Gordon's Reloading Tool - how do I get it to work ?

[Martin52]

I use a MacBook Air with macOS Catalina version 10.15.7 and am having difficulties getting GRT to function.

GRT is downloaded to a USB.

I have installed trial versions of Windows 10, Parallels Desktop and Crossover to see how these go before buying.

One thing I come up against is a message saying Airport Utility won't open the file.

Would appreciate any suggestions.

Martin

 

[divingin]

Do any other Windows apps run? or do you get the same Airport error message?

If they do, make sure you're trying to run the GordonsReloadingTool.exe file in the GRT folder.

If other apps don't run, there's likely something misconfigured in the MacOS tying to the windows memory partition. Can't help with that, sorry.

 

[Jager]

I run a MacBook Pro on 10.15.7 and run a Parallels/Win7 partition so I can access QuickLoad and a few other Windows-only apps. Works fine.

Airport Utility is an old (deprecated?) app for managing legacy Apple Airport WiFi routers. It has nothing to do with GRT or Parallels. That you're getting an error message from it suggests something amiss.

Do what divingin suggests.... get Windows working first. Make sure you can boot into it, that you can navigate around in that environment, that shortcuts and programs fire off when you double-click them, and that shutting down Windows and closing Parallels works as expected. Once you're at that point, it should be pretty straightforward getting GRT to work.

 

[Martin52]

Got it working, thanks. Opening Windows 10 first and then opening the GRT exe file made the difference. I stored GRT on a USB and also tried it on my son's PC with Windows as the operating platform and it started up straight away. I now understand the Mac' workaround' but at first it was a little tricky.

After inputing the load, bullet and case data, am I right thinking the objective is then to align the "Bullet Lead Time 10% pmax' with the 'OBT ' in the right hand panel of the screen to be as close as possible to a node? Then test on paper.

 

[jelenko]

Martin - It's best to first fire ~ 10 rounds over a chrongraph with the powder and bullet you plan to use and use these results to allow GRT to tune the powder parameters to your rifle. You enter the observed results in the to results tab.
Making sure to measure the actual lengths of the bullets you are using and the water capacity of a fired case and input these measurements into GRT, you run the 'OBT' function to get a GRT file that's calibrated to your rifle. From the same OBT window you can have it calculate the powder load for each of the optimum bullet times.
The guy that narrates the video below develops loads for clients. In his experience, GRT/OBT correctly predicts 60% of the time => 40% of the nodes predicted aren't nodes. His suggestion is to try an 'adjoining' node. My own experience tracks those %'s pretty well.
If you don't do the work to calibrate GRT to your rifle, the nodes predicated usually don't work out.
Here's youtube on using GRT.

Good luck!

 

[Martin52]

Martin - It's best to first fire ~ 10 rounds over a chrongraph with the powder and bullet you plan to use and use these results to allow GRT to tune the powder parameters to your rifle. You enter the observed results in the to results tab.
Making sure to measure the actual lengths of the bullets you are using and the water capacity of a fired case and input these measurements into GRT, you run the 'OBT' function to get a GRT file that's calibrated to your rifle. From the same OBT window you can have it calculate the powder load for each of the optimum bullet times.
The guy that narrates the video below develops loads for clients. In his experience, GRT/OBT correctly predicts 60% of the time => 40% of the nodes predicted aren't nodes. His suggestion is to try an 'adjoining' node. My own experience tracks those %'s pretty well.
If you don't do the work to calibrate GRT to your rifle, the nodes predicated usually don't work out.
Here's youtube on using GRT.

Good luck!

Thanks, I have some recent data for one of my bullet weights from a friend's Labradar that I will input.

The video gives a good explanation.

Thanks
Martin

 

[Martin52]

Good to know that adjusting the Burn Rate Factor (Ba) allows you to change the GRT predicted velocity to be the same as the actual velocity inputted into the Measurements tab along with the corresponding powder charge, before doing the OBT adjustment.

 

[jelenko]

Just keep in mind that even people who are highly experienced with using GRT find ~ 40% of the predicted nodes aren't accurate loads.

 

[Martin52]

Yes, and that seems particularly true for the half nodes.

 

[dstoenner]

Just keep in mind that even people who are highly experienced with using GRT find ~ 40% of the predicted nodes aren't accurate loads.

I agree completely. The only ones that seemed reasonable where for the 30-06 and 6x47 Lapua. 223 is all over the map.

i have gone to just using it to get an idea of chamber pressure for a load sequence and the the good points.

i guess we are getting what we pay for. OBT is only useful as a curve fitting the data.

David

 

[jelenko]

In my working with GRT, I've found just over 50% of the predicted loads are close enough for some 1/2 MOA groups. Since I'm testing from prone with a sling, I'm probably not the most discerning user.

 

[danny]

In my working with GRT, I've found just over 50% of the predicted loads are close enough for some 1/2 MOA groups. Since I'm testing from prone with a sling, I'm probably not the most discerning user.

Well,
Since you are using a sling, I think that you are a pretty discerning user. With that said, if you can suffer a rest during load development, it may help.

Danny

 

[Martin52]

.....i have gone to just using it to get an idea of chamber pressure for a load sequence and the the good points.

Yes, useful/informative for that too.

I found my current 155gr loads are ~ 58k psi, so towards the upper end but still slightly below the upper node estimated in GRT of ~59-60K psi.

My 185 Juggernaut load (44.2gr Varget, 2750 fps) is over pressure although a 32 inch barrel would be OK. The lower node should give me about 2650 fps.

 

[Martin52]

Martin - It's best to first fire ~ 10 rounds over a chrongraph with the powder and bullet you plan to use and use these results to allow GRT to tune the powder parameters to your rifle. You enter the observed results in the to results tab.
Making sure to measure the actual lengths of the bullets you are using and the water capacity of a fired case and input these measurements into GRT, you run the 'OBT' function to get a GRT file that's calibrated to your rifle. From the same OBT window you can have it calculate the powder load for each of the optimum bullet times.

A few weeks on with GRT and one question, after entering the chronograph data in the measurements tab, depending on the powder/projectile combination, the average velocity shown in the measurement tab can show a variance to the predicted velocity. Do you adjust the pressure tab (250 Bar) up or down to get the GRT predicted speed to match the recorded speed then run the OBT ? This can be done by adjusting the K and Ba numbers, I am not sure which way is correct.

 

[jelenko]

Great question!
In watching the the most recent how to videos on GRT, the speaker is suggesting to let GRT calibrate itself by simply using the 'OBT' function.
To do that, first put the amount of powder you used in the test rounds into the "Powder mass" value. Then, just click on the OBT button. When the OBT screen appears, it should show the average velocity for the test rounds that were entered on the Measurements tab [provided you entered the charge weight in the Charge column. You'll need to enter the distance the chronograph was from the muzzle. If using Magnetospeed or LabRadar, you enter 0.
Then, click on the Compute OBT and charge adjustment - note the "automat. calibration" - GRT automatically calibrates the powder parameters based on the observed velocities with the powder charge weight.

Doing this opens a new window with the powder calibrated and you it will calculate the needed charge weight to be at one of the nodes - which you can also select.

You can have GRT save this view with the calibrated powder - the 'button' is at the bottom of the screen.
Once you do that, you can have GRT predict changes in powder charges if the temperature changes.

 

[Martin52]

Jelenko,

What threw me off track was the comment at 6:52 in this video:

You will see the initial pressure is adjusted from 250 Bar to 400 then back down to 375 in order to change to GRT predicted velocity to align as closely as possible with the actual velocity entered in Measurements - and this is done before running OBT. I have been doing this in my modelling where the actual average velocity varies from the GRT predicted velocity.

At 11:45 there is a comment about the initial pressure (load 53.26gr ) being too high to calculate BLT however it goes on to say the selected load is even higher at 56gr.

Still thinking this through.

Martin

 

[Martin52]

On further thought, changing the initial pressure (as described in the above video) in order to change the predicted velocity to equal measured velocity appears to be a calculation that is independent from the OBT calculation that uses the measured, not the predicted, velocity. As such, any change in initial pressure when comparing the predicted velocity with the measured velocity is not relevant to the OBT calculation.

Have I got that right ?

 

[jelenko]

In earlier how to videos they showed calibrating GRT by adjusting the initial pressure. I've done that and had success with some loads/nodes.
In the video above, Cassie also uses the default Initial Pressure and uses GRT to do the calibrating. I've had more success letting GRT do the calibrating vs me adjusting the IP. From the video it seemed like he was saying that either way would work but, sometimes, adjusting IP would not. I do use GRT to get an idea of an appropriate load range before I make up test rounds.

Note that he says, in his experience, ~ 40% of the predicted nodes are not accurate loads.

 

[Martin52]

When the default IP of 250 Bar and predicted velocity remains unchanged and with measured velocity included, OBT will compute and provide a node.

If the IP is then changed to align the predicted velocity with the measured velocity OBT calculates a different powder charge, speed, pressure - for the same node.

Moving to the next stage and testing these results on paper sometime over the next month.

 

[kiwijohn]

Just on the subject of GRT in general.
I have had to "design" a 6.5 06 AI case and chamber to get any reloading info on that cartridge, I cant get the "effective cross section" function so I have taken an average of some other 6.5 case performances.
Any clues / hints would be appreciated.

It would be better if it had the 6.5 06 or its Ackley Improvement but they dont hence the work around.