs. one they found that is great.

Yeah, I'm excited. I've been heavily involved in ballistic testing since 1997. Before that, I was a handloader and avid shooter. Perhaps I'm a bit of a ballistics nerd but, hey, everyone has to have something they are interested in.

Maybe you can answer this question. Many bullets are made in forming dies and with use they wear producing longer olives. Bullets made on a screw machine seems would be more identical and have a more consistent BC. Have you found this to be true?

Thanks for your input, Buford. Interesting results.

We know that the drag coefficient of a projectile does depend on velocity, but the nature of that dependence changes with the operating regime, whether sub-sonic or super-sonic. For small variations in velocity, there are other factors that likely dominate, such as the gyroscopic stability of the projectile if that stability is marginal or nearly unstable. Once the SG factor gets up around 1.5, additional rotational speed does not seem to significantly change BC. Factors like tip damage and rifling engraving change the form factor of the bullet, and clearly change the BC of the bullet compared to the undamaged/unfired state. Transient stability behaviour as the bullet leaves the muzzle also affects the drag coefficient. Drag does, indeed, depend on air density, but I would suggest that this is an environmental/external factor and not related to the drag coefficient of the bullet itself.

BC is just a selling point till you go past 300 yards.

[/quote]


Maybe you can answer this question. Many bullets are made in forming dies and with use they wear producing longer olives. Bullets made on a screw machine seems would be more identical and have a more consistent BC. Have you found this to be true?



[/quote]

The worst ES of BC I've ever seen was on some lathe turned bullets. It had an average G7 of .397. In a 10-round test, the low BC was .379. The high was .412. How the hell are you supposed to hit anything with that bullet at really long ranges?

I've also tested some lathe turned bullets that had low BC variance.

Why? I don't know why. Yeah, I'd like to know why.

Only way to know how a bullet performs is to test it.

[/quote]
Thanks for your input, Buford. Interesting results.

We know that the drag coefficient of a projectile does depend on velocity, but the nature of that dependence changes with the operating regime, whether sub-sonic or super-sonic. For small variations in velocity, there are other factors that likely dominate, such as the gyroscopic stability of the projectile if that stability is marginal or nearly unstable. Once the SG factor gets up around 1.5, additional rotational speed does not seem to significantly change BC. Factors like tip damage and rifling engraving change the form factor of the bullet, and clearly change the BC of the bullet compared to the undamaged/unfired state. Transient stability behaviour as the bullet leaves the muzzle also affects the drag coefficient. Drag does, indeed, depend on air density, but I would suggest that this is an environmental/external factor and not related to the drag coefficient of the bullet itself.[/quote]

That has not been my experience in all bullets. Some benefit from higher SG than others. Additionally, velocity only plays a part if the form factor of the bullet is not a match to the standard you are comparing it to.

For example, I've tested bullets that showed a different BC number at two ranges if figured on the G7 curve BUT showed the same number at the same ranges if figured on the G5 curve.

Thicker air requires more spin to be stable. That is why I mentioned it.

[/quote]
BC is just a selling point till you go past 300 yards.
[/quote]

True. I wish I had said it so simply!

Here is another good example of BC not changing IF the system matches the drag model used.

I tested TOF of Fiocchi .22LR Subsonic HP ammunition at three distances, 100, 200 and 500 yards (rounded to nearest 100 yds). Keep in mind that the G1 and G7 numbers are the same shots, just using velocity, atmospherics and distance to calculate it to each standard. That is one of the great things about this system. Although you have to choose a drag function under which to test, you can replay the shots under other drag functions without re-shooting.

Here are the results:

........G1 ... G7
100 .113 .051
200 .108 .051
500 .097 .051

So, the G1 BC changed with velocity but the G7 didn't.

What does that tell me? That the G7 was a perfect fit for this load, in my rifle, despite the shape of the G7 standard not being anything close to the shape of the bullet I was shooting.

Yes, it’s true that some bullet forms require higher SG than others to rapidly damp the transient pitch and yaw as the bullet leaves the muzzle. The SG=1.5 figure is just a rough generalization.

Note that I mentioned velocity versus drag, not BC. Drag always depends on velocity, but as you pointed out there are various standard form factor models which model the drag-velocity relationship for different form factors. If your projectile’s form factor perfectly matches the form factor of the standard model, then the model will correctly predict drag through the velocity curve, and the BC will remain constant for a given velocity regime (sub-sonic, trans-sonic, super-sonic). The drag relative to a model remains constant, but that doesn’t mean that the bullet’s absolute drag remains constant.

Again, thanks for reporting your results. Very interesting!

Dr. Oehler is amazing !! I talked to him years as I tried to understand 22 Rimfire problems. I thought & still believe that bullet wobble affects rimfire flight & varies some from lot to lot & bullet to bullet. T

I think you could look at the Standard Deviation of BC to explore your theory. "Wobbling" bullets would have more drag and, I'd think more inconsistent drag.

I've got one of those 1:9 barrels for a 10-22. I plan to do some testing to compare to a 1:16 barrel.

Circling back to see if anyone else has begun to measure their BC numbers.

Since I first understood that BC shot to shot variability is similar to velocity shot to shot variability I've thought it something important for long range shooters to measure.

Bryan Litz has done a wonderful job of measuring actual performance for shooters at those events where AB radar has been present. That radar can't be everywhere, though. Like Parshal said, if you don't have regular access to AB doppler, the '89 is the next best thing.

I've run an '89 right next to the AB radar, measuring the same shots. The numbers agreed as much as you could expect two radars to agree.

I also posted the above in the Long Range Hunting forum. Since Rick Jamison did a Handloader article on the '89 I thought I'd post here as well.