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