How to add a new powder to GRT

@414gates @414gates 7 months ago

I want to add B12.7 to GRT.

I've used the data from VV 24N as an entry point.

What is the process to true the powder data against measured velocity.

Google says :

Steps to Add a New Powder in GRT:
Generate Data: Perform a 2x2x2x5 development run (2 calibers, 2 bullet weights, 2 charges, 5 shots each) over a reliable chronograph.
Input Data: Open GRT and input your specific load data, including accurate bullet measurements and case volume.
Use OBT (Optimal Barrel Time): Use the GRT OBT tool to match the pressure curve and burn rate to your actual measured velocities.
Save as New Powder: Click on 'Create grt load file' after the OBT simulation produces accurate results to save the new powder in the user section.

I just want confirmation that the method works as advertised.

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@T @tripodmvr

Those steps are the burn rate calibration OBT process for your specific rifle. The propellant might burn faster in your rifle and you can then store that result as "30-06 N550 165Hornady OBT load" or something similar. You can then choose that propellant when reloading for that rifle and it will give better simulations with other bullets.

To add a new propellant you need to create a powder file with the thermochemical data as can be seen in the window below your chosen powder. I have heard that there might be a way of importing QL files and will look into that.

@414gates @414gates OP

I found this posted on Jaracal in 2021 :

"Somchem 12.7-0","3600","1.2483","1.596","0.3018","0.8074","0.439","1.5538","0.950","","","","","","","","","","","",".330"

If I use those numbers in the following places in GRT, it looks close to actual.

@T @tripodmvr

The info I have in QL is exactly the figures above. I have previously invited you to send me data and I will gladly help with the BMG calcs to guide you. I am unsure of the GRT values as they differ substantially with QL. How did you get the figures into GRT?

@T @tripodmvr

Herewith conversion method for powder files - QL to GRT as from AI.

Powder Name: [Enter here]
Manufacturer: [Enter here]
Ba (burning rate factor): [Enter here]
Density (g/cm³): [Enter here]
Energy (J/g): [Enter here]
Temperature coefficient: [Enter here]
Notes: [Optional – e.g., source QuickLOAD v3.9]

Step‑by‑Step Workflow: QuickLOAD → GRT
1. Gather Powder Constants from QuickLOAD
Open QuickLOAD and locate the powder you want to transfer. Write down these key parameters:

Ba (burning rate factor)

Density (g/cm³)

Energy content (J/g)

Temperature coefficient (if available)

Powder name and manufacturer

QuickLOAD usually shows these in its propellant database window.

2. Open GRT Powder Editor
Launch GRT.

Go to Database → Propellants → Add/Edit.

Click New Propellant.

3. Enter the Data
Fill in the fields with the values you copied:

Name: Exact powder name (e.g., “Somchem S335”).

Manufacturer: As listed in QuickLOAD.

Ba: Burning rate factor from QuickLOAD.

Density: Enter in g/cm³.

Energy: Enter in J/g.

Temperature coefficient: If QuickLOAD provides it, copy here.

4. Save and Test
Save the new propellant entry.

Create a test cartridge setup in GRT using this powder.

Compare predicted velocities/pressures with QuickLOAD outputs for the same load.

5. Calibrate with Chronograph Data
Fire a known load with this powder.

Input your chrono results into GRT’s calibration tool.

GRT will adjust the constants slightly to match your real‑world data.

@414gates @414gates OP

How did you get the figures into GRT?

The display fields are editable, I just changed them.

The reason I did not take you up on your offer yet, is because up till now, even if I had the perfect load, I would not be able to shoot it.

To be able to see what the difference is between component changes means you need to be able to shoot the difference.

I'm still getting there. I had made incremental changes to the platform, each of which showed a bit of improvement on paper, and I've made one more now that needs testing.

I've also changed the scope, the original scope had to go in for repair. It will be truly amusing if the SH4J manages to preside over better results than the IOR.

As for components, I've worked my way through 4 powders, 5 bullets, and two primers, I'm still about 80 testing rounds away from the bullet I will standardise on, which is between the two weights of bullet I've been testing.

The reason for the different powders is availability. If I ever need to load for an event, and one powder is not available, I can choose between several others.