I’m just starting with a new Norinco M14 and plan to see how much of an improvement I can make on the accuracy of the rifle by some tweaking and hand loading. In relation to the latter, I weighed several brands of .308 cases today. The primary purpose of my investigation was to see if I worked up a pet load with some odd brass, if I could go ahead and volume load that recipe into my 500 shiny new LC brass and still expect good results (I already know the answer, but decided to prove it to myself and share the data).
I very quickly confirmed, as suspected, that the answer was a definite "no" as the weights of different brands of case varied widely. It’s pretty safe to say that the heavier cases have thicker walls and therefore a smaller interior volume (I quickly screened case lengths to make sure none were way out of spec). Certainly, as most of us reloading veterans know, load data should not be transferred from one brand of brass to another – and this experiment (I think) illustrates the reason for that very well. As the most extreme example, I measured the average weight of Winchester brass at 164.2 grains while the average weight of Imperial brass is 191.4 grains – a difference of 27.2 grains. A stiff load in a Winchester case would certainly approach dangerous pressures if dumped into an Imperial case. Even if a load were safe in both brands, if you had found the “pet load” for your rifle with one brand of case, you’ve have to tweak the powder charge again if you changed to a different brand of brass to account for a change in the case volume/pressure change.
My case weight data is shown below. All case weights are in grains and include a primer (a spent LR primer weighs approx. 3.3 grains, by the way). 5 cases is a tiny test lot for any serious data, but the general trends are visible in comparing the weights among brands and proving a point to myself.
Lake City: 186.5, 181.2, 185.0, 186.7, 185.8 average 185.0 spread 5.5
Winchester: 165.3, 162.8, 161.6, 170.0, 161.5 average 164.2 spread 8.5
R-P: 167.6, 170.5, 170.6, 167.7, 170.9 average 169.5 spread 3.2
Imperial: 190.9, 191.7, 192.3, 189.9, 192.2 average 191.4 spread 2.3
S&B (only have 3 old ones): 181.2, 177.2, 180.1 average 179.5 spread 4.0
RWS (only have 1): 174.1
Federal (standard): 183.6, 183.4, 181.7, 184.9, 182.9 average 183.3 spread 3.2
Federal GMM: 182.6, 182.6, 182.9, 183.5, 183.2 average 183.0 spread 0.9
With 500 new LC brass in my bucket I’m planning to work with that on this M14 experiment. I had read it is very thick/robust brass, good for M14 use, and the weights do indeed supporter that information (as compared to Winchester or R-P). I’m also under the impression that Lake City and Federal are one in the same so it makes sense that the Federal brass is of very similar weight. In terms of consistency, the Federal GMM is the hands down winner; a testament to the QA/QC that Federal puts into that product. A little weight sorting of the LC brass will help me improve results of course. Even from my tiny sample of 5, all I’d have to do is move the lightest case (181.2 gr.) to my plinking bin and constistency would certainly improve.
It’s also interesting to note that the old Imperial brass is the heaviest of all – likely very good stuff if the hardness were right. Maybe next time I’m walking the rows at a gun show I’ll be on the lookout for some cheap Imperial brass to torture test. LOL
I very quickly confirmed, as suspected, that the answer was a definite "no" as the weights of different brands of case varied widely. It’s pretty safe to say that the heavier cases have thicker walls and therefore a smaller interior volume (I quickly screened case lengths to make sure none were way out of spec). Certainly, as most of us reloading veterans know, load data should not be transferred from one brand of brass to another – and this experiment (I think) illustrates the reason for that very well. As the most extreme example, I measured the average weight of Winchester brass at 164.2 grains while the average weight of Imperial brass is 191.4 grains – a difference of 27.2 grains. A stiff load in a Winchester case would certainly approach dangerous pressures if dumped into an Imperial case. Even if a load were safe in both brands, if you had found the “pet load” for your rifle with one brand of case, you’ve have to tweak the powder charge again if you changed to a different brand of brass to account for a change in the case volume/pressure change.
My case weight data is shown below. All case weights are in grains and include a primer (a spent LR primer weighs approx. 3.3 grains, by the way). 5 cases is a tiny test lot for any serious data, but the general trends are visible in comparing the weights among brands and proving a point to myself.
Lake City: 186.5, 181.2, 185.0, 186.7, 185.8 average 185.0 spread 5.5
Winchester: 165.3, 162.8, 161.6, 170.0, 161.5 average 164.2 spread 8.5
R-P: 167.6, 170.5, 170.6, 167.7, 170.9 average 169.5 spread 3.2
Imperial: 190.9, 191.7, 192.3, 189.9, 192.2 average 191.4 spread 2.3
S&B (only have 3 old ones): 181.2, 177.2, 180.1 average 179.5 spread 4.0
RWS (only have 1): 174.1
Federal (standard): 183.6, 183.4, 181.7, 184.9, 182.9 average 183.3 spread 3.2
Federal GMM: 182.6, 182.6, 182.9, 183.5, 183.2 average 183.0 spread 0.9
With 500 new LC brass in my bucket I’m planning to work with that on this M14 experiment. I had read it is very thick/robust brass, good for M14 use, and the weights do indeed supporter that information (as compared to Winchester or R-P). I’m also under the impression that Lake City and Federal are one in the same so it makes sense that the Federal brass is of very similar weight. In terms of consistency, the Federal GMM is the hands down winner; a testament to the QA/QC that Federal puts into that product. A little weight sorting of the LC brass will help me improve results of course. Even from my tiny sample of 5, all I’d have to do is move the lightest case (181.2 gr.) to my plinking bin and constistency would certainly improve.
It’s also interesting to note that the old Imperial brass is the heaviest of all – likely very good stuff if the hardness were right. Maybe next time I’m walking the rows at a gun show I’ll be on the lookout for some cheap Imperial brass to torture test. LOL
I didn't have any Lapua, Norma, Nosler, IVI, Hornady or other brass on hand to weigh. If anyone does, please feel free to add that data and satisfy my curisoity.
