How accurately can we predict the results of a wildcat?

[jonsidneyb]

How accurately can we predict the results of a wildcat?

Lets say we take a known cartridge and move the shoulder back 2mm. Or if we change the neck length.

If we make changes to a known cartridge can we get a fair idea of what we will end up with?

Are there guides to help us make a educated guess?

 

[robbor]

I believe there is a PO ackley book on designing cartridges. Also I have heard of reloading programs that will estimate on a designed cart, not sure of which program, I want to say Xball or something.
Basically Id just go by the closest case and capacity. The shoulder has to do with efficiency and brass stretch, and the neck is normall based on whats left although many believ a longer neck like .333+ will extend the throat life slightly.

 

[Forum Boss]

If you can figure out the likely true case capacity of the round, and it's not super-radical,Like something with an hemispherical shoulder), QuickLOAD can predict the pressures.

Normally, I can get QuickLOAD within 50 fps of the actual results for most any cartridge. However, some of the powders in the QL database just don't simulate well--a case of poor or outdated propellant info being provided to QL's designer.

You also need to double-check the bullet diams. and measurements. Sometimes these are off. If you're seating in the lands, set the start pressure to 5000-6000 psi instead of the default 3626.

 

[ConnorExum]

If you can figure out the likely true case capacity of the round, and it's not super-radical,Like something with an hemispherical shoulder), QuickLOAD can predict the pressures.

Normally, I can get QuickLOAD within 50 fps of the actual results for most any cartridge. However, some of the powders in the QL database just don't simulate well--a case of poor or outdated propellant info being provided to QL's designer.

You also need to double-check the bullet diams. and measurements. Sometimes these are off. If you're seating in the lands, set the start pressure to 5000-6000 psi instead of the default 3626.

But there is more than just that you need to know entire host of conditions to really predict performance. For example the pressure is important what about the optimal bore volume for a given pressure developed over a period of time given a specific velocity of gases. I mean you have 10,000 psi in gas pressure but have very slow gas velocity and that will effect the overall velocity of the bullet.

 

[mikecr]

Far as I know, QuickLoad is the only thing that will predict internal ballistics. It's the only thing that can be calibrated to your barrel.
You can use the 'cartridge design' feature within RCBS Load to determine cartridge dimensions & H20 capacity. QuickDesign can do it, but nowhere near as well.