30-06 Case capacity - Rem vs Win - H2O Volume question

TheCanAm

TheCanAm

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I made some great reloads last Fall which gave me consistent sub-MOA groups out of my old hunting rifle. I had used once-fired factory brass from Federal and Remington. Over the winter I ordered some Winchester brass because I heard such good comments, then resized, primed and reloaded. They gave me aweful results around 3-4" groups. It could be because I FL resized them the first time through, where as I neck resized the once-fired brass. However, I tested two batches last fall - one FL, one Neck - and I only saw about a 1/2"-3/4" difference in the groups. So I thought I should check the case capacity. Below you will see me scribbling:

RP%20vs%20Win%20brass%20volume_sml.jpg


Bear in mind, I only had the patience to measure a single case of RP and Win. When filled with water, the difference is only ~1.1 grains. After some math, I calculated that translates to 3.66 drops = .23 cubic cm. Using the Lee Volume Measure Density Chart that comes with the Lee Perfect Powder Measure, I looked at the volume of H4831 and I calculated that .23 CC would allow an extra 3.17 grains (+/- .86 gr). The .86 variance comes from allowing for 1 drop of water more or less between the cases when measuring.

Question 1) Do you see anything wrong with how I measured?
Question 2) How much difference would this small variance actually make? (i.e. Can I blame the capacity difference, or should I look at other factors?)
 
I can't help really but in my 2506 with the same load the rem brass loads are 120fps faster and flattened primers. The ww brass primers were fine. My 4570 has the same result. WW has a greater case capacity over Remington brass
 
From Quickload

Case capacity 68 grains of water, 180 grain bullet, 59.7 grains H-4831 chamber pressure 59,944 psi.

Case capacity 66.9 grains of water, 180 grain bullet, 59.7 grains H-4831 chamber pressure 63,117 psi

Three things happened with your Winchester cases, 1. different case capacity changed chamber pressures, 2. Winchester case weight and internal volume vary more than any other brand of case, 3. the necks were thinner and they changed your neck tension. Bottom line your "NEW" Winchester cases need another work up load like you did with your other cases.

Below, the only reference I could find were .223/5.56 cases but below you can see Winchester has the widest case weight variance. Meaning the Winchester cases would have the biggest velocity spread (ES and SD)





NOTE: I edited my post and case capacity figures above it was 69.1 and was changed to 66.9, meaning less case capacity = higher chamber pressure.
 
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Full length sizing new cases is really the same as neck sizing once fired cases as new brass is undersized to fit in any chamber. You can full length size new brass without any lube. Not that this has anything to do with your issue its just something that came to mind when I read your post
 
FYI: I took some fired-formed W-W cases, neck sized them, and checked 4 of them. They average 69.9 (69.8, 69.8, 69.7, 70.1), so 1.6 grains of H2O difference. That would be substantial considering the 1.1 gr difference you calculated resulted in ~3,200 psi change. I did not realize it would be so significant since I had always used once-fired brass from my rifle and never bought new brass.

Side note: If there is so much variation in W-W case capacities, why have I always heard "Buy Winchester brass. Next to Lapua, it's the next base thing and more affordable?" Will I reap the results of some inherent qualities after it's fire-formed, or did I waste good money?
 
If you stick with the win brass those individual once fired case capacities will not make any noticeable difference but if you mix your loads with other brands of brass you probably will see some variance. I think you would have to have to get into bushing sizing your loads and messing with neck tension to even start to see any difference with the win brass
 
I discovered the difference in case volume by mixing brass and getting terrible groups. It's nice to see it spelled out on paper. Now I sort brass and work up for each type.
 
.284 said:
I think I covered that by mentioning that new brass is undersized but thanks for clearing up the obvious
Click to expand...

Well, it's not undersized by the standard; usually, new brass is sized closer to the allowed minimum but (must be) always ABOVE this minimum.
 
What do others consider is an acceptable range of capacity?

Most of my W-W brass is falling between 69.8 to 70.2 grains of H2O. I get a few outliers like 70.6 and 69.2.

How picky should I be? +/- 0.2?
 
TheCanAm said:
What do others consider is an acceptable range of capacity?

Most of my W-W brass is falling between 69.8 to 70.2 grains of H2O. I get a few outliers like 70.6 and 69.2.

How picky should I be? +/- 0.2?
Click to expand...

Ever thought about weighing the cases empty instead of full of water? Sort them into groups from lightest to heaviest, then prime them load them and shoot them. Or since you already have some great loads with other brass, why bother messin with Win. brass? FS
 
Fassteel said:
Ever thought about weighing the cases empty instead of full of water? Sort them into groups from lightest to heaviest, then prime them load them and shoot them. Or since you already have some great loads with other brass, why bother messin with Win. brass? FS
Click to expand...

Tried that. It is not reliable.
The trouble is that case weight does not necessarily correlate to internal volume. Example: I weighed a heavier case that had roughly the same volume/capacity. A case may have a thicker head for instance.

Edit: I am in my reloading room. Just weighed 2 W-W cases, 264.3 & 261.3 Three grains is significant!
FS, you would likely put those in two different piles but they have the same internal capacity - 70.0 gr H2O.
You're right about that last part though: I had great loads. I shot them all and had already invested in the brass before I realized the good thing I already had. I'll reload those also and compare.

My question still remains: what is an acceptable tolerance for case capacity?
 
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