QuickLOAD and Large Capacity Cases like .50 Alaskan, .50-90 Sharps, etc.

[gitano]

I've been using QuickLOAD for at least a decade I think, and am facile with its use. I have a need to develop some loads for .50 Alaskan, 50-90 Sharps, and .416x.348 Win. "All of a sudden", (with these large-capacity, straight-walled, and almost straight-walled cases), QuickLOAD is grossly underestimating MVs. Some by more than 200 f/s. Is there anyone here with experience using QL for large capacity, straight-walled, cases that has gotten it to make reasonably accurate predictions of MVs? Large-capacity, BOTTLE-NECKED cases, (say .300 Winchester Mag or .416 Ruger for example), don't seem to be a problem, but these large straight-walled cases are giving me fits.

TIA
Paul

 

[jepp2]

Paul,
I'm not going to try and take the time to find it in the manual, but what I recall reading from several years ago is that QL is basically designed to work with bottle necked cases, and the model works much less reliably with straight wall cases. This is why handgun loads should be approached with more caution.
Have you tried adjusting the powder burn rate (Ba) to get a better match? It is something I do all the time even on bottleneck cartridges when I am trying to improve my results. Especially when I am trying to find the load for a node in optimum barrel time.
I have found it to work acceptable for my needs even with straightwall handgun cartridges, but I start by assuming the calculation is much less accurate until I get some data.

 

[gitano]

jepp2 - Thank you for taking the time to reply. I'm not particularly comfortable with manipulating Ba when working up loads. When I'm close, and I can adjust Ba to get QL-predicted MVs to match actual MVs, I'm "OK" with that manipulation. Bromell's recommendations for adjusting Ba are to keep the adjustment to 15% or less. I can't get the MVs QL is predicting to get close to my measured MVs with even a full 15% reduction in Ba. Furthermore, I don't trust the resulting max pressure estimate by QL, and I pay particular attention to max pressure values. Finally, I also don't trust the resulting QL timing information, again on which I rely to get me relatively close to Optimal Barrel Timing theoretical nodes.

Here's a thread I started a while back that more thoroughly and clearly gives my point of view on changing the Ba variable in QL: http://forum.accurateshooter.com/th...k-densities-and-accurate-predictions.3881154/

Unfortunately, (for me), I think you're right about QL and bottle-neck cartridges. I've come to rely on QL to significantly reduce the time and resources required to work up a load, especially for wildcats. I am bummed that I am going to have to waste expensive and difficult-to-obtain bullets and cases because I can't get QL to 'work' for these types of cartridges.

I think I'm going to 'fiddle with' Accurate 5744, (which means revert to the "old" way of working up loads), and see if I can't get what I want (a 500-grain bullet doing at least 1650 f/s at a max pressure of less than 30kPSI), with that powder. From what I'm reading around the internet, "everyone" seems to 'like' 5477 in the .50-70 Gov't, .50 Alaskan, and 50-90 Sharps. (At least those that don't get 'the vapors' at the thought of using nitrocellulose powder in a "black powder cartridge/rifle".)

Paul