I own QL and generally use it to compare velocity / pressure with a given load. How reliable is the pressure data ? I find that the powder charges are not real close, but in the ballpark and don't agree with the loading manuals.
Thanks,
Jim

Without access to a real ballistic lab with pressure measuring equipment, you'll never really know.

Personally, I stop if I reach published velocity with the bullet/powder combination in question, or reach the maximum powder charge, whichever occurs first.

norske:
That's what I do, too.

IMO, a chronograph is a better investment than QL.
Smitty of the North

To make my question clearer, if I take my chronograph numbers and compute with the powder, brass, and bullet into QL, then Ql will give me the pressure. Will this pressure figure be close?
Thanks,
Jim

I would say that it might be close but you can't depend on it.

In the absence of pressure testing, all you would have to go by is the velocity, which certainly has a realationship to pressure, not just peak pressure, but how long the pressure takes to peak, and drop. You will find the pressure curve, shown as a graph in the QL software program.

You would need to consult Loading Manuals to see what the top velocities are for that cartridge. You don't need QL for that.
Smitty of the North

You should be able to find some posts about QL and pressure over on the "Ask the Gunwriters" forum, where this matter used to be discussed.

Smitty of the North

FWIW, I wish I could fin the article and quote it exactly but this should give you the gist. The writer, writing about QL, said: (paraphrasing) "for those that dismiss such software's ability to accurately predict, or compile usable data, you should understand there's a reason NASA can rely on computer models to lauch rockets rather than launch a 100 test rockets for the "exact data" under real conditions...this stuff works."

IOW, it's not 100% absolutely accurate 100% of the time and I don't think anyone is saying it is, certainly I'm not, but it's a helluva lot better than many want to give it credit for being. It is a valuable tool, but it's not the only tool you should rely on.

I've often scratched my head over this loading philosophy. If you reach max velocity, before you reach max book powder charge then your at max...but if you reach max book powder charge 200fps short of max velocity, your at max? That doesn't jive if you think about it.

To me velocity is the single best key to predicting pressure without usuing something like QL or actual pressure testing equipment. A chronograph without QL is still very valuable, because you have some book data by which to compare. IMO, QL, without the benefit of a chronograph, would be almost useless...together they are 2 great tools, each enhancing the other.

I consider QL well worth its salt without parallel use of a chronograph, just as a chronograph is useful in its own right with no QL in the county. Best of all, of course, is the use of both in careful coordination.

An easily over-looked feature of QL � the "weighting factor" (in the lower right corner of the upper left window) � is IMHO one of the software's best assets. It allows you to "fit" QL to your gun so that its predictions for that rifle and cartridge are as accurate as you can expect.

� Chronograph your load with ten or more carefully loaded rounds.
� Enter all details of gun and load in QL � precisely. Enter the measured gross capacity of your cases and the measured OAL of the loaded round. Do not substitute "similar" bullets without entering their accurately measured dimensions. Pay careful attention to the dimensions of your bullets' boat tails.
� Adjust QL's "weighting factor" until QL's predicted velocity most closely matches your chronograph's average velocity for that load.
� QL's pressure predictions will then be as accurate for your rifle as you're likely to determine by any other means.

QL's predictions for other loads in that rifle and cartridge should be very closely related to reality. QL's predicted pressures, for example, are likely to be about right � at least as high as the pressures that your loads actually develop in that cartridge, in that rifle, possibly a bit higher � but a fair guess, in any case.

Like any other software, QL will give you garbage for garbage, good data for good data. It's as good or as bad as you let it be.

For example:
If your load chronographs faster than QL's estimated velocity (not uncommon if you're using "hot" primers), assume that the peak pressure of that load is correspondingly higher than QL predicts.

Ok, Dr H, this was a feature I wasn't aware of! A pitfall of "mooching" off of other's software! I'm now convinced I will need QL as quickly as I can afford it!

If you can manage it, Jim, don't wait until you can afford it.

It'll soon pay for itself, and you'll learn more about interior ballistics than you can imagine. And you'll enjoy the experience.

Where else can you get all that for just $150?

As you use QL and get to know and understand what it can do for you, you'll see clearly that those who speak ill of it flat don't know how to use it right.

I wholeheartedly believe in it's utility and accuracy. I've carefully studied some data on the .280 that I've been provided, matching it to book data and listed pressures, and the velocities I get with my loads in my guns. All match up very closely when you factor in any differences in such details as bbl legnth from one data to another, etc. Being able to personalize it to your gun and your components, that gets down to serious detail, and that makes it a downright need for any serious reloader.

Those internal ballistic curves we've all seen are "best fit" diagrams.
I want to avoid any unusually high pressure sample point.
These can occur if either the powder charge is greater than that published by a real ballistic lab, or if you(like me)reduce the freebore for accuracy's sake, and reach published velocity early.

I wish I knew exactly what you meant by that.

Dr. Howell's point is well taken - the program seems complicated at initial usage and the appearance of complexity will discourage all but the most dedicated. In fact, if one studies the algorithm's variables in detail, it becomes obvious that most aspects of input are not only available but can be tweaked to a minute degree of accuracy. All of these input entries showing up on the very innovative GUI can be a bit intimidating in the beginning...I assure everyone interested that they are not once you get used to having them in front of you and if you put the proper amount of time into referencing them.

Using the lesser software on the market is expedient and less expensive but leads one into believing that the program is doing something for you that it is not. There is no substitute for knowing what you are doing and a computer program is not magic...QL is just substituting computer power to replace your hand calculations and a most complete data base of components and variables one can apply to those calculations, to which you can add data at will. It also puts all this power into a one page display...no more piles of books and papers surrounding the reloading bench. Of course, the algorithm itself is superior to predecessors but that's why you're paying the premium price for the product.

I believe that having all these variables available can teach the user a lot about reloading that he must dig through countless volumes of reference to find. That in itself is worth the investment. Being able to tweak such variables ad infinitum gets you more than your money's worth.

I am now an official QL novice...and am learning a lot with it. But, then I like that sort of thing.

One element in the output I found interesting is regarding the percentage of powder burned in a round. I have been thinking all this time that a certain powder was dirty when others were bragging on how clean it burned. As it turns out, the powder is not 100% burned in my cartridge with my barrel length, etc. Now I know. So, I can either change to a powder that is more efficient or just live with it. But, I can't blame the powder for being dirty any longer.

Great point, Steve, and exactly exemplifies what I am attempting to convey...you get more than your money's worth with QL. I am constantly finding more value in my daily use.

Great points! That I understanded!