Posted a question months ago and no one really knew, so here's what I have just found:
Old FC .308 a friend gave me from range pick-up, once-fired in bolt guns:
Smaller "FC" headstamp.
Lightest 12 were from 161.6 gr to 163.2 gr, fired with primers still in. Water capacity from my chamber (might have been the OLD barrel...) averaged 57.729 grains.
Newer FC bought summer of 2008 or '09 from a Member here on the Hide, once-fired from his bolt gun:
Larger "FC" headstamp, bottoms of letters visibly flat/square.
Heaviest were from 183.0 to 183.6 grains, same deal, fired with primers still in. Water capacity averaged 55.714 grains.
So, that 20.5-grain difference amounted to 2.014 grains water capacity difference.
Notably, the light ones were clustered between 161.6 and 171.4 grains. Many of them are still loaded in my cheapo blasting ammo. Only 66 of these lightweights empty right now.
There's a gap in weights between that batch and the heavier stuff, picking up at 177.3 grains empty. 5.9 grains of "range" just not there in the distribution.
Now, off to QuickLOAD to see how that's predicted to affect my charge weights and velocities.
For point of reference, both FGMM and Hornady Match ammo ran a maximum range of 1.1 grains between heaviest and lightest fired cases in one box each, and the Hornady water capacity was 57.83 grains. That makes me wonder whether the sort into 2.0 grain increment batches from the Reloading 101 thread is tight enough. It also makes me want to revisit some earlier load development, where I *thought* that neck turning was making no difference...Un-processed FGMM ammo was doing better than mine, with "more" done to mine with flash holes and trimming and neck turning, but that might not mean squat if my cases were at, say, four times the weight variation of FGMM.
Any thoughts?
Later,
Grump
Old FC .308 a friend gave me from range pick-up, once-fired in bolt guns:
Smaller "FC" headstamp.
Lightest 12 were from 161.6 gr to 163.2 gr, fired with primers still in. Water capacity from my chamber (might have been the OLD barrel...) averaged 57.729 grains.
Newer FC bought summer of 2008 or '09 from a Member here on the Hide, once-fired from his bolt gun:
Larger "FC" headstamp, bottoms of letters visibly flat/square.
Heaviest were from 183.0 to 183.6 grains, same deal, fired with primers still in. Water capacity averaged 55.714 grains.
So, that 20.5-grain difference amounted to 2.014 grains water capacity difference.
Notably, the light ones were clustered between 161.6 and 171.4 grains. Many of them are still loaded in my cheapo blasting ammo. Only 66 of these lightweights empty right now.
There's a gap in weights between that batch and the heavier stuff, picking up at 177.3 grains empty. 5.9 grains of "range" just not there in the distribution.
Now, off to QuickLOAD to see how that's predicted to affect my charge weights and velocities.
For point of reference, both FGMM and Hornady Match ammo ran a maximum range of 1.1 grains between heaviest and lightest fired cases in one box each, and the Hornady water capacity was 57.83 grains. That makes me wonder whether the sort into 2.0 grain increment batches from the Reloading 101 thread is tight enough. It also makes me want to revisit some earlier load development, where I *thought* that neck turning was making no difference...Un-processed FGMM ammo was doing better than mine, with "more" done to mine with flash holes and trimming and neck turning, but that might not mean squat if my cases were at, say, four times the weight variation of FGMM.
Any thoughts?
Later,
Grump
