Case weight vs. powder charge

[mcxring]

Hey Guys,
Ive just started to understand and experiment how case weight affects accuracy, to save myself alot of testing (which im sure ill do anyways) Im sure it would depend on what powder used, but does anyone know how much less powder you would use, if any, in a case that weighs 92 grain vs one that weighs 91,. And thanks for all the great advise on the trigger assembly, ordered a SSA-E gieselle this morning.
Mike

 

[fredhorace77]

imo theres really no telling without just checking it yourself...alot depends on where that 1 grain difference is at..could be in neck wall thickness or the case rim...which in either place wouldnt affect how much powder it will hold. only if the difference in weight is in the case body itself..

 

[Keith Glasscock]

Rather than weight, check the internal volume. The powder charge is more linear from that measurement in my opinion.

Having said that, each cartridge will behave differently and you just have to work things up.

 

[fredhorace77]

Rather than weight, check the internal volume. The powder charge is more linear from that measurement in my opinion.

Having said that, each cartridge will behave differently and you just have to work things up.

this is exactly what ive been arguing with someone about whom keeps pm me to tell me that im wrong...thanks for setting the record straight

 

[Ackman]

Hey Guys,
Ive just started to understand and experiment how case weight affects accuracy, to save myself alot of testing (which im sure ill do anyways) Im sure it would depend on what powder used, but does anyone know how much less powder you would use, if any, in a case that weighs 92 grain vs one that weighs 91,. And thanks for all the great advise on the trigger assembly, ordered a SSA-E gieselle this morning.
Mike

It has nothing to do with which powder. And you can't go by case weight. The 91gr case could easily have more internal volume than a 92gr case.......it's about where the extra brass is distributed on the case. Weigh some brass shavings and see just what a very tiny volume it takes to make 1grain.

 

[fredhorace77]

Hey Guys,
Ive just started to understand and experiment how case weight affects accuracy, to save myself alot of testing (which im sure ill do anyways) Im sure it would depend on what powder used, but does anyone know how much less powder you would use, if any, in a case that weighs 92 grain vs one that weighs 91,. And thanks for all the great advise on the trigger assembly, ordered a SSA-E gieselle this morning.
Mike

It has nothing to do with which powder. And you can't go by case weight. The 91gr case could easily have more internal volume than a 92gr case.......it's about where the extra brass is distributed on the case. Weigh some brass shavings and see just what a very tiny volume it takes to make 1grain.

thank you again...you are exactly right...

 

[mikecr]

Weighing cases come about as all shortcuts do: because it's rare that people would expend efforts otherwise.
And if they did measure actual volume(by some miracle), they probably would not measure every case, but would measure only a few, having adopted assumptions about the rest..

It's a sad reality of our failed human revision.

 

[amlevin]

Several times over the past 10-years I have segregated brass by volume. I do it ONLY after the brass has been fired twice, fully prepped, and trimmed. I do it with ball powder (H380) and feel there are to many inconsistencies when using water/liquid. I have done it with 243 / 6PPC / 6BR / 30-WSM / 300-WM brass.
What I repeatedly find/found is external case weight has no definite baring on internal volume.
I also find more times then not, the internal volumes have tighter percentages (%) then by external weight.

One extreme example I remember well: I had one lot (100 pieces) of 243 Winchester brass that the case weight extremes was a 4.2-grain spread, but the case capacity of the two extremes were less then 0.2-tenths in volume.
And the two worse by volume extreme were 0.8-tenths but the case weights of those two were only 0.4-tenths.

Happy Shooting
Donovan Moran

The more thought I give to "case weight" versus volume measurement, the more questions I have.

For Case Weight Segregation to make sense to me, it would require that all cases have the same level of cleanliness, same shapes (when sized), same trim length, same primer pocket depths, same sized extractor grooves, rims, etc. When taking into consiideration that there might even be some variation in the composition of the bras, adding all the tolerances could result in the differences in case weight observed, regardless of the actual case volume.

I can appreciate the theory that a basic case with more weight means thicker walls/web and therefore has to have a reduced volume but does it really? Is it just possible that those who weigh cases are that much more meticulous in all other aspects of their reloading and the results are attributed to "case weighing"???

Even measuring volume with a liquid has it's limitations. Unless using a non-Newtonian fluid, or a device that makes sure the "dome" is uniform, there can be wide variations of volume measurement as well. Considering that a normal "drop" of water weighs .003 ounces or 1.3125 grains, the whole process can lead to an "Excedrin Headache" or "Maalox Moment" :-\ :-\

 

[XTR]

The biggest variation in weight in WW brass is caused by different extractor ring cuts. One of the BR shooters I see at the range from time to time once told me that sorting cases by weight gains you nothing. If you want to make a difference you have to measure internal volume, and as stated above, that has a much higher consistency.

If you aren't shooting BR I'd never sort cases, if you are, then I'd get the rest of my loading routine down before I went there.

Personally, I debur flash holes, uniform primer pockets, and trim after they are once fired. I don't turn necks, and I use a Lee collet sizer. Two weeks ago I shot a 1000 yard match with pointed Hornady 178s in virgin WW brass. My 20 shot for record at 1000 yards were all w/i 3/4MOA vertical, and I'd bet that part of that 3/4 was me and mirage. (I shot on a clean target then we had a pit change so the only shots on target were mine)

Do you need better than that? The only reason I can think of is shooting BR.

 

[mikecr]

Do you need better than that? The only reason I can think of is shooting BR.

Well, shooting 3/4moa without matching case volume is hardly a basis one way or another -for anything really. And there are even more reasons to improve reloading beyond bench rest shooting.
Is it so easy to get a factory hunting gun shooting 3/4moa, or 1/2, or 1/4, that extra measures are only needed for a BR gun?
I don't think so.

amlevin, about the only thing dry case weighing is doing is helping find flash hole chads.
Once you learn how to best measure H20 capacity, it's not difficult at all(no rocket science).