Reference material disparities

B

Brutus

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Ok so it use to be I was only puzzled by varying data found in different reloading manuals but no I had to go and get a copy of Quick Load to help add to my bewilderment. Case in point.
Sometime back I was toying with defense loads for my 10mm. Had some AA#9 on hand and at the time only the Hornady 5th. edition manual offered any data for that powder.
Test pistol Colt Delta Elite 5" barrel, 1 in 16 twist.
Bullet 180gr. XTP HP.
Min. 11.5gr. AA#9 for 950fps. 1.260 o/l
Max. 14.4gr. AA#9 for 1200fps.
After working up the ladder I chose 13.8gr. for 1150fps. as a final loading.
I have since added a Modern Reloading manual and they list.
Min. 12.2 for 1093fps.
Max.13.5 for 1242fps.

Actual Chrno. readings for a 5" 1 and 16 Kimber
13.8 gr. AA#9 Min. 1227fps. Max. 1266fps. Avg 1248fps.
Chrno. results from a new precision electronics matched old readings from my shooting chrony.
Quick load reports with all matching parameters.
1487fps with 74139 psi. and a big warning " Do not use this load".

Actual results don't support Quick loads output but none of the reference materials hit the nail on the head. What am I missing on the quick load parameter settings?:confused:
By the way all of my target round data have been very close to Quick load predictions.
 
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Interesting, I tested a similar load this weekend out of a Glock 20 with KKM barrel and 24 lbs RSA. Powder was newly purchased and I went off the Accurate website as Hornady #9 had much higher charges. Accurate website said 13.5 grains was max load.

AA #9 13.5 gr - Hornady 180 gr HAP - Federal 150M - OAL 1.250

Hi Vel: 1307
Low Vel: 1288
Ave Vel: 1298
Ext Spread: 19
Std Dev: 6
 
Is the Hap bullet the same dimensionally as an XTP?
Is the barrel polygonal?
What barrel length and twist?
My next step is to take a mold of my actual barrel dimensions and measure the H20 capacity of the cases. Something has to be corrupting my data.
 
I believe Hornady claims they are XTPs, but without the folds and cannelures, so no expansion. KKM barrel is normal rifling and standard drop in length (4.6" I believe). I have no clue on the twist, I'll email them.
 
My impression from a number of Quickloads reports I've seen floating around over the years was that they may rely in many cases on limited experimental data to develop a 'model'. I could be totally wrong on the approach taken, it's just sort of a gut feel I've gotten.

Suppose for example you have 3 data points spanning 10.0 gr to 11.5 gr of propellant for a given bullet, and you assume an exponential curve fit. Between those charges, you're likely going to do okay. But if that's your 'model', fit a curve to the data, you're going to be sucking gas real quick anywhere outside that range of loads. You may not do all that well within that range, either, but outside that range, forget about it.

I have no idea how Quickloads was developed--it's just been my impression, based in part on results like yours and in part on the price of the product, that it's really more of a 'fit a curve to sample data' kind of tool, rather than an actual interior ballistics modeling tool. I would expect the latter would be a nearly-impossible task, but I might also expect a little bit better agreement with published data than what you're seeing. OTOH, trying to use published load data such as Hornady's to build a model would also end up an exercise in futility--none of the published muzzle velocities are probably closer than 10% to actual, and there are no pressures to work with. There's really nothing you can do with that data except fit a curve to it, and you can fit a curve to anything--doesn't make it a model.

What might make Quickloads more useful would be some boundary conditions for the use of a given load--upper and lower charges outside of which QL doesn't expect to provide useful predictions. If it doesn't have that already, it might be a handy thing to have.
 
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