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quick load and the 6.5X47Lapua Question

 
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  #1  
Old 03-30-2010, 01:19 PM
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quick load and the 6.5X47Lapua Question

140 grain Berger VLD
Re-loader 17 40.4 grains
28 inch Hart tight neck barrel .290
Pressure signs, slightly cratered primer strikes, at 40.7 grains I get a sticky bolt. Most cases are twice fired, about 800 rounds fired.

QL settings Iíve changed. H20 48.9, Case length 1.83, Cart Len 2.79, Start Pressure Friction proofed added 5K to 7393 for Jammed bullet

Listed velocity is 2940 actual velocity is 2825 by crono, but My drop tests tell me the crono is about right.

Shoots good groups, .5 MOA 200-400 yards, a little better than that 500 to 800 yards.

If I raise the bullet weight I have to go to 158 to get close to actual MV, but my BT is 1.278 which is right on the OBT for a 28 inch barrel and it stands to reason as it shoots well. However, QL shows be over 10K more pressure than is acceptable.

I can get the same results by going to .95 on the weighting factor. Iím trying to get quickload to accurately predict bullet weight and charges that get me on the OBT node for different bullet weights without all the trial and error Iíve gone thru finding this one with the 140s.

I assume if I was actually producing almost 76K PSI that I would be showing more pressure signs than Iím getting. My primers arenít even stamped flat. Iím using CCI 450s.

I welcome any comments, suggestions, etc.
Robbin
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Old 03-30-2010, 03:05 PM
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Re: quick load and the 6.5X47Lapua Question

I'm not understanding your start pressure. What is your start pressure entry? The number that shows in the entry box?

I used 10,830 which is a jammed bullet on top of the normal jacketed bullet start pressure. That combined with 2.79 COL, 1.83 case length, 140 Berger VLD, 40.4g RL17, 28" barrel, gives me 2,944 fps @ 71,513 psi. BT of 1.216ms. That's the same answer as yours within the accuracy I'd expect from QL as an engineering simulation.

I don't give a lot of credability to barrel time calculations in QL. Measured BT using pressure instrumentation would be a lot more meaningful. I've never see a good predicted vs measured BT study done on QL so I have no confidence the predicted BT is correct within the accuracy limits that might be required for it to be useful. What are those accuracy limits?

I don't think group size is a validation of BT predictions, there is just way too much going on in a real rifle that isn't modeled in QuickLOAD or included in the BT studies to expect it to predict accurate barrel times other than by coincidence.

Your MV results are within 5% which is all one ought to expect of a tool like QL. Trying to use it to predict barrel times within a couple of tenths of a millisecond is more than this tool will do reliably. The only way to know BT that accurately is to actually measure it using pressure instrumentation.

Fitch
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Old 03-30-2010, 03:55 PM
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Re: quick load and the 6.5X47Lapua Question

I added 5K to the 2383 start pressure which took it to 7383. I had read that people got better results adding 5K as opposed to adding 8K

You probably know a lot more about it than I do, but , I'm a Barrel Time believer. The rifles I've got that Quick load does produce very accurate velocities for, when the QL BT matches the OBT for harmonics, it's EXTREMELY CLOSE to the best load Iím going to get. I usually ladder up and down a grain at a time and nail it. In my experience, with 5 other rifles that do match QL velocities, the accuracy node suggested by barrel time has been correct.
Pure chance? Could be...

But my two favorite rifles are both 6.5X47Lapua and I canít get QL to even come close without really messing with the numbers.
Iíd like to find something that I trusted to jump to other bullet weights with. And I donít know if I start messing with the numbers like weight factor if I can then use other powders and bullet weights and get meaningful results.
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Old 03-30-2010, 07:17 PM
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Re: quick load and the 6.5X47Lapua Question

What case & H20 capacity & bore volume are you using?

I don't personally see any value in the cartridge. And I know it's numbers are never gonna be good. But QL can be calibrated to it. That I'm sure of.
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Old 03-30-2010, 08:43 PM
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Re: quick load and the 6.5X47Lapua Question

QL settings Iíve changed. H20 48.9, Case length 1.83, Cart Len 2.79, Start Pressure Friction proofed added 5K to 7393 for Jammed bullet

These are the settings I've changed, so the H2O capicty is 48.9
Case capacity was set by quick load to 42.3. The case and Cart len I set by actual measurements.

All other are set by QL I didn't see a bore volume but I did see a cross sectional bore area that QL sets to .53615

Oh, I am using the default friction proofed for Moly bullets.

Thanks,
Robbin
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  #6  
Old 03-30-2010, 10:51 PM
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Re: quick load and the 6.5X47Lapua Question

The default cross sectional bore area values are sloppy in QL. You'll notice it changing from one cartridge to others in cal. They should have picked a beginning standard here.
Big affect

Where did your H20 capacity value come from? Did you measure it?
Not saying it's wrong without lookin it over, just wondering..
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  #7  
Old 03-31-2010, 08:02 AM
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Re: quick load and the 6.5X47Lapua Question

Yes, that is a measured weight on the H20, I took 5 and averaged them.
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