deertroy1
Well-Known Member
Agreed, but one's starting load is the others maximum load!
Cooper Rifles and Max Loads
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deertroy1
Well-Known Member
I guess I should have simply ask: what velocity are other 6mm Rem shooters able to reach with 70gr bullets?
Tripodmvr7
Well-Known Member
After running figures through Quick Load I can only say that 3750fps in a 22 inch barrel with a 70gr bullet is seriously testing the red line of the rifle.
deertroy1
Well-Known Member
I weighed the water capacity of 10 fired cases. They averaged 58.07 grains. The weighting factor works out to be 0.39.
Try those inputs and see what you get?
Mikecr
Well-Known Member
The 6mm Rem weighting factor is nowhere near 0.39.
That efficiency number applies with very short/fat/hi shoulder angle cartridges like a WSSM, or something like a 22br AI.
I think you're fudging your numbers incorrectly.
Your powder lot may be different in heat potential, or your chosen barrels may be differing in cross sectional bore area.
That efficiency number applies with very short/fat/hi shoulder angle cartridges like a WSSM, or something like a 22br AI.
I think you're fudging your numbers incorrectly.
Your powder lot may be different in heat potential, or your chosen barrels may be differing in cross sectional bore area.
deertroy1
Well-Known Member
A quick search on the web will give you this formula for calculating the weighting factor:
Cross Sectional Bore Area / Case Capacity of a Case fired in the Rifle * 500
Others that know a lot more than me came up with the formula.
0.045756/58 * 500 = 0.394448
Mikecr
Well-Known Member
No, that's a shade tree overbore index normalized using '500'. The overbore index is useful comparatively only for predicting barrel life.
QL weighting factor functionally defines a bottlenecking attribute of a given cartridge. A rough ratio of how much powder burns in a chamber -vs- further down a bore. QL needs it to assume a certain mass of unburned powder will travel with the bullet as a slug (of added mass).
Think powder funnel; Which cartridge designs efficiently pass powder down bores, and which hold back on that powder.
A WSSM holds powder back to be burned in the chamber, while a 30-06 adds to bullet mass with a great big slug of yet unburned powder against the back of bullets. This slug then flashes at the muzzle, creating a big pressure spike all the way back to the chamber.
The WSSM/WSM cases, set to any capacity, can prove more efficient than .473 case head cartridges of same capacities.
Most .473 case head cartridges of 243win capacity or higher are ~.5, with higher bottlenecking designs dropping the number.
A 6mmRem does not drop the number lower, but actually raises it, as the case body is even longer than 243Win, and there is high body taper, and still a low shoulder angle(even while not quite as low).
This bottlenecking, is also absent in underbores like 30br/6PPC, which is why they reward so much for fastest powders and extreme starting pressure conditions. Without that, much of the powder would just follow the bullet, burning inconsistently later down the bore,, and so much for competitive.
Anyway, you should set weighting factor around 0.55 and recalibrate.
QL weighting factor functionally defines a bottlenecking attribute of a given cartridge. A rough ratio of how much powder burns in a chamber -vs- further down a bore. QL needs it to assume a certain mass of unburned powder will travel with the bullet as a slug (of added mass).
Think powder funnel; Which cartridge designs efficiently pass powder down bores, and which hold back on that powder.
A WSSM holds powder back to be burned in the chamber, while a 30-06 adds to bullet mass with a great big slug of yet unburned powder against the back of bullets. This slug then flashes at the muzzle, creating a big pressure spike all the way back to the chamber.
The WSSM/WSM cases, set to any capacity, can prove more efficient than .473 case head cartridges of same capacities.
Most .473 case head cartridges of 243win capacity or higher are ~.5, with higher bottlenecking designs dropping the number.
A 6mmRem does not drop the number lower, but actually raises it, as the case body is even longer than 243Win, and there is high body taper, and still a low shoulder angle(even while not quite as low).
This bottlenecking, is also absent in underbores like 30br/6PPC, which is why they reward so much for fastest powders and extreme starting pressure conditions. Without that, much of the powder would just follow the bullet, burning inconsistently later down the bore,, and so much for competitive.
Anyway, you should set weighting factor around 0.55 and recalibrate.
deertroy1
Well-Known Member
There's a Facebook group called Quickload OBT. They calculate weighting factor as I described above. I don't have the mathematical background to debate this but there are engineering types on there that do.
You are right that if the weighting factor is changed to 0.55 pressure increases substantially. The load shows no signs of pressure in my Savage. I wouldn't think of trying it in the Cooper.
Also see here. https://www.longrangehunting.com/th...-weighting-factor-formula.136923/#post-962474
You are right that if the weighting factor is changed to 0.55 pressure increases substantially. The load shows no signs of pressure in my Savage. I wouldn't think of trying it in the Cooper.
Also see here. https://www.longrangehunting.com/th...-weighting-factor-formula.136923/#post-962474
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Mikecr
Well-Known Member
Just trying to help.
Internal ballistic software is similar to external in that lying to it doesn't actually pay off.
It may seem to provide what you want, but then fails you under other conditions,, where a better cal would hold.
Internal ballistic software is similar to external in that lying to it doesn't actually pay off.
It may seem to provide what you want, but then fails you under other conditions,, where a better cal would hold.
deertroy1
Well-Known Member
You are helping and I particularly like your insight on Quickload. Your last statement is bang on. I've been reloading for 30 years and have been using Quickload for the last five or so. It has always tracked very well for a variety of calibers and rifles until this one.
