Chron results vs. QL "suggestions"

[deadwooddick]

Which to believe if QL says 3985 fps and the chrono (Oehler 35P) records 3645 fps ?

 

[Jay Christopherson]

You always believe your chronograph - QL gives you an idea of what to expect and in my experience, generally over-estimates the initial burn rate of the powder you are using. Once you start getting chrono numbers, you start modifying QL to match it up with the real-world results. After that, it should match up within a few fps or so (at worst) at any given charge.

 

[Ackman]

QL isn't there, the chronograph is. Why would you believe QL instead of the chronograph?

 

[watercam]

Reason being there are so many variables from barrel length, rifling type, chamber dimensions, brass used, primer used, variance in powder burn rate between lots, etc. etc.. Factor in which ever you can and analyze from there.

 

[normmatzen]

I depended on electronic circuit simulation for most of my career and the 10 years since retiring. As an old analog designer, I did a lot of designs before the computer raised its ugly head, I learned to ALWAYS take simulation results with a grain of salt and use them primarily to determine trends.
Same as QL, you can see what a change in any parameter will do, but can't expect exact results. I do shoot some cartridges that come out VERY close like my 6BRX, but my 7X57 with RL-17 doesn't give me the best of results. My 284 WIN heavy gun is pretty close too, which makes me think Hodgden powders have more realistic data files than some of the less popular powders.

Some times I fiddle with some of the parameters to get more realistic numbers, but often the changes are not linear with parameter changes. I don't understand powders and burning functions so I drop back to trend determination and am a happy user.