Thread: Quickload
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Old December 27, 2012, 10:23 AM   #2
Join Date: March 4, 2005
Location: Ohio
Posts: 14,067
It's not considered rude, but folks who like the program want to encourage sales to support the author's further work on it. He has to keep testing powders for updates. I would say you should feel OK to make a few such requests, but then buy the program for yourself. For one thing, it's multitude of adjustable arguments is an education in the factors affecting interior ballistics. For another, it takes somewhat more time and effort than you may be aware of to get really precise results, so you really want to be able to put that time in and not expect others to do a lot of it for you.

The main additional factors are, for any round peaking at over 30,000 psi, you need to enter the water overflow capacity of the cases as fired in your particular chamber. To find this you take a fired case that has not yet been decapped or resized. Measure it's length and jot that down. Weigh it. Jot that down. Then fill it with water just level with the case mouth but with no meniscus and no bubbles inside (tap it to dislodge these when it is nearly full) and no water drops on the outside. Weigh it again. Subtract the first weight from the second weight to get water overflow capacity in grains of water weight. That's the unit entered into the program. Report the case length and that capacity for use in the calculation.

You can also further refine the information with a chronograph to give you actual velocity. Actual velocities can vary 100 fps or more from predicted velocities because the QuickLOAD mathematical "gun" is more ideal than your actual gun is. Without adjusting for slugged bore dimensions, bore friction, and making allowances for primer and bullet hardness differences and other factors, it's pretty common for the program to predict velocity a bit on the high side. I'd suppose 50 fps high is pretty average, but I've had it be just about dead on in some instances, and high by as much as 250 fps in one instance. Occasionally you run into a gun with a "fast" barrel that shoots to higher velocity than is predicted, though that is less common.

The main thing, though, is that powders sold for hand loading have burn rates and energy content that vary ±3% from most makers, and also some variation in bulk density, which affects burn rate further in some powders. The program is based on tests from one sample which could be anywhere in the range. So you need velocity reading feedback to adjust the powder model burn rate and energy content to get more exact pressure and barrel time information (assuming you want that).

Where the program shines, though, is in helping choose powders and in revealing how much difference a change in charge will produce from an established load. The two exterior ballistics programs that come with it, especially the 3 DOF QuickTARGET Unlimited are very good.

In you particular case, the program defaults give me 46,692 psi and 2866 fps. However, my own AR's cases come out larger than the program's default case water overflow capacity, and if your chamber matched mine, I'd expect more like 41,000 psi and 2750 fps. So that factor matters a good deal. Mixed cases in .223/5.56 NATO don't matter much as there is a lot less variation in case capacity in this chambering than there is, for example, in .308/7.62 NATO.
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Last edited by Unclenick; December 27, 2012 at 10:32 AM.
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