GRT 6GT help

[climbing1]

I've tried every which way to get GRT to run on my Mac with various programs, but no joy. Hopefully I'm asking the right questions giving the right inputs.

I plan on living with this cartridge for a while. I'm invested in it, have several more barrels and am not interested in making a change at least through '26. That said, I've tried both N140 and 150 and they both shoot. I'm purely curious what the modeling says is the better choice if I wanted to land on one. Aiming for 90% + fill (alpha and gap) and a 100% (or close to it) burn rate, around 2800 + - . I THINK it's going to be 150, but I'd love to see what the data says if anyone is so inclined. Sorry if I'm missing key inputs, as I haven't got to play around with it, e.g. water volume; I realize these are two different brass brands, but if you're only willing to run one, go with Alpha. Just a general idea from the model vs. real world experience with these powders.

6GT
Alpha & GAP brass
26" barrel
105 hybrids
.060 ish jump

Thank you!

 

[RegionRat]

Jump numbers are a little ambiguous. Without being in a very specific discussion with a standardized reamer, the way we communicate to internal ballistics codes is with COAL (overall length). This value affects the case fill value as well.

You will also need your internal case volume, but unless you are tuning a model with your specific velocity and such, it won't matter much because you will get a rough estimate.

Here is your basic run with your given input set at arbitrary length and for what it is worth. I put Varget in here as well. YMMV