Thread: Size and Weight Sorting For New Brass

It's sometimes recommended that we sort new brass by weight and either batch them for use or discard outliers. Fred Sinclair and Bill Gravatt [ref 1], expected to reject about 25% on visual inspection, then aimed for a total weight range of < 1.5% across their working set of brass. They said to do this before any length trimming, flash hole or primer pocket uniforming.

I checked my batch of 200 new Lapua 6.5 Grendel cases:
I couldn't see any visible defects like neck damage, dents, chips or flash hole burrs.

Weights

Case Wt (gr) Number of Cases
110.0 2
110.1 4
110.2 7
110.3 9
110.4 9
110.5 9
110.6 10
110.7 21
110.8 26
110.9 24
111.0 23
111.1 24
111.2 17
111.3 9
111.4 4
111.5 2

Total range: 1.5 gr = 1.5%
By culling away the 22 cases <= 110.3 and >= 111.4, all remaining cases were within a range of 1.0 gr.

Would it have been better to size and trim them all to length, ream flash holes, deburr them and cut the primer pockets before weighing ?
So, I measured a selection of 10 cases having a range of weights to see whether perhaps the heavier ones were so due to being longer or perhaps the neck thickness would be the cause of heavier or lighter brass overall. There could be other dimensions that might be of interest - suggestions welcome ! Also suggestions and critique of the correct way to measure these dimensions, please .

Measuring neck thickness at 4 places:

I found that most measurements were 0.0140" (measuring to 0.0005") and most cases had one, sometimes two quadrants which were +/- 0.001".

Measuring cartridge length:

Lengths ranged from 1.5130 to 1.5160" and there was no trend with weight.
SAAMI 1.500 - 1.520"

Checking cartridge headspace dimension on the shoulder at 0.350" diameter.
This is a Hornady Case Headspace guage.

Range 1.2040 - 1.2050"
SAAMI 1.213 - 1.220"

Primer pocket depths (best of 3 for each case)

I used the end of the slider shown on the right of this photo.

0.1230 - 0.1240"
SAAMI 0.117 - 0.123"

Here is the summary in my log book:

I reweighed the cases and found they came back +/- 0.1 gr.

My conclusion was that variations in case dimension didn't explain the variation in weight, so trimming and pocket cutting wouldn't normalise the weights of otlier cartridges. I also doubt whether traditional case prep like cutting the pockets, trimming to length, chamfering case mouth or flash holes is actually beneficial on new brass.

I'm wondering what is current thinking on preparing new brass, nowdays ?

ref 1 Sinclair F, Gravatt B "An overview of reloading for extreme accuracy" in Brennan D The Precision Shooting Reloading Gide Precision Shooting Inc 1995.