Weighing your brass question
- Thread starter powdergun
- Start date
Nope, it doesn't. The chamber only decides the "outside" dimensions.
More brass in the case takes up capacity space, so volume will decrease.
In some situations, such as doing case capacities on milsurp 7.62x51, or Privi 308Win, which is very close to the same spec, then doing capacities on most commercial 308 Win cases and comparing them, the difference is noticeable enough that loading manuals recommend reducing the powder charge substantially.
Same goes with every milsurp case when compared to commercial cases.
For most hand loaders this isn't an issue, as they only use commercial cases. Even then, the differences between two manufacturers of brass can make a difference, especially at close to max load conditions.
OP
The problem that people don't seem to recognize is that to make a determination about the internal volume of a case via the weight of the case, all the cases MUST be EXACTLY the same dimensions. Like every dimension we can alter, must be exactly the same. If not, then all you are doing is measuring the differences in dimensions that are not the same.
Dimensions we can alter are:
External size - cases must be resized
Length - cases must all be trimmed to same length
Primer Pocket - pockets must be reamed
Flash Hole - must be deburred
Until you have done all those things as accurately as possible, weighing the cases won't tell you anything useful about the internal volume. THIS is why weighing cases to determine internal volume is not worth the work.
Jerry is correct
Its a lot of work for little gain.
No it doesn't. The inside of the case sets of the volume.
Incorrect. It needs to be done every time you trim the length or ream the primer pocket, because brass has flowed, which ultimately thins the walls or web and thus alters the internal dimensions and volume of the case.
Your last sentence is correct. However believing something makes a difference doesn't mean it does make a difference.
The problem that people don't seem to recognize is that to make a determination about the internal volume of a case via the weight of the case, all the cases MUST be EXACTLY the same dimensions. Like every dimension we can alter, must be exactly the same. If not, then all you are doing is measuring the differences in dimensions that are not the same.
Dimensions we can alter are:
External size - cases must be resized
Length - cases must all be trimmed to same length
Primer Pocket - pockets must be reamed
Flash Hole - must be deburred
Until you have done all those things as accurately as possible, weighing the cases won't tell you anything useful about the internal volume. THIS is why weighing cases to determine internal volume is not worth the work.
Jerry is correct
Its a lot of work for little gain.
No it doesn't. The inside of the case sets of the volume.
Incorrect. It needs to be done every time you trim the length or ream the primer pocket, because brass has flowed, which ultimately thins the walls or web and thus alters the internal dimensions and volume of the case.
Your last sentence is correct. However believing something makes a difference doesn't mean it does make a difference.
Definitely not necessary for your goals.
And I would further argue if it's a useful procedure for anyone.
It would be interesting to set up a blind test between sorted brass vs non-sorted brass. Line up a good shooter that doesn't know which brass he is shooting, and shoot a bunch of groups and take ES/SD measurements along the way. Do this over many days and see if there is collectively any difference in measurable performance, averaged out across all days of shooting.
And I would further argue if it's a useful procedure for anyone.
It would be interesting to set up a blind test between sorted brass vs non-sorted brass. Line up a good shooter that doesn't know which brass he is shooting, and shoot a bunch of groups and take ES/SD measurements along the way. Do this over many days and see if there is collectively any difference in measurable performance, averaged out across all days of shooting.
You can shorten the process by doing capacity-by-weight comparisons by selecting one or two cases to represent each of the weight groups you have created.
This will be very close over the whole group. This way you don't have to weigh each case.
Weight of brass will have a direct influence on water capacity.
I did those tests, back in the day when I was desperately trying to shoot five countable 10-dot targets in the Hunter Bench Rest competition.
I found there wasn't any noticeable difference in point of impact, with the same load, out to 300 yds.
That was with the cartridge I chose to use for those competitions, which was the 308Win.
As long as the powder charge was consistent, the POI would be consistent. The rifle/scope/ammo combination I was using was accurate enough to show a difference if there was a reason.
For smaller cartridges, such as 22PPC, 223rem, or 6PPC the differences show up a bit faster. Mostly because shooter put as much powder into the case as they can compress into it and still allow the bullet to stay seated.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Checking case volume is super fast and easy.... with fireformed, trimmed to same length, fill with a fine granular powder (H110 or similar).. or just use salt.
With the funnel on the neck, tap the case until it has settled leaving just a hint at the base of the funnel. Remove funnel, scrap top of neck to level... funnel on next case, dump powder in, tap case, see where it ends up... repeat. Try not to spill or just refill first case and then carry on.
A very slight difference in powder level is very visible but would be of little consequence wrt to volume. Say 1mm variation in height in the case neck of a 308win case is squat for volume but really easy to see. Pull any case that has a visibly different level for the powder... I doubt you will find many/any from the same lot of decent manf brass.
As fast as you can pour, tap and look... you have a sorted case.
Done this to sort NATO marked brass in 223... also, LC brass marked the same year. Was really surprised at how well they sorted. This is 1F, sized and prepped by me, fired and then volume sorted
Jerry
With the funnel on the neck, tap the case until it has settled leaving just a hint at the base of the funnel. Remove funnel, scrap top of neck to level... funnel on next case, dump powder in, tap case, see where it ends up... repeat. Try not to spill or just refill first case and then carry on.
A very slight difference in powder level is very visible but would be of little consequence wrt to volume. Say 1mm variation in height in the case neck of a 308win case is squat for volume but really easy to see. Pull any case that has a visibly different level for the powder... I doubt you will find many/any from the same lot of decent manf brass.
As fast as you can pour, tap and look... you have a sorted case.
Done this to sort NATO marked brass in 223... also, LC brass marked the same year. Was really surprised at how well they sorted. This is 1F, sized and prepped by me, fired and then volume sorted
Jerry
- Location
- Blaster land, Okanagan BC
Nice, I’ll remember that one. Thanks for the tip.
