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Creating A New Cartridge Using QuickLOAD
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Old 11-22-2016, 01:49 PM
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Default Creating A New Cartridge Using QuickLOAD

This is probably going to get a bit 'esoteric'. (Esoteric - intended for, or appreciated by, a small number of people with a specialized interest.) I can tell by looking at THL's daily statistics that there are a considerable number of 'lurkers' that visit THL. I can only guess as to their interests, but more often than not, I see them looking for 1) info on makes of rifles like Parker Hale, or 2) info on loads for "esoteric" cartridges/rifles. I'm about to engage in a paper-whipping exercise to examine a QuickLOAD (QL) feature that allows one to "create" new cartridge/rifles based on specific input criteria. I know this ain't "reality", but I do find it interesting. (Recall the definition of esoteric.) You've been warned, so don't give me any guff about how "useful" this exercise might be in comparison to "pulling the trigger". Read further in this post with that in mind.

You give QL certain input parameters, and it 'turns the crank' to come up with case capacities and barrel lengths that satisfy that input. I've been fiddling with the 8mm-08, trying to find something I "like", and decided to 'freewheel' a bit instead of forcing my 'will' on the system. In this case, "forcing my will" means that I have a given cartridge, (8mm-08), a given barrel length (23.4375"), a given bullet (130 HP), that I am trying to find a good load for. "Freewheeling" means I will only specify the bullet, the MV, and the max pressure constraints. QL will calculate various combinations of case capacity and barrel lengths that will produce the MV at no more than the max pressure, using that bullet.

Since a picture is worth a thousand words, especially for y-chromosomes, I'll post some pictures to give the general layout. Then I'll go to my specific interests.



In the image at the "A" arrow is the primary tool for determining a charge. Clicking on that button opens the dialog box you see with arrows "D", "E", and "F". It is in that dialog box that one can set the criteria one wants to use to select a charge. QL uses data in the "Cartridge Dimension" page (partially hidden by the dialog box) to select charges. In this case, you can see the bullet I have chosen at arrow "B". The cartridge is at arrow "C", but since we are 'creating' a cartridge, that input value is ignored.

Within the dialog box, you can see at arrow "D" the Burn Rate window. You can see that I have set the sliders to "minimum" and "maximum" values, meaning that I want QL to consider ALL powders within its library of powders.

At arrow "E", you can see that I have set the max pressure value at 52,667 PSI. (This happens to be 87.5% of the 60,191 PSI which is the SAAMI max for the .308 Win. 52,000-ish PSI is just a good, reasonable place to set the limit.)

At arrow "F", you can see that I have set the "Minimum Load Ratio" at 50%. I don't want to consider loads that are less than 50% of case capacity.

One of the input criteria that is not in the image is the charge that I want QL to use for this new cartridge. I chose 50.0 grains. No particular reason other than it's a good 'round' number for a .308-sized cartridge.

Everything will be clearer in the "output" image.

Clicking on the "Apply & Exit" button in the lower right corner of the dialog box, the following list is generated:





You can read the column headers, but let me go through them anyway:
1) Powder Name - Self explanatory
2) % Fill Ratio - The percentage of the available case capacity that a charge of 50 grains would take up
3) Charge - In grains (Input criteria so they are all 50.0)
4) Charge - In grams (I deleted this column when I imported the data into Excel to sort and filter.)
5) Muzzle Velocity - f/s (Input criteria, so they are all 3000.)
6) Propellant Burnt - % of the charge that burns in the barrel before the bullet exits the muzzle.)
7) P Max - Max chamber pressure in PSI
8) P Muzz - pressure at the muzzle when the bullet exits
9) Case Cap. Grains of H2O - This is one of the output results that I am looking at.
10) Barrel Length - Inches. This is the other output result that I am interested in.
11) Barrel Timing - msec. I am interested in this, but not too concerned about it at this time because the charge is fixed. One can move the exit time of the bullet with changes in charge.

That's a LONG list, which if I counted right, has a least 200 rows. However, there are load density values that are ridiculous. A charge of 50 grains (the column to the right) of that first powder: Norma MRP 2, would fill the case (see capacity of this new wildcat cartridge in column 9 - 41.6 grains of water) to 146.2 % of its capacity. That's silly.

Additionally, I'm not interested in cases that have capacities larger than about 60 grains of water. Also, I'm not interested in barrels that are longer than about 28". Finally, I don't want to clutter the list with foreign powders that I can't get my hands on. So, I import this data set into Excel and start sorting and filtering out those rows that contain results outside what I am interested in. After performing that sort/filter, the list is narrowed to this:

The table is sorted on barrel length.

So...

If I want a cartridge that shoots my 130-grain HP bullet at 3000 f/s from a case with a capacity between 50 and 60 grains, while keeping the max pressure below 53,000 PSI, and has a barrel somewhere between 18.5 and 24 inches, these are the powders I have to choose from.

Let's look at some specific examples. Since I "like" powders to burn up in the barrel, I look for powders that have "100" in column "E" - % Burn. There is only one. It's at the bottom, which means it has the shortest barrel. Hmm... Longer barrels don't necessarily mean more burn because of the burn rate. The powder for this wildcat is Alliant AR Comp, and the barrel is only 18.5" long. The case capacity is nearly 60 though. I'd need to start with an '06 case and push the shoulder back to reduce the capacity so that 50 grains of AR Comp was about 102% of capacity with the 130-grain bullet seated 0.216" into the case.

Let's go the other way - 'long' barrel. Up at the top of the list with a barrel length of 23.1", we find Hodgdon CFE 223. Case capacity is 'nice' at 50.6 - easy to get from a .308 Win case. Burn rate is "poor" at only 92%, and Load Density is 'high' at 105.4%. (That'd work, but I wouldn't want to go much higher.) Barrel timing (1.001 msec) is within 2% of a timing node so that shouldn't need to be 'fiddled' with too much to find a timing sweet-spot.

So... You can see how this feature can be used. There are input values that can be changed to get different outputs. An important one is the seating depth of the bullet. Whatever you set it at on the "Cartridge Dimensions" page is what the calculation will be based upon. Also, as you have seen, the charge is fixed. I could change results by changing the charge to 50.1 grains. However, by performing this preliminary exercise and looking at the results, I can decide which direction I want to move both the seating depth and the fixed charge. You can't put a bunch of numbers in, turn the crank, and get a set of specs from which you can build a cartridge/rifle combination. However, you CAN put some specific numbers in, turn the crank, and get an idea about what NOT to do, AND an idea about the general vicinity of where you need to go.

Paul
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