OCW - OBT load development with QuickLOAD

[kelbro]

Just got my new QL upgrade for Windows 8. Lots of stuff added (that aren't in the upgrades) since I bought the first copy 8 or 9 years ago .

Anybody here using the OBT/OCW method of load development? I have used OCW with excellent success in the past. A couple of years ago, I saw a write-up on Chris Long's OBT theory and backed into some of his numbers. My good loads were very (very) close to some of the predictions of his model.

My question for those that have done this... When you plot a couple of charge weights and adjust your powder Ba to make the velocities match, do you permanently change the powder file? I was thinking that you would have to try the new settings on a few loads to confirm your tweak but then you would keep it that way for the remainder of your lot of powder.

I haven't taken it that far yet and don't want to waste the time and effort if it has been tried before unsuccessfully.

Changing bullet weights and start pressures are tweaks that I have done to get the velocities to match but I thought that 10 pounds of powder should perform pretty consistent and that setting could become constant.

 

[Chuckhunter]

Kelbro, I don't personally change the powder file permanently. I just go to file and save the actual cartridge data after the adjustments have been made then I can open that file and all the adjustments will be there and the original powder BA will remain if you want to work on a different combination.

 

[Erik Cortina]

I copied and pasted the powders I use into a new folder called "calibrated powders". Once I make a change, I save it. If I ever play with a new powder, I go to original file, calibrate it, and then save the edited file to the calibrated powders folder.

 

[kelbro]

Kelbro, I don't personally change the powder file permanently. I just go to file and save the actual cartridge data after the adjustments have been made then I can open that file and all the adjustments will be there and the original powder BA will remain if you want to work on a different combination.

Thanks. I've done that too. It's a handy reference. I did not know that it saved the powder tweaks.

I copied and pasted the powders I use into a new folder called "calibrated powders". Once I make a change, I save it. If I ever play with a new powder, I go to original file, calibrate it, and then save the edited file to the calibrated powders folder.

Great idea. I already have a condensed powder file. Creating another powder file would not be an issue. Thanks.

 

[Nomad47]

I do mine in a similar fashion. First I make a new powder file I call "short domestic" as it is a short list of domestically available powders. Then for the powders I use I ADD powders named H4831sc+2%, H4831sc+4%, etc. Then when I'm calibrating a load, I will choose one of those named powders and make minor adjustments to bullet weight, weighting factor, and shot start pressure to get QL to track. I like knowing that the powder I'm using is 2 or 4 or 6% above the default value.

 

[Steve Blair]

My question for those that have done this... When you plot a couple of charge weights and adjust your powder Ba to make the velocities match, do you permanently change the powder file? I was thinking that you would have to try the new settings on a few loads to confirm your tweak but then you would keep it that way for the remainder of your lot of powder.

[br]
No, the effective Ba factor will vary with cartridge and pressure. Use an accurate chronograph and back into the Ba from your recorded velocities. Just make a note in your records of the Ba factor that resulted.

 

[kelbro]

Thanks guys. Got some playing around to do.

 

[Steve Blair]

Here's an OBT node chart. Barrel length down the left side, barrel time in milliseconds across. Note that nodes are "paired" in the chart. This will give indication whether it is worth trying to reach the next node, up or down. If it is one of the pairs, it might be reached. It not, fairly unlikely.

 

[LCazador]

Here's an OBT node chart. Barrel length down the left side, barrel time in milliseconds across. Note that nodes are "paired" in the chart. This will give indication whether it is worth trying to reach the next node, up or down. If it is one of the pairs, it might be reached. It not, fairly unlikely.
[/quote

Ditto on this ! Taking the chrono reading and backing into the ba works well for me , just remember to note the readings .