D
Deleted member 46119
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I've used this parameter to adjust for cartridge over bore or not but..
Anyone know of a formula for this?
Anyone know of a formula for this?
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Engineering101
Well-Known Member
jfseaman
Ah yes, the mysterious WF. I don't think there is a formula. After several years of using QL, I think I am finally using WF properly which is to say I change it liberally to get the results to agree with measured or published data - especially where the pressure is known.
I used to think that WF was fixed for a given cartridge but it isn't. If you think about it, it makes sense that it changes even by adding a few grains of powder as it represents the amount of powder sent out of the case to burn in the bore.
Ah yes, the mysterious WF. I don't think there is a formula. After several years of using QL, I think I am finally using WF properly which is to say I change it liberally to get the results to agree with measured or published data - especially where the pressure is known.
I used to think that WF was fixed for a given cartridge but it isn't. If you think about it, it makes sense that it changes even by adding a few grains of powder as it represents the amount of powder sent out of the case to burn in the bore.
D
Deleted member 46119
Guest
There is a spreadsheet of Weighting factors here: http://www.mamba-reloading.co.za/QL Weighting Factor.xls
Using the data from this source and the formula for the "over bore" index from http://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/
I tried to find a correlation.
I think I got it. It's odd but it is very close or exact for Pierre van der Walt's numbers.
Basically Magic number/Overbore Index.
For bottle neck cases the magic number is 500.
Example 223 Remington: van derWalt publishes .69, my formula is 500/773.9 = 0.65 for Weighting Factor.
Is this "perfect" no. Do the numbers make my real vs. QuickLoad closer, oh yeah.
Using the data from this source and the formula for the "over bore" index from http://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/
I tried to find a correlation.
I think I got it. It's odd but it is very close or exact for Pierre van der Walt's numbers.
Basically Magic number/Overbore Index.
For bottle neck cases the magic number is 500.
Example 223 Remington: van derWalt publishes .69, my formula is 500/773.9 = 0.65 for Weighting Factor.
Is this "perfect" no. Do the numbers make my real vs. QuickLoad closer, oh yeah.
jimbires
Well-Known Member
tag
Last edited:
wouldn't slower powders send more unburnt powder into bore? how about different shoulder angles? when I got quickload I tried to figure out what the things you could change without going into the program. for me the weighting factor has been trial and error using all the pressure signs to make sense of the outputs.
D
Deleted member 46119
Guest
Yes indeed. That has been a "challenge" for many QL users since forever.
I only took von der Walt's work and extrapolated into a formula that MAY be useful to QL users. Using van der Walt's numbers I got much closer to the expected velocities and pressures as checked against a Magneto Speed and Pressure Trace II.
Optimal Barrel Time predictions vs. real accuracy are also much closer.
Example: I just redid my 260 Remington load for 147 ELD-Ms. Without ever firing a shot, I was dead on velocity, no pressure trace this time but the "signs" match the QL chart. Barrel time was not actually measured since the Pressure Trace II was not used, however. I made a batch of ammo with one charge weight. Shot it. Accuracy is better than I am. Say in the .2s at 100 yards off a bench, bipod and rear bag.
For me, it works. Your Mileage May Vary.
Mikecr
Well-Known Member
It's not about powder to bore. Not bore capacity(over/under capacity). The spreadsheet referenced is wrong.
It goes to the ratios such as demonstrated by those patented with the WSSM cartridges. These case ratios lead to different relative amounts burned within a chamber -vs- outside a chamber. And this does equate to a type of efficiency.
I'm sure Ackley described this in his patents, where Gibbs went a different direction.
I guarantee the weighting factors for WSSM cartridges are way lower than that of a 30-06 (just opposite of efficient).
The WSSM wide body high shoulder angles keep pressure in it's chamber(bottle-necking), where a skinny cased 30-06 with it's low shoulder angles shoves a slug of powder down the bore(funneling), adding to bullet mass, and igniting only at muzzle release.
It goes to the ratios such as demonstrated by those patented with the WSSM cartridges. These case ratios lead to different relative amounts burned within a chamber -vs- outside a chamber. And this does equate to a type of efficiency.
I'm sure Ackley described this in his patents, where Gibbs went a different direction.
I guarantee the weighting factors for WSSM cartridges are way lower than that of a 30-06 (just opposite of efficient).
The WSSM wide body high shoulder angles keep pressure in it's chamber(bottle-necking), where a skinny cased 30-06 with it's low shoulder angles shoves a slug of powder down the bore(funneling), adding to bullet mass, and igniting only at muzzle release.
Mikecr
Well-Known Member
It's one little part in calibrating QL to your actual results.
If all other parameters have failed to nail it, and it makes sense, then there is weighting factor to try & test for.
You're right, the default setting begins with a logical median value across a gamut of cartridges. It could change from barrel to barrel, and could only be determined locally.
If all other parameters have failed to nail it, and it makes sense, then there is weighting factor to try & test for.
You're right, the default setting begins with a logical median value across a gamut of cartridges. It could change from barrel to barrel, and could only be determined locally.
ShtrRdy
Well-Known Member
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