Heat of Explosion/Potential in kj/kg for H1000?? (Quick Load)

harry_x1

harry_x1

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Minuteman
Aug 13, 2019
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#1
Hi All,

Trying to model the performance of my 33xc (30 inch 9t, 300 OTM, Catridge Lenght 4.332, 111.5 gr H1000). Predicted MV 2941 fps, actual 3064 fps.
Case H20 139 gr.
Cross sectional bore area 0.88691 sq inches.

The only thing IMO that can cause this variation in prediction and actual performance is Heat of Explosion. QL us using 3630 kj/kg. Are there any other folks who are using QL and can confirm what powder "Heat of Explosion" number they are using for H1000 and are getting accurate results?

Any suggestions on how I can get this QL to match reality, will help.



Harjeet
 
#3
I don’t touch that parameter. Instead I tweak the powder burn rate to more closely match the average velocities I’m getting. Also check your case volume on big magnums (H20 Capacity).*

*take a fired case with primer, place on quality scale, note empty weight, use an eye dropper with water/alcohol mix to fill it to top without bulbing (surface tension), note weight. Subtract first from second to get H2O Capacity
 
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#6
Doesn’t water and alcohol have a different specific gravity? What would the ratio be to be correct?

Sorry, I’ve never measure my capacity and am curious about it. If you use straight water does it hydrogen bond and create a bubble on top of the water?
 
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#7
When I first started measuring case capacity, I struggled to avoid a surface tension bulb at the top. Maybe I just suck at this? It was recommended to add a bit of alcohol and that did help prevent it. Not sure about the chemistry but they're both incompressible fluids, right?
 
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#9
A surfactant (dish soaps) will reduce surface tension. You can end up with a concave surface also not ideal. However, if you are consistent in the application, meaning you always have a dome or you always have a divot or you always have a perfectly flat surface, you will have a consistent measure to compare. 10 people will have 6 different results using the exact same gear.

Pure, distilled water has SG=1

Isopropyl will have SG of about 0.78 depending on the mixture. The impossibility of duplicating a mixture is why you should use pure, distilled water.
 
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#11
harry_x1 said:
I get H20 around 139.5 grains...which is close to the one that David Tubb also reports in his write up on 33xc.
Click to expand...
On Second thoughts, I was measuring H2O in once fired brass, but the Velocities I measured was in brand new brass. I am pretty sure the brand new virgin brass has slightly less H2) capacity. That would explain some of this excess velocity. Rest can be bridged by adjusting the burn rate factor.
 
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#12
100 ft./s out of 3000 is within 3% of the actual velocity.

Quickload is a modeling tool that has tons of inputs and probably at least half of them are assumed rather than specific to your actual application.

If you play with the starting pressure, it changes everything. If you change the wing factor, it changes everything. Your powder humidity can change everything (including it’s burn rate.) The friction experienced by your actual application, and your bore diameter, can change the observed velocities. Barrel breakin and cleaning can change velocity. Distance to lands (starting pressure.) etc etc etc

I’ve been using Quickload for 14 years and it only is within 20 ft./s or so of my actual velocities the minority of the time. With the cheytac and 50 BMG and larger cartridges, it is usually predicting 100 ft./s too low just like you were seeing. I use it mainly as a tool to get a starting point for unpublished recipes, and to get an idea of relative changes e.g. what if I increase my barrel length 5 inches or approximately how many feet per second can I expect to change for each grain of powder? for those things, it will get you in the ballpark, but observation on the ground beats predictive analytics every time
 
#13
secondofangle2 said:
I use it mainly as a tool to get a starting point for unpublished recipes, and to get an idea of relative changes e.g. what if I increase my barrel length 5 inches or approximately how many feet per second can I expect to change for each grain of powder? for those things, it will get you in the ballpark, but observation on the ground beats predictive analytics every time
Click to expand...

^^^^ this is how you get the most out of QL.
 
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