Quickload simulation help

[Klem]

I personally don't see a difference between case capacity when I measured several samples of Lapua, Hornady, and even PPU brass.

Everything was around 35gr H2O.

No way that 31.2gr load is doing even 50ksi. Quick Load needs to be calibrated to get usable info for 6.5 Grendel. We've often seen 10ksi more predictions from it that were simply out to lunch.

I disagree with your sentiment where QL is concerned. I use it constantly and find it is a valuable tool for work-up's and what-if's.

It's a computer program so GIGO applies. We have seen from this thread that slight differences in case capacity result in larger differences in peak pressure. When loading on the raggedy-edge of what the brass and chamber is capable of containing then it behooves the user to enter precise data. All cases being 'around 35gr' is simply not precise enough. If you enter this then you get GIGO. It follows then that if you get 'Garbage Out' you loose faith in the program.

Yes, it will never be absolutely precise but your sentiment is akin to 'throwing the baby out with the bath-water'.

[rwh]

I've never gotten a good result without fudging the quickload parameters. There are plenty of links available through the google on the interweb that talk about ways to tune quickload to match the results you get from measuring speed with a chrono. I'm not sure I get the point of a program where you go out and get real world results and then feed them in to a simulation to match reality. It would be great if quickload went the other way but so far I don't see that happening. It does better with 223 and 6BR than with grendel but it still isn't a replacement for getting a load from a loading manual, starting low, and working up.

The OP was interested in optimum barrel time which is a whole different topic with plenty of interesting work. The OBT papers are also great as long as you have some real world results to compare to the predicted values. I don't see OBT charts ever replacing running a ladder test to find good loads.

[Klem]

All programs and models have their origin in the real world. QL is a mathematical model of the real world. Models are by definition simplifications of reality. QL is a mathematical simplification of reality. All models have varying predictive utility and limitations. QL has its limitations but is not as useless with Grendel as some posters would like us to believe.

I use QL for this caliber and can work with the results.

QL includes barrel length as a variable.

[JASmith]

All programs and models have their origin in the real world. QL is a mathematical model of the real world. Models are by definition simplifications of reality. QL is a mathematical simplification of reality. All models have varying predictive utility and limitations. QL has its limitations but is not as useless with Grendel as some posters would like us to believe.

I use QL for this caliber and can work with the results.

QL includes barrel length as a variable.

QL gets the barrel time by integrating the velocity versus time curve until barrel exit. The velocity is obtained by integration the pressure versus time curve.

The problem is that QL overpredicts reality when CFE by A huge margin. The barrel time calculation is not likely close enough to be useable even if one chooses a false powder charge weight to get the correct velocity.

[LRRPF52]

I disagree with your sentiment where QL is concerned. I use it constantly and find it is a valuable tool for work-up's and what-if's.

It's a computer program so GIGO applies. We have seen from this thread that slight differences in case capacity result in larger differences in peak pressure. When loading on the raggedy-edge of what the brass and chamber is capable of containing then it behooves the user to enter precise data. All cases being 'around 35gr' is simply not precise enough. If you enter this then you get GIGO. It follows then that if you get 'Garbage Out' you loose faith in the program.

Yes, it will never be absolutely precise but your sentiment is akin to 'throwing the baby out with the bath-water'.

I'm not saying QL isn't valuable. I'm saying with 6.5 Grendel, it needs tuning.

I just measured some samples of PPU once fired, non-sized brass, as well a Lapua.

PPU 1x 36.0gr H2O
PPU 1x 36.2gr H2O

Lapua 1x 36.5gr H2O
Lapua 1x 36.5gr H2O

Yes, it would be better to take 10 random samples from a pile, but I need to get busy with some things, but when I did this several years ago, I remember them all being within a few 10ths of a grain of each other off the top of my head. It was in the 36gr region as well, not 35gr. I don't know if I recorded those notes before other than on the forum.

I don't have any Hornady brass that isn't sized that I can find. I went on a sizing binge a few weeks ago and processed all my Hornady brass.