OBT - Optimal Barrel Time

[Brian in Montana]

I've been messing around a lot with GRT lately, mostly running load simulations, but there's a feature set up to calculate Optimal Barrel Time (sounds like QuickLoads has this feature too). I'd heard of OBT before, but never gave it much thought, so that lead me to do a little googling and reading. It's an interesting concept and seems sound, but seems very technical and particular, got to be very particular about entering the variables.

Anybody use OBT theory in your handloading? What's the outcome been like? Impressions?

 

[cahunter805]

Brian
The concept has been proven to work quite well. Since your program OBT I would be very curious to see some results. It’s supposed to use less rounds fired and time to confirm also.
Have you run an existing proven load from one of your rifles and see how the OBT prediction compares?

 

[Brian in Montana]

Brian
The concept has been proven to work quite well. Since your program OBT I would be very curious to see some results. It’s supposed to use less rounds fired and time to confirm also.
Have you run an existing proven load from one of your rifles and see how the OBT prediction compares?

No. I'm a little slow sometimes and didn't even think of that. I believe I will try it.

 

[WinkB]

If you are interested Erik Cortina has been doing some interesting podcasts. Here is a link to the one he did on Optimum Barrel Time with Chris Long

 

[Brian in Montana]

After wrapping up work, basketball game, and a completely ridiculous HOA meeting, I went to my laptop and plugged in some number into GRT from accurate loads I've developed using a standard ladder test and follow up groupings. I ran the OBT calculations to see if the predicted nodes matched what I'd come up with previously. One was my .308 using 165gn Hornady Interbonds and Varget (about .5 MOA). That one came out pretty close, within about .2gn. I plugged in another from my 280AI - 150gn TTSX and RL23. This one was literally right on the money, exactly. Very interesting. I'm going to keep experimenting with this. Nothing is a sure thing of course, but there does appear to be some validity to this.

 

[Brian in Montana]

Well, there sure seems to be something to this. I shot this group this morning: 284 Win, 49gn of VV N150, 139gn Hornady Interlock BTSP. The group measured .4". MVs from a 5-shot string wheree an average of 2916 with an extreme spread of 8 and SD of 3.



Definitely worth some follow-up.

 

[Brian in Montana]

I tested a load in 280 AI too. It was also pretty darn good, but not quite as good as the 284.