Some Lapua Palma H20 capacities

[LVLAaron]

Starting to work my way through some of the finer details of QuickLoad. Decided to check H20 capacity on 5 random fired cases from my FTR rifle.

    Fired (DRY)    Fired (filled)    H20 Cap.
CASE 1     176.6    232.5    55.9
CASE 2     176.8    232.7    55.9
CASE 3    176.9    232.8    55.9
CASE 4    176.7    232.6    55.9
CASE 5    176.3    232.2    55.9

I found it interesting and validating that case capacity was exactly the same despite the .6 grain variation in case weight.

 

[spclark]

What brand of cases?

 

[LVLAaron]

What brand of cases?

Lapua Palma (Lapua 308 small primer)

 

[Ned Ludd]

Variance in case diameter and/or base to shoulder measurements will change internal volume without affecting brass weight. Variance in the dimensions of the extractor groove or primer pocket can also affect case volume differentially from case weight. Finally, when you determine water volume, it is essential to get rid of any and all bubbles inside the case, which may also contribute to apparent case volume variance without affecting case weight.

With all those considerations taken into account, a graph of case weight versus case volume will typically exhibit a trend line with a negative slope, meaning as the cases get lighter, they generally have greater internal volume and vice versa. The problem with sorting cases by weight in lieu of actual volume measurements lies in how many are off the trend line and by how far. The more frequent and severe the outliers, the less useful the process of sorting cases by weight. You can see a few data points in the graph below where cases of approximately the same weight exhibited internal volume variance of about 0.1 gr. You can see even more points where cases of approximately the same volume exhibited case weight variance of up to 1.0 gr or more.

 

[Dusty Stevens]

The extractor groove is where your difference is

 

[seymour fish]

Starting to work my way through some of the finer details of QuickLoad. Decided to check H20 capacity on 5 random fired cases from my FTR rifle.

    Fired (DRY)    Fired (filled)    H20 Cap.
CASE 1     176.6    232.5    55.9
CASE 2     176.8    232.7    55.9
CASE 3    176.9    232.8    55.9
CASE 4    176.7    232.6    55.9
CASE 5    176.3    232.2    55.9

I found it interesting and validating that case capacity was exactly the same despite the .6 grain variation in case weight.

Yep. Have found exactly the same thing repeatedly, with Lapua

 

[LVLAaron]

Yep. Have found exactly the same thing repeatedly, with Lapua

Hah. I feel bad now, I just ordered 500ct Alpha Munitions. Looking forward to running some data on them. Never seen anyone post H20 weights anywhere for them.