If you decide to try GRT, there are a few YouTube videos I suggest watching. And since you are a QL user, you will find it easy to learn. I use both, but always confirm with loading manuals as to max powders before I attempt, and find max in my rifles.
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MagnumManiac
Well-Known Member
Personally, I found QL to be useful determining start loads and suitable powder for wildcatting, but it fell well short of reallity with the actual charges pressure.
I bought a Pressure Trace after QL, not once did it ever match the raw data that the Pressure Trace showed…even with parameter tweaking it was far off actual results…I sold it after many months of trying actual results to match QL.
Now, for regular cartridges, just use book data.
Cheers.
I bought a Pressure Trace after QL, not once did it ever match the raw data that the Pressure Trace showed…even with parameter tweaking it was far off actual results…I sold it after many months of trying actual results to match QL.
Now, for regular cartridges, just use book data.
Cheers.
Very interesting. Since you do have pressure trace, have you attempted this with GRT? I would be curious to see how it fairs.
TIA
MagnumManiac
Well-Known Member
No, I have not ventured into those realms again. Pressure Trace gave me my desired results…raw data straight from the rifle and load used. Best thing is there are no fudge factors involved. No calibration either, although many desire this option, I don't see any benefit because no company supplies raw data with their ammo.
Cheers.
Thank you sir!
I don't know much of anything about Pressure Trace, but in theory it seems like a great tool.
What can you share about it and when you say it didnt match QL parameters- was there any consistency to it or was it all over the board?
MagnumManiac
Well-Known Member
Pressure Trace is a very forgiving piece of equipment. Early on, I would mount the piezoelectric on a surface of the barrel that equated to 1/3 up from the base of the case, this worked on most rifles without a hitch. The only times it didn't was if the knoxform was very short and heavily tapered, this gives less than ideal results.
Cartridges like the 17, 222 and 223 based cases proved difficult to measure accurately, but I endeavoured to get results I could use.
Now, going back to QL, no time or cartridge did the pressure values match my results. I had velocity readings from the outcome, but never did QL match the pressure I obtained, very heavy tweaking changing powder heat and other factors were involved to come relatively close.
It was totally predictable to not match my pressure results. In fact, when I started my 416 Rigby based wildcats, I had 2 brands of brass to work with that had very different capacities, QL asks for H2O weight capacity, I don't like that for one, now the predictions made with the same powder, H50BMG, was 12 grains difference between cases. Over the Pressure trace, the heavier case with LESS capacity over pressured well before predicted, and the much lighter case with HIGH capacity never reached max with predicted loads from QL. Now, this may have happened without QL, as there is no tested data to compare to, but normal load testing would have gotten me closer than this using the Pressure Trace alone. I must say, I did not have the pressure trace at that time to test with, solely QL which predicted wrong anyway. I also wasn't HBN coating bullets at that time either, but you see how QL wasn't happening, it only got me in the ballpark.
Anyway, I only found it useful finding a powder and start loads for my wildcats, it was practically useless with normal cases because it rarely matched the book numbers.
Cheers.
There are several input parameters in QL that allow you to adjust initial pressure and few other parameters.
Seems to me, that pressure is closely correlated to velocity, a proxy for velocity if you will.
With velocity, I never match exactly predicted vs. actual muzzle velocity initially.
What I do is history match my actuals by varying the powder burn rate until I history match actual chrono velocity w predicted.
I believe that the right way to use any model, whether its GRT, QL, or a physics model of rocket trajectory to Mars is that it has to be tuned and tweaked to history match actual data.
So, in the case of pressure, I would suggest varying the input for initial start pressure and Ba, burn rate until the model matches the actual observed and measured trace pressure.
Not, only that, but because in a way, your rifle system is actually a proxy for a PVT bomb but with a hole in one end, I would vary initial pressure, and Ba and possibly a few other knobs or variables until I could history match both the observed pressure trace and the muzzle velocity from chrono.
Then, my man, you have a model. Then and then only.
You can't buy any model off the shelf that without tuning and tweaking will give exact actuals using a set of assumed best guess inputs to start with.
Doesnt exist.
