Gordon's Reloading Tool

A

Aguila Blanca

Staff
Special warning notice

CAUTION: The following post includes loading data that the powder manufacturer data indicates will be 14% above +P pressure. It may not be that high in YOUR gun, but you USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.


Has anyone been using Gordon's Reloading Tool?

Two recent/current threads dealing with seating depth and pressure led me to download a fresh copy of GRT and take a look at it to see if might be a decent predictor of pressures. It has calculations for it -- the question is how accurate they are. GRT now includes Hodgdon HP-38 (which is the same as Winchester 231), and that's my powder, so I can compare to real world results.

And what I got on a trial run was not even remotely related to what I found in the real world, and what Shooting Times found in the real world.

For perspective, a couple of years ago I realized that EVERYONE at the club where I hoped (before my hip went bad) to be shooting IDPA was shooting 9mm. My play guns (and my carry guns) are 1911s, in .45 ACP. So I set out to come up with a .45 ACP load that's equivalent to 9mm. And Shooting Times had the answer -- a friend sent me a link to an article of recoil vs. bullet weight. The author conveniently used two Berry's bullets (the same two that I have), and Winchester 231 powder. And one of his loads was 5.3 grains, which happens to be what I get from one aperture on my Lee AutoDisk powder measure. The author loaded to 1.24" C.O.L. and I load to 1.25" -- not a huge difference.

So I have reported, real world velocities for both bullets, over 5.3, 5.7, and 6.1 grains of the same powder.

Then I ran those same loads through GRT (except that I neglected to change the C.O.L. from 1.26" to 1.24"). The results were a shock, especially considering that the discrepancies would be been worse if I had used the correct C.O.L.

For the 230-grain bullet, Shooting times reported velocities of 724 fps for 5.3 grains, 783 fops for 5.7 grains, and 869 fps for 6.1 grains. That velocity for 5.3 grains is not far from my chrono results. BUT ... GRT came up with 863 fps, 900 fps, and 935 fps, respectively. And GRT reported that the first two were near max pressure and the third was over-pressure.

For the 185-grain bullet, Shooting Times reported velocities of 687 fps, 762 fps, and 812 fps. GRT calculated 942 fps, 984 fps, and 1024 fps.


Consequently, I'd like to know if anyone else has used GRT and had real-world numbers to use for a comparison. I didn't expect the calculated results to be exact to three decimal places, but these numbers are off by a factor of 15% to 37%. The average for the six samples was 22.33%. Am I being naive in thinking it should come closer than that?
 
I have been using GRT on several loads. The measured speeds are very close to the simulated results, except loads using Ba9, in which case I believe the powder model is questionable. It is a good tool (good enough for me). The modeling they use is as good as, if not better than, the competition. What's lagging is powder models and it is getting better every release. They actually ask users to submit their results to aid their powder model development.

I like what they are doing, so I support them through patreon. They deserve our supports.

-TL

Sent from my SM-N960U using Tapatalk
 
Powder model could be the #1 reason. For me all the loads I have with Vectan Ba9 are off.

They may have added a powder model in their update. But sometimes that model is preliminary, and they have indication of model maturity.

Another thing is the bullet type. They model cast bullets having the highest friction. My experience is the other way around. Plated bullets have the highest friction, followed by jacketed and cast.

You can report your measured results to them. But that requires measuring the case capability and using jacketed bullets.

-TL

PS. I just check hp-38 powder model. It is not very mature yet. It may need adjustments. I suggest you submit your results. Also you may want to measure your case capability.

Sent from my SM-N960U using Tapatalk
 
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I’ve seen several people say that QuickLoad and GRT are both rather poor at predicting straight wall cartridges without some fine tuning. They are much better at bottle cartridges.

They also aren’t good with small case fill percentage.

My handgun loads with QuickLoad and GRT for 45ACP are both within about 5% of velocity, but GRT does overpredict pressure compared to QuickLoad for that powder (Accurate #5) and according to reload manuals. GRT overpredicted velocity by 5% and QuickLoad under predicted it by about 5%.

My 5.56 (Accurate LT-32) and 308 and 3006 (H4895) loads seem fairly good except I’m using my own tuned powder model for LT-32 so that in itself is a tuning knob. I submitted some files with my load and chrono measurements for Accurate LT-32 so that GRT can work on a powder model and hope they get it closer with algorithms than mine did tweaking the variables manually.

QuickLoad doesn’t have an LT-32 model either. But the QL comparisons I have with H4895 to GRT are good... in some cases spot on, like 308Win measured average 5 shots 2705 FPS SD 14FPS, GRT 2713 FPS, QL 2710 FPS.

There are a lot of variables in play.


Andrew - Lancaster, CA
NRA Life Member, CRPA member, Calguns.net contributor, CGF / SAF / FPC / CCRKBA / GOA / NAGR / NRA-ILA contributor, USCCA member - Support your defenders!
 
lordmorgul said:
I’ve seen several people say that QuickLoad and GRT are both rather poor at predicting straight wall cartridges without some fine tuning. They are much better at bottle cartridges.
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FWIW, I sent the data to GRT, as they request, and someone got back to me very promptly. The response was courteous but, IMHO, a bit defensive.

First, he (I assume it was a he) confirmed that GRT isn't as good for straight wall handgun cartridges as it is for bottleneck rifle cartridges. The part that bothered me was when he then went on to lecture me about hos GRT can't be completely accurate compared to real world result because ... yada, yada. Yeah, I know that, but I think a 37% error is a wee bit excessive. He conveniently zeroed in on the one result that was only off by 8% and used that to justify the discrepancies as acceptable.

I'm not satisfied with the response, but I'm not going to engage in an e-mail argument. They asked for input; I provided input. If they want to use it to fine tune GRT, good for them; that's why I provided it. If they want to ignore real world results, it's their loss. Until GRT can do a lot better than a 37% discrepancy for cartridges that I load, I won't consider becoming a Patreon sponsor.

Here's the text of the reply I received:

the short answer would be: "its a simulation, not a emulation", but that would explain nothing, so before i explain, let me ask you some questions:

1. how much can be the lot-to-lot deviation of a propellant?
answer: up to 10% in pressure

2. how much can be the deviation of different chronographs?
answer: up to 3% in velocity

3. how much can be the velocity/pressure influence of your particular gun chamber, barrel wear, cylinder gap of revolvers, primer, load accuracy, crimp, bullet manufacturing tolerance, ambient temperature, humidity?
answer: up to 20%

..and so forth, you get the idea

So, how can it be in hell happen that a simulation can predict absolutely accurate numbers? ...it can't! the simulation is just a simulation of a "theoretical gun chamber with barrel and bullet". Without correct user input and measurements it is impossible to get usable results. In general, a deviation from the reality with this type of equations of 10% is rated as "good", 5% as "very good" and 3% or below as "excellent".

GRT predicts in most cases with a good developed powder model (bar-graph in the high green area) 3% or less on rifles. On pistols it is a different story, why?

On pistols the cartridges usually have way less propellant used. Less propellant means less overall energy and all other things that "steal" energy like gas sealing, gun mechanics, chamber and so forth have just WAY more influence on the combustion process than on rifles, where the ratio is much smaller.

Additionally a small deviation in the load process of pistol cartridges, e.g. OAL or charge/bullet weight can have a WAY more influence on the combustion process than on rifles because of the reasons mentioned above. Thus these pistol cartridges are often produced on progressive presses with theyr own deviations and tolerances. Just change the OAL or the powder charge slightly and you see what effect it can have.

The question is: how good have you measured, have you entered the REAL bullet length and the REAL fired(!) case volume for your simulation? Have you tried a different gas sealing/friction model if you use e.g. soft lead bullets? On which chronograph was the measurement taken? e.g. if i measure one with Chrony or something similar it says 860 fps, with MagnetoSpeed it says: 902 fps, Labradar says 897 fps (side note: we use Labradar and MagnetoSpeed for that reason).

The powder you choose is currently in the "mid range" of its developing process, indicated by the colored bar graph of each powder model in the database window. The powder models of GRT are continiously updated, based on real world measurements, also including pressure. if you have real world measurements of velocity, you can contribute your measurements for check and improoving the models by our lab. For that you can upload your measurement files directly to our Lab using the GRTLab-Plugin shipped with GRT.

Last but not least back to your results:

you said with the 230 grain bullet you have 869 fps for 6.1 grains and your GRT simulation says 935 fps. That is a deviation of 7.1% [AB note: the deviation is 8%, not 7.1%] after reading the explanation above, how bad do you think is the result realy?

i choosed the higher charge because of the energy content, with lower charge you will see it gets worse, also if you use a slower powder which results in a bad burn-rate (in example). you have to know that below 90% will add additional error to the results.

but even if the deviation is 10% in your example, i would suggest you to look again over the input values, and yes you have to enter and calibrate the observations to the simulation if you want better results.
In the first step you adjust the Initial Pressure (IP) value to calibrate your local reality to the simulation. Even with the fact that OBT makes no sense for Pistols, you can use that OBT-Tool in GRT to calibrate your powder model to your specific gun and setup and save that for future use.

you can share this answer with others that have this question. Let me know what you found out after further investigation of your own loads and your simulations and please share your measurements.
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Failure to address the bigger deviations is a significant omission. His 7.06% vs your 7.59% is because you calculated the percent by which the prediction exceeded your measured value, while he calculated the percent by which the measured value was smaller than the prediction. In other words, you made 869 fps the 100% value, while he made the 935 fps the 100% value. You gave the prediction's error relative to your gun, while he gave your gun's error relative to the prediction.

Obviously, your approach makes more sense in this context because reality rather than a modeled estimate is what matters, in the end.
 
I wouldn't like it if I were to receive similar answer to my question. It sounds really condescending. It is bad on them.

When I come to think about it, all the good loads I have had with the tools are rifle rounds with good load ratio. I just test a load of 7mm Mauser. 2080fps simulation, 2065fps measured. It is pretty good. A week ago a fellow from France did a super light load 30-30. It was off by more than 20%. The model couldn't account for the incomplete combustion of the powder under that condition. Finally the loads I have with Ba9 are 9mm and 40 s&w. That sort of shows the limitations of the tool.

To be fair, QL seems to have similar limitations. The fellow from France was using QL. I checked his load on GRT and got almost the same results.

I use simulation tool daily at my day job. The first thing we learn is simulation has limitations. The first thing we look for at test results is how well it match our simulations, not how well it meet the specs. When we see discrepancies, we try to find the cause. Sometimes we simply can't explain the difference, then we have to accept it and shift our designs to compensate for it.

I guess that may be the way we have to work with the tool. Good thing the tool seems conservative. It gives a safe starting point for us to work up the load.

-TL



Sent from my SM-N960U using Tapatalk
 
tangolima said:
I guess that may be the way we have to work with the tool. Good thing the tool seems conservative. It gives a safe starting point for us to work up the load.
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Yes, at least the errors/discrepancies are on the side of safety. That's certainly true, and I would not want it to be the other way.

My little venture into GRT came about as a result of two different threads here asking about the effects of seating a bullet deeper than called for in publish loading data. In those threads I proposed a quick-and-dirty way to look at that by just applying the high school Physics law on gases, P1V1/T1 = P2V2/T2. It occurred to me that this could also (potentially) be helpful in trying to assess using published load data with a different bullet than what was used in the recipe.

So I spent an evening creating a spreadsheet to semi-automate that process, and I created a lookup table with case dimensions and volumes for several of the more common handgun cartridges. I wanted to use GRT to see if the results might validate (within the limits of the oversimplifications involved) my experiment.

I don't recall when I first looked at GRT. About a year ago, I think, and at that time it didn't have any powder I use or had easy access to, so I never used it again. For this experiment, I downloaded a fresh copy and found that GRT now includes data for both HP-38 and Winchester 231. That's my powder, so I went forward.

Rather than rely on my sketchy chrono records, I used as a basis for comparison an article from Shooting Times detailing the process of finding loads that make power factor for IDPA. I saved the article, both as a link and as a download, because it conveniently used Winchester 231 and the two Berry's .45 ACP bullets that constitute the bulk of my reloading. The article tested each bullet (a 230-grain RN and a 185-grain RN-HB) with three charge weights -- 5.3 grains, 5.7 grains, and 6.1 grains.

The discrepancies between the actual results and the GRT predictions ranged from 8% for the 230-gr bullet over 6.1 grains, to 37% for the 185-gr bullet over 5.3 grains. In general, the discrepancy for each charge weight was double (or more) for the lighter bullet than for the heavier.

So I don't feel comfortable using GRT -- not to try to validate my quick-and-dirty spreadsheet, or to evaluate handgun loads. If GRT were 10% conservative across the board, I could happily live with that. A 37% error is more than I'm prepared to deal with -- especially since the discrepancy is different for each load, so there's no way to know what the margin of error will be for the next load I enter.


Unclenick said:
His 7.06% vs your 7.59% is because you calculated the percent by which the prediction exceeded your measured value, while he calculated the percent by which the measured value was smaller than the prediction. In other words, you made 869 fps the 100% value, while he made the 935 fps the 100% value. You gave the prediction's error relative to your gun, while he gave your gun's error relative to the prediction.

Obviously, your approach makes more sense in this context because reality rather than a modeled estimate is what matters, in the end.
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Yes, I understood that immediately. Percentage of difference is calculated by dividing the amount of difference by the original value. If you use the larger value as the "original," the percentage of change will be smaller. And I obviously used the actual, real world numbers as the original when I computed the percentage of error. It doesn't make any sense to argue that the error in any theoretical simulation should be computed using the theoretical result as the original value, and the actual value as the variable.

But it makes the error look smaller, so why not use it? What was it Mark Twain said? "There are three kinds of lies: lies, damned lies ... and statistics." What good are numbers if we can't manipulate them to suit our purposes?
 
As any other simulation tools, I trust GRT always with a grain of salt. I always double check it with other sources, including my own calculations and gut feelings. So far it has been working out for me.

-TL

Sent from my SM-N960U using Tapatalk
 
I would not be satisfied with that response, either.
I think calling it "courteous" and "defensive" is very conservative, as well.

I'm not terribly surprised, though.
Last year, they sent an email out, asking people to vote in a survey to indicate what feature or data set needed the most attention from the developers.
I voted for the powder database and was prompted for a comment. I said something very simple, like "without more North American powders, the program is nearly useless to me." And I went on with my day.

But, the next day, I had an email in my inbox that I felt was a rather harsh and angry response that, to me, read like they felt they had been attacked by my comment - in a survey that they asked me to vote in(!).

It seems like they don't understand the difference between feedback and criticism.



And, I do agree. QuickLoad has plenty of limitations, as well.
For example: I still can't get it to make sensible predictions for .458 SOCOM and .475 Tremor, even with custom powder profiles. I can dial it in for one load, but it'll be way off for the next one.
And I've been waiting ... 4 years (?) ... for about half a dozen powders to be added to the database. Still no update.

Edit: I see that QL had an update issued on May 1st. Perhaps I'll finally get some of my powders.....?
 
AB I recently downloaded GRT based on you highlighting it in a thread. I haven’t shot for recreation or reloaded in a year due to deployment. I’ve been playing around with it, along with a friend in my platoon who also reloads. From the best I can tell, it is ballpark accurate for most of the loads that I recall making. Specifically my H4895 load in 7.5 Swiss. My friend also expresses that it provides velocity models that closely matches his experience. He hot rods and focuses on velocity much more than I do, often exceeding max SAAMI pressure in cases where it is logically safe (300 blk comes to mind). It also closely resembles published load data I can find. Since we all know even published loading manuals often have conflicting load data, GRT is just a tool in the tool box. I don’t expect it to be perfect. Admittedly, I haven’t worked up a new load that I’ve tested real world with any input from the program.

And 37% off is a whole bunch. It seems to be within 10% or so on my known loads. Just to check a possibility, you didn’t have the wrong barrel length inputted did you? I ask because I was getting a result that I knew was way off a couple of times... turns out 10 extra inches of barrel can do that.

As to the email, yeah that was a bit standoffish. Since this is a free program we don’t have much choice but to accept that, as offputting as it is. I like how the model can take inputs from users to try and refine it. I’m going to test some loads by it when I get home (staying within published loads or something I know for a fact is safe). I had thought about supporting the patreon channel. Now that I’ve seen that email though... I don’t know.
 
I still want to support them, albeit the unpleasant email. I'm using their work product for hobby. It is fair to pay $12 a year for it. Besides the tools is not bad.

-TL

Sent from my SM-N960U using Tapatalk
 
New question: I've been adding Berry's handgun bullets to their database. No problem with .45 Auto. BUT ...

When you go into the bullet database and click on "Add new" you get an entry for "Caliber diameter" and another for "Projectile diameter." So what would I put for "calibers" such as .380 ACP, .38 Super, .44 Special, and .44 Magnum?

Putting it another way, if you were looking for bullets for a .44 Special handgun load, would you look under .44 or under .4320 (the SAAMI max spec for the cartridge) or .429 (Berry's actual bullet diameter)?
 
Introduction to the Thread

My name is Charlie, and I am one of the GRT USA representatives. You will find my name in the GRT Development Team listing in the Help Files (F1).

I see there is some discussion on this thread about how well GRT simulates Interior Ballistics. Before I go into detail on any of the possible miss conceptions I have read on this thread, I think I should lay a little background for the readers.

GRT is a Interior Simulation that is being developed in Germany, by mostly, German as first language participants. As English is a second, or third, or fourth language to these people, it would be kind of us Americans to cut them a little slack, and not interpret their replies as arrogant. German thinkers naturally have a tendency to translate their thoughts into (the German term) Denglish. Then the American speaker needs to develop the ability to work out the real meaning of the sentences, and not assume someone is being rude. Try translating American word for word into German, and see what you come out with. It will not be pretty. For example, I always thought the term "Ja Ja' meant "Yes Yes", but in Berlin it means something like "Kiss my !@##".

Next thing to remember, is that the Reloading Community in the EU has many more regulations to adhere to than we in the USA. They have restrictions on the amount of components they are allow to possess at one time, and have to attend Reloading training classes. Therefore, a program like GRT is a necessary tool so the reloader can make proper selections of components for his firearms. Ii will continue later.
 
GRT in General

First let us try to understand that GRT is in Beta Development. That means it is to quote a Philippine term "not cooked yet". If it were a Commercial Release, buyers would have the right to complain. However, GRT provides a Trouble Ticket system on the www.grtools.de website where anyone can register for free to download the software. There is no requirement for credit information. The program is offered to the whole world at no cost. Also on this website, there are URLs available so the users can join the GRT Discord server and participate in various discussions pertaining to GRT and Reloading in general. This Discord server is being hosted in English in order to make it easier for English speakers to enjoy the tools, and forces the Europeans to communicate in a non native language. We Americans should appreciate the effort being expended to make GRT world friendly. Various international users are translating the German text into several languages as this is being written. This is being done voluntarily at no cost to any users because there are many people in the world that see the worth of the software. GRT does however, cost Gordon, who has undertaken this project for the betterment of the world reloading community. He is not trying to get rich in a Capitalistic way, he is trying to enrich the community and international relations in a way no government can.
 
So what is right, and what is wrong in GRT

First the user needs to understand that the databases within GRT are not complete (part of the Beta reason). Bullet files are provided from the best data GRT can acquire, but contains errors due to parameters being lacking from the sources. A good example of this is within this thread. A 185 grain Berry's bullet was placed into the users simulation. The bullet file was entered by the user, and marked as "Hollow Based", but the hollow base dimensions were not entered into the file. This creates a garbage file, and we all know that garbage in equals garbage out. That is one explanation for the mismatch between the users load data and the GRT simulation. Additionally the user had no idea of the source data parameters like fired case volume, case trimed length, and he entered a hollow base bullet as flat based. The flat base alone could cause a 37% error, typical GIGO. Additionally, the user failed to provide GRT with a copy of his .grtload file, so GRT had no way of comparing the users inputs to the real world. We at GRT would appreciate that negative comments be withheld by thread users who have admitted in their emails to GRT, that they really do not understand how to use the program works, but something must be wrong if my simulation result differs from published data is a magazine. You would be comparing apples to oranges, and that is not fair.
 
So what does GRT offer?

Unlike commercially available products, GRT provides database updates very often. Additionally, propellant models that are not currently included can be reverse engineered if enough users submit structured test data, and existing models will be improved by the submission of standard user submissions. The more we get the better the model will be. GRT also offers indirect contact with the developer (try getting that with paid for programs), and if you join the Discord server, you may even be able to make direct contact with Gordon. He monitors the threads, and will respond if he can. However, we must understand that he has a full time job, and does this project on his free time.

So come join us, read the Help files completely, and participate. Those reloaders who show the ability to supply meaningful data sometimes get invited into the inner workings. Enjoy a user friendly GUI, and the ability to store all your results in one file with the ability to import chrono data, store pictures etc., and for Pressure Trace users you can even overlay the PTII data on the GRT results graph. This takes propellant modeling to a new level.
 
Ewa Thoughts said:
First let us try to understand that GRT is in Beta Development. That means it is to quote a Philippine term "not cooked yet". If it were a Commercial Release, buyers would have the right to complain. However, GRT provides a Trouble Ticket system on the www.grtools.de website where anyone can register for free to download the software. There is no requirement for credit information. The program is offered to the whole world at no cost.
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I fully understand that GRT is in development. The web site asks for feedback, presumably as an aid in the development process. So I provided feedback. I had run a simulation, and I had actual published results, provided by a respected author in a respected publication, to show the the results in GRT were WAAAAY of the mark.

I did not ask for a response. I submitted the information in good faith, with the expectation that it would be used in good faith to help fine tune the program. Accordingly, I was more than a little surprised to receive the response that I quoted above. Not only did it come across as defensive, it selected for discussion the one result that was most favorable to GRT (by virtue of demonstrating the least error), and then on top of cherry picking the best result he further downplayed it by using the theoretical value as the base rather than the actual value, which has the effect of reducing the magnitude of the error from 7.6% 7.1%.

So come join us, read the Help files completely, and participate.
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I tried to participate, and as thanks I received what I consider to be a slap in the face. And don't lecture me about German. My grandfather spoke German before he spoke English.

The bullet file was entered by the user, and marked as "Hollow Based", but the hollow base dimensions were not entered into the file.
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The hollow base dimension were not entered because there is no way in the new entry screen of the bullet database (that I could see) to enter it. If it's there, it's VERY well concealed. There is a place to toggle the bullet base, and this was set to "hollowbase."
 
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