Weight-Sorting 222 Rem. Brass and a Surprise

[South Pender]

I've just finished weighing 100 virgin Lapua 222 Rem cases and am surprised. Here's why. Before weighing them, I performed the following case-prep operations:

1. trimmed them to the same length;

2. turned the necks to .0126" neck thickness; this cleaned them all up with close to 100% coverage;

3. trimmed and case-mouth chamfered them with the Forster 3-in-1 tool, giving me a case length of 1.687" ± .001" (the best I could do with the Forster trimmer);

4. uniformed and chamfered the inside of the flash holes.

So my thought was that I had probably brought them closer in weight than they had been before doing operations 1.-4. above. However, I then weighed the 100 cases on my new A&D FX-120i scale (that weighs to .01 gr.). Here are the results:

Heaviest: 94.78 gr.;
Lightest: 92.00 gr.;
Mean of the 100: 93.54 gr.;
Standard Deviation of the 100: .844 gr.

I find this very surprising and a little disturbing. All reports I've seen on Lapua brass have shown very uniform case weights. Here, with a small case, we have a 2.78-gr. spread between heaviest and lightest cases.

Is this a normal result? What are your thoughts?

 

[jlow]

I have not worked with Lapua .222 Rem brass, but I did a weight study with some Lapua and LC11 .223 Rem brass a couple of years ago. This is with new virgin brass and with 100 pieces, the variance was 2.58 grain for the Lapua and 2.36 for the LC11 so nothing spectacular. What I find more consistent with the Lapua is their neck thickness, generally much better than LC.

 

[Syncrowave]

I can't comment on your specific numbers, but I did do the same thing with 100 Lapua 6.5/284 cases.

I ended up segregating them into four groups:
1. The vast majority that weighed somewhere in the middle of the range – These I labeled "most consistent weights" for my money loads.
2. Two smaller groups, taken from the higher and lower ends of the bell curve – these I labeled "second and third most consistent weights" and kept separate.
3. The oddball outliers, maybe half a dozen from the very ends of the bell curve. These I use for fouling shots (and there was one WAY outside the range, which I use only as a "dummy round" reference for size when handloading -- for testing bullet seating depth, etc.)

Your weights should have fallen in a bell-curve distribution. Did they?

Also, I get the feeling that this all (except for the FH deburring) is probably better done after first firing a full-pressure load (after working up to a full-pressure load, of course), to "uniform" them a bit more to your specific chamber and flowing what brass is initially going to flow – and then resizing, neck turning, trimming to length, chamfering, etc. – and then weighing and segregating. My hunch is that they change and flow more between "unfired and first firing" than they do after subsequent firings...

 

[LHSmith]

It's been proven that weight is not necessarily correlated with internal volume.....keeping the combustion chamber as uniform as possible is the important factor.
Lapua up to 3 years ago outsourced their .222 brass and the quality was far from Lapua standards...the outsourced brass was headstamped "222 Rem" , the new in-house brass is stamped "222 Rem Match"
For trim length I don't go below 0.010" of listed max length which would be 1.690" (assuming the chamber is in spec) ....I don't want to loose the ability to increase neck tension, and I don't want a huge gap between the case end and the leade giving a carbon ring a bigger foothold.
Short range BR competitors will get around this brass inconsistency by simply segregating the cases ....and some simply prep them as is......and they still manage to shoot extremely small groups.
If it's for a factory rifle with factory barrel...you'll never see the difference on the target which is all that matters (results)

 

[Scott Harris]

...Here, with a small case, we have a 2.78-gr. spread between heaviest and lightest cases.

Is this a normal result? What are your thoughts?

Yes, that's normal. Lapua makes the best 223 REM brass....period. If you want better, you'll not find it with another brand. If you want a tighter spread, buy more cases to start with. Then you can sort them into smaller batches. Get 1,000 cases for example, and then you can sort your 100ct batches into .2grain increments.

 

[South Pender]

Thanks, guys--valuable advice and certainly reassuring.

Syncrowave: I guess you could say that the distribution is somewhat normal--actually a little skewed positively, but that amount of departure from normality is to be expected.

LHSmith: This is the new Lapua brass with the word "Match" headstamped. I get your point about not over-trimming, and my intention had been to trim them to 1.69". However, after getting the trimmer set up a second time for the Forster 3-in-1 attachment (that inside- and outside-chamfers, as well as trims), I ended up at 1.687" ± .001". The Forster trimmer, in my opinion, is not a great tool; it's just one I've had for a long time, and I didn't want to spend $$ for a better one. It seems to me that securing the cases by the collet arrangement can lead to slightly different results from case to case.

jlow: Your results are very close to mine, and that's reassuring.

Scott Harris and Syncrowave: I plan to further sort these cases. I thought I'd take the extremes at both ends of the weight distribution and set them aside for set-up and foulers, and then sort, say, the middle 80 into two groups of 40 based on weight, with one set of 40 being, on average, heavier--by maybe 1 gr.--than the second set. Then I thought I'd put one group aside (for later use on perhaps a second 222) and work with the other set of 40 cases. I'd then weight-segregate that group of 40 cases into maybe two groups, scratching a line across the base of the cases in one of the two weight groups of 20 cases. I'd then have two sets of 20 cases with pretty similar weights--probably within .4-gr of each other.

Does this seem about right? Overly compulsive?