Quickload 338 Lapua Mag case capacity 108 is wrong?

[secondofangle2]

Why does QL list 108 grains H20 as CC for 338LM? Over several chambers, my fired brass has 116 on the money. It throws off the calculations for the entire cartridge.

 

[straightshooter1]

Why does QL list 108 grains H20 as CC for 338LM? Over several chambers, my fired brass has 116 on the money. It throws off the calculations for the entire cartridge.

It largely depends on the particular brass you're using. The good news is, you can change QL case volume accordingly, like for you it's 116 from the 108 default number.

 

[secondofangle2]

but then the pressure goes down and you have increase the powder charge to get anything near a reasonable pressure/velocity.

Alternatively, if I leave it at 108 grains, and use my current powder charge, it gives a reasonable speed and pressure but the case fill % is well over 100%.

There must be an error somewhere.

And I'd wager that there is not a single 338LM brass with a capacity of only 108 gr H2O. that's like 7% below what my Lapua (thickest/heaviest) case weighs.

 

[918v]

You can also adjust the burn rate of the powder.

 

[RegionRat]

Just a guess, but I'm wondering if that 108 value dates back to converted Rigby cases?

For curiosity, I just checked a few cases here and they averaged....... 116.2

Anyway, I was going to suggest you could pose the question to the support folks at Lapua/Capstone and to QL support and see what they say?

 

[Bmghunter]

but then the pressure goes down and you have increase the powder charge to get anything near a reasonable pressure/velocity.

Alternatively, if I leave it at 108 grains, and use my current powder charge, it gives a reasonable speed and pressure but the case fill % is well over 100%.

There must be an error somewhere.

And I'd wager that there is not a single 338LM brass with a capacity of only 108 gr H2O. that's like 7% below what my Lapua (thickest/heaviest) case weighs.

Adjust the volume and you can even permanently adjust it. Then make sure all of the other measurements match your setup. If the calculations are off at that point, adjust your powder BA burn rate until it predicts matching velocities. Then save that ba value for the burn rate for your lot of powder. You always need to adjust the default values to match your lot of powder as it could change between lots. Also don't ignore the shot start pressure that you can edit also as it also matters.

 

[secondofangle2]

Thanks guys. I’m pretty familiar with most of these nuances of the program.

The thing I am stuck on, is that the case volume in grains of water does not correspond to what percentage of the case is full with a particular bullet and a particular COAL

I understand there are numerous adjustments I can make as you all have enumerated. But this seems a simple matter, right? If I seat a 285 WLD-M to a COAL of 3.775 inches, and I can hear space in there when I shake it, the program should not tell me I have a 104% case fill compressed load

 

[lash]

Your answer is in here in my opinion. Yes, when case capacity is increased, you do have to increase the powder charge to get the same velocity. Unless of course you seat the bullet deeper.

 

[straightshooter1]

Thanks guys. I’m pretty familiar with most of these nuances of the program.

The thing I am stuck on, is that the case volume in grains of water does not correspond to what percentage of the case is full with a particular bullet and a particular COAL

I understand there are numerous adjustments I can make as you all have enumerated. But this seems a simple matter, right? If I seat a 285 WLD-M to a COAL of 3.775 inches, and I can hear space in there when I shake it, the program should not tell me I have a 104% case fill compressed load

Just trying to understand. . .

so, when you adjust Case Capacity to 116 gr H2O, the program is saying your load is 104% "Filled"?

PS: how many grs of what powder?

 

[6.5SH]

Why does QL list 108 grains H20 as CC for 338LM? Over several chambers, my fired brass has 116 on the money. It throws off the calculations for the entire cartridge.

My guess is the data they used was with a bullet seated. Nosler gives water capacity, but it's with the bullet.
Click each weight and you can see the capacity change:

338 Lapua Magnum Load Data

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[Bmghunter]

Let's say you are using h1000 and 85 grains of powder using a Berger 300 grain hybrid. The 108 cc default in QL will show a capacity of 103.8 fill. This is compressed. It gives a velocity of 2457 fps. Change this case to 116 and the case fill is 95.3 and no compressed anymore. The predicted velocity is now 2342 fps. Let's say your actual velocity is 2400fps instead. And let's say all other measurements are correct and your 116 grain cc is correct. Then now you adjust the ba value up until the predicted velocity is about 2400fps. Done.

 

[secondofangle2]

Here it is. 338LM. load cartridge then bullet and it populates with 108gr capacity which is 8 grains or 7% too small.

When I load this into a Lapua fired or resized case, like every other normal person on the planet, that case is 116 gr capacity, and I feel no crunch and there's room when I shake it. The output says I'm 105.8% full which should be a compressed load. It is not.

 

[Bmghunter]

Here it is. 338LM. load cartridge then bullet and it populates with 108gr capacity which is 8 grains or 7% too small.

When I load this into a Lapua fired or resized case, like every other normal person on the planet, that case is 116 gr capacity, and I feel no crunch and there's room when I shake it. The output says I'm 105.8% full which should be a compressed load. It is not.


View attachment 8395504

Isn't this what we all trying to tell you, change the 108 capacity value to your actual value of 116. The filling L.R will adjust, and recalculate. If velocity is wrong at this point, change the burn rate factor ba value.

 

[secondofangle2]

it’s this that I under understand completely

But you are saying to change, not only one clearly erroneous value, but yet another one namely, the burn rate.

If I change enough things, I can get any set of variables to line up. But being a number guy, this approach doesn’t make any sense to me.

Being a predictive program, the point is to take known variables and then extrapolate from there. If we start with one known variable that is erroneous It doesn’t make sense to change another variable - which may be correct - to compensate for the first erroneous variable.

That’s pure nonsense

 

[Bmghunter]

Is the 108cc erroneous? That's possible, but it's also possible it's a correct value for SOME brass out there, specifically the lot the quickload folks used to measure. I don't know which one is it, but the that's why they let you change it.
Maybe you have a loose chamber and after fire forming your brass is 118 grain cc. You will adjust it to 118 even if they put in 116 by default. Point is, it's an adjustable value that you need to match to your lot of components. Not all components will come out with the exact same specs.

 

[straightshooter1]

Here it is. 338LM. load cartridge then bullet and it populates with 108gr capacity which is 8 grains or 7% too small.

When I load this into a Lapua fired or resized case, like every other normal person on the planet, that case is 116 gr capacity, and I feel no crunch and there's room when I shake it. The output says I'm 105.8% full which should be a compressed load. It is not.


View attachment 8395504

With that load, using 116 gr H2O the case fill is at 97.6%; plenty of room for more powder and with an adjustment for powder burn, I don't see any real issue. . . .???

Adjusting burn rate and not temperature to get your velocity of 2888 fps:

 

[45-90]

One of my manuals says 115 grs of water capacity...so your actual case capacity is pretty close, depending on brass and reamer used.

You are supposed to go with YOUR H2O capacity anyway, regardless of what QL has in their library.
It's not an exact calculation, in any event, but predictive software, and an approximation. USE AT YOUR OWN RISK, and always work up.
Not a substitute for loading data manuals, as they state.