Gordon's Reloading Tool

[GuitarmanNick]

Not sure if anyone has posted about this yet, but this is a great open source tool for anyone that reloads. I have no experience with Quickload, but from what I have read, this appears to be a free substitute.

When I entered the data for the couple of loads that I have worked up myself without any data with which to start, it appears that both are near the maximum pressure with 100% burn rate. My brass for these loads shows no signs of over pressure and are very accurate.

As I begin to set up to load 7.62x39mm for my SKS and a .223 for a 10.5" AR pistol, this tool should be very helpful in producing the results I seek.

Curious to see what the more experienced loaders think of GRT.

You do have to create an account and login before downloading the tool or updates. It would be a good idea to change the generated password to something you can remember for downloading any future updates.

 

[jelenko]

Over on usrifleteams there is an extended thread on evaluating GRT.

To get good congruence with on target results, they are finding that you need to input to GRT what your actual velocity is for an actual actual charge weight [e.g., for one of my loads, GRT was about 100 fps different than magnetospeed measured], measure the actual H2O capacity of your cases, and measure the actual length of your bullets [GRT's length for the bullet I am using was off by several hundredths]

After I inputted my data, GRT predicted the accurate loads I've found via ladder testing within .05 grains.

I haven't used GRT yet to predict an accuracy node and then test to see if it actually is.

FWIW, GRT ignores the type of action used - only the barrel length, twist and bore diameter.

 

[dstoenner]

Over on usrifleteams there is an extended thread on evaluating GRT.

To get good congruence with on target results, they are finding that you need to input to GRT what your actual velocity is for an actual actual charge weight [e.g., for one of my loads, GRT was about 100 fps different than magnetospeed measured], measure the actual H2O capacity of your cases, and measure the actual length of your bullets [GRT's length for the bullet I am using was off by several hundredths]

After I inputted my data, GRT predicted the accurate loads I've found via ladder testing within .05 grains.

I haven't used GRT yet to predict an accuracy node and then test to see if it actually is.

FWIW, GRT ignores the type of action used - only the barrel length, twist and bore diameter.

All of the above is 100% correct, but doing that is still not treating you rifle chamber, barrel, powder, cartridge and bullet as a system. You need at least one group of velocity results. Then run an OBT run. It will find a node that is the closest to your sample velocity. Then have GRT create that OBT run onto a separate file. What you will notice is that 2 of the powder parameters get much more levels of precision. If you copy and paste those values back to your original file then it will start predicting you system values even more accurately.

I have been working with this tool over the last 6 months and it is good. I still do not have perfect predicition but at least it shows you where to hunt for a good node.

But for free( for now) it is a BARGAIN.

David

 

[jelenko]

2 of the powder parameters get much more levels of precision. If you copy and paste those values back to your original file then it will start predicting you system values even more accurately

Ah!
Thanks!

 

[jelenko]

copy and paste those values back to your original file

Why not just use the obt file and run OBT on it?

 

[VA_XTC_Shooter]

I was part of the group on usrifleteams that worked with GRT for a bit. As mentioned in another thread, I still have my doubts, it has its limitations.
I am also not convinced the OBT is settled and totally ironed out.

 

[dstoenner]

Why not just use the obt file and run OBT on it?

You could but then you would loose the powder level and velocity for the node of interest. But actually i could only get correlation on my 6x47L and 30-06. 223 never hit a node and a nice tight group at the same time and/or the nice low sd/es.

after spending 6 months trying to get OBT to work i gave up. It is good for predicting chamber pressure so that is all i use it for. Checking the pressure for which one of the ladder loads gave me the best group with good es

David

 

[dstoenner]

I was part of the group on usrifleteams that worked with GRT for a bit. As mentioned in another thread, I still have my doubts, it has its limitations.
I am also not convinced the OBT is settled and totally ironed out.

I agree completely on OBT. It can’t get there.

 

[Sumtoc]

Have read most of the posts and watched the videos re: GRT. It's disappointing to see that it doesn't work well for .223. Is this because of the smaller capacity and overall more sensitive to small changes?

Working up loads for a buddy's .223 F Class rig and will be shortly doing the same for my new 223 (we like a challenge). So would really like this to work to shorten the test process and save a bit of reloading mats.....

 

[jelenko]

No question GRT/OBT nodes is not 100% accurate in it's predictions even with all the inputs measured accurately. In fact, in an instructional video, the instructor mentions that in his experience, GRT gets the node wrong about 40% of the time.
That said, in using it over the past year [across 26 and 24 inch barrels, 5 different powders and 4 different bullets], I've found, with 223, GRT to predict a node within +/- 0.2 gr about 80-90 % of the time. If you don't allow the +/- 0.2 gr as 'hitting', my experience is very close to 40% of the predictions are not nodes. There have been times when the node was more than +/- .2 grs and could be far enough away it was just easier to do a ladder over a grain or so.

 

[Beiruty]

I am having great succes using GRTools fir load development.
I can predict MV with less than 1% error
Here is new video I just posted yesterday.

 

[SeabeeKen]

I've had excellent results with GRT and OBT also. In fact, I took a number of my tightest shooting loads developed normally and measured velocities and ran them. In each case OBT recommended <.1 gr powder adjustment to hit the node, and in several cases .02 gr. As Gordon says, garbage in, garbage out. Measure everything. I've had better results with GRT than Quickload. They both are just simulations.
As for OBT changing the powder values, you should be able to open the powder model, click new with copy and enter the adjusted values and save it as a user defined powder for that particular rifle. In a few other tests, I would do a ladder until I got extractor marks and the simulation showed i was over 70,000 psi so by the time we see these signs we are well over pressure. IME

 

[kiwijohn]

I use it and have found the velocities fairly close but usually over predicted and overpressure.
I would like to see a simple way to adjust pressure / powder volume to match the chrono information.
It does get within the 1% factor as it stands though.

 

[Beiruty]

I use it and have found the velocities fairly close but usually over predicted and overpressure.
I would like to see a simple way to adjust pressure / powder volume to match the chrono information.
It does get within the 1% factor as it stands though.

1) Make sure that you measure the H20 water capacity of your cases, min of 5. Use the average value in GRTools.
2) Use Labradar or Magneeto for MV
3) My results are less than 1% away from actual MV.
4) I tune Ba to match the MV using a spreadsheet I developed.
5) You may tune your the case capacity if you did not do 1) above.

GRT MV vs MV Greg 3006 180 VLD Elite Hunting.xlsx

1drv.ms

 

[jelenko]

The 'OBT' function automatically tunes the powder to your observed velocities. It modifies Ba and k.
After you run the OBT function with the observed velocity the % that Ba and k are modified is shown on the resulting screen.
You can save the results of the OBT function - GRT saves it as 'your file name'-obt.grtload.
You can save the 'obt' file. You can change the temp in the obt file to see the effects of temperature changes.

 

[Beiruty]

The 'OBT' function automatically tunes the powder to your observed velocities. It modifies Ba and k.
After you run the OBT function with the observed velocity the % that Ba and k are modified is shown on the resulting screen.
You can save the results of the OBT function - GRT saves it as 'your file name'-obt.grtload.
You can save the 'obt' file. You can change the temp in the obt file to see the effects of temperature changes.

This Calibration method is also, one click method.

 

[Beiruty]

Not sure if anyone has posted about this yet, but this is a great open source tool for anyone that reloads. I have no experience with Quickload, but from what I have read, this appears to be a free substitute.

When I entered the data for the couple of loads that I have worked up myself without any data with which to start, it appears that both are near the maximum pressure with 100% burn rate. My brass for these loads shows no signs of over pressure and are very accurate.

As I begin to set up to load 7.62x39mm for my SKS and a .223 for a 10.5" AR pistol, this tool should be very helpful in producing the results I seek.

Curious to see what the more experienced loaders think of GRT.

You do have to create an account and login before downloading the tool or updates. It would be a good idea to change the generated password to something you can remember for downloading any future updates.

You can also use the "gas-hole" leak feature to model your semi-auto too.

 

[jelenko]

You can also use the "gas-hole" leak feature to model your semi-auto too.

Caution. My understanding is using the gas hole over compensates because it assumes the hole vents to the outside vs to a small tube.

I tried using it with my AR and got 'wonky' results.
All my other results have been without a 'gas hole' in the barrel.

 

[kiwijohn]

The 'OBT' function automatically tunes the powder to your observed velocities. It modifies Ba and k.
After you run the OBT function with the observed velocity the % that Ba and k are modified is shown on the resulting screen.
You can save the results of the OBT function - GRT saves it as 'your file name'-obt.grtload.
You can save the 'obt' file. You can change the temp in the obt file to see the effects of temperature changes.

OH thats good, I thought it just sorted the observed MV that you got via Chrono. Still makes my loads look too hot. ( they probably are )
I will look a little closer next time I adjust the Velocity on OBT.

As said I am getting within 1% of the predicted data, but 1% is still 30 fps on most rifles.

 

[jelenko]

I think there's GRT documentation that says their simulations are within 5%. I think of it as a tool that, usually, get's me in the neighborhood quickly. Sometimes it lands me at the right address; other times I still have to find the right address.