Getting QL to match a single load's range data is not a problem. All you need do is change the burning rate factor until your charge weight matches the MV that QL predicts and Bob's your uncle! The sticky bit comes when you try to use the predictions from a single set of QL variables to match the range data you developed from a variety of different charge weights. Then you have to resort to tweaking other parameters besides just the Ba.
These are notes left in another gun forum by a gent named Chris Long. Chris is the creator of the
"Optimum Barrel Time" (OBT) method of load development and, IMHO, probably knows the ins and outs of QL as well anybody apart its creator, Hartmut Broemel.
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I have been improving this process, and hope to be able to update that paper eventually. Currently, my three main "tweaks" in QL are:
1.) Burn rate - no more than 5% higher or lower. More than that and I go to #2
2.) Weighting factor - no more than 10% change from QL default, else go to #3
3.) Bullet weight - this is a very good way to compensate for bore friction and other physical things that QL can't model. An increase in friction effectively reduces the accelerating force on the bullet, slowing it down. Increasing the bullet mass does the same thing in QL (F=MA). If you have to tweak this by more than a few single digit percentages, then there is something very weird going on. If things get too weird, reset it all to QL defaults, and start over with just the bullet weight and see what you get. I had one Savage 6mm barrel on a friends rifle that was really rough, and required a 3 grain increase in bullet weight (from 105 grains) to get the velocities to match. It was the only tweak that would let the model even get close to the right predictions.
The process is trial-and-error, tweaking these parameters until you can match at least two velocity measurements. I usually fire at least three different charge weights, from low to high, trying to bracket the expected OBT velocity range(s), and record velocity for each trial. It is best to fire 5 shots at each weight, if you have the patience, as the velocity average will be much more accurate than a single shot value. Single shots are OK to get you in the ballpark, but to get a good QL model, you need more than 1 at each charge weight. Then, tweak QL until you get the best match to your data samples.
You will find that it is very difficult, if not impossible to get an exact match for some component combinations. I am convinced that there are non-linear effects in the actual powder burn process that QL's linear system models do not encompass. However, if you work at it, you should get the model to match well over the range of velocity that encompasses the OBT you are shooting for. If in doubt, try narrowing the test velocity range around the target OBT node, and try again. Once you get QL calibrated, you can adjust the charge weight in QL to hit an OBT on the nose. That will be your starting load for an OCW type test.
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I do know one other fellow who uses QL and OBT to quite good effect who tweaks the Shot Start (Initiation) Pressure. This makes sense to me because QL has no adjustment for either primer brisance or bullet jump, both of which definitely affect chamber pressure. Then again, it could be that Chris already has determined both those factors are well-compensated for by his bullet weight tweak.
This is part science, part voodoo. Some people never get the knack of it and arrive at the conclusion that QuickLoad either is inaccurate or worthless. I probably started out lucky because the way I tweak is as much instinctual as intellectual, yet I'm able to skip merrily from one accuracy node to another and accuracy/group size remains virtually identical.
I'm keen to add a Pressure Trace to my collection of tools, too, because you can correlate the data from a chrono, QL and the Pressure Trace to pinpoint a barrel's accuracy nodes with astonishing precision. It's on my "must have/must do" list, right after an Aston Martin Vantage, a weekend in the Elvis Suite in the Las Vegas Hilton
and a Barrett .50 cal.
will the RFD not replace it for you? Now that I really look at you'r initial question I see my answer didn't that much so I spent a little while looking around the web. Now, I can reload but internal balistics makes my head hurt but I found a couple of items that might help you, however you will have probably been doing a lot of seaching yourself so they may be of no use to you.
). One of its best features is the ability to "audition" different bullet components to predict their affect on performance.
