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

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.