Re: Hand loading for Long range 1: brass case prep
Great thread. Here's my contribution.
I use a different technique from those described here to set up my resizing dies using Larry Willis' "Digital Headspace Gauge". To set it up for a .002" bump on the shoulder I use the following procedure:
1. I take a case fire formed in my firearm. The case should be a tight fit so that it's as close as possible to chamber dimensions.
2. Set the case in the Digital Headspace Gauge and zero the gauge (can use Hornady or RCBS gauges). Here's the link:
http://www.larrywillis.com/
3. Insert a .003" shim on the FL or redding body die and screw the die in the press till it's snug on the shellholder. Here's the link for the set of shims:
http://www.sinclairintl.com/.aspx/sid=65249/sku/Skip_s_die_shim_kit____7_8_14_
4. Resize the case with that set up.
5. Place the case in the Digital Headspace Gauge and get a measurement of the amount of shoulder bump.
6. If the bump measures .005" all you need to do is replace the .003" shim with a .006" shim and you get a .002" bump.
The beauty of this set up is that you don't need to touch the die even if you have multiple guns of the same caliber - you just change the shim in accordance with the bump you need. Also you can use another shim if you want more or less bump.
Occasionally, you get a minimal dimension chamber where you can only get less than .001" with the FL or body die. When this occurs, I use a dedicated shell holder which I sand on a flat surface to take off .001" or so.
As regards case triage I believe that weighting cases on the assumption that there is a constant correlation between case weight and internal volume is a complete waste of time that is based on an erroneous assumption. Others factors such as dimension of base and extractor groove are significant confounding variables.
With new brass, I expand necks to uniform size, turn them for uniform thickness, trim to uniform length, chamfer, clean primer pockets and deburr primer holes. After fireforming, I routinely measure internal volume of 30 cases in order to adjust Quickload parameters to customize it my firearm. I have done hundreds of these measurements and I have found that even with the best of brass (Lapua), the correlation between case weight and internal volume is extremely weak and typically less than 50% valid.
To illustrate the point here's a sample of 30 fireformed Remington cases in my 338 Edge. All cases have been prepped as described above. The empty and water-filled cases were weighted on an Acculab VIC 303 that is accurate within .001 gram or .02 grain.
#.....Case weight (grs)……Var. %……..Water weight (grs)….Var. %
1…….272.68……………………-1.19%.............116.66…………….-0.04%
2…….276.74……………………+0.28%............117.00…………….+0 .25%
3…….272.68……………………-1.19%.............117.10…………….+0.34%
4…….267.24……………………-3.16%.............117.48…………….+0.66%
5…….278.84……………………+1.04%............116.18…………….-0.45%
6…….276.24……………………+0.10%............116.62…………….-0.07%
7…….278.14……………………+0.79%............116.12…………….-0.50%
8…….276.22……………………+0.09%............116.56…………….-0.13%
9…….280.58……………………+1.67%............116.24…………….-0.40%
10…..276.48……………………+0.19%............116.40…………….-0.26%
11…..276.58……………………+0.22%............116.50…………….-0.18%
12…..276.76……………………+0.29%............116.64…………….-0.06%
13…..279.64……………………+1.33%............116.64…………….-0.06%
14…..278.16……………………+0.80%............116.80……………+0 .08%
15…..277.18……………………+0.44%............116.78……………+0 .06%
16…..277.60……………………+0.59%............116.64…………….-0.06%
17…..275.82……………………-0.05%.............116.82……………+0.10%
18…..271.74……………………-1.53%.............117.20……………+0.42%
19…..276.40……………………+0.16%............116.72……………+0 .01%
20…..271.68……………………-1.55%.............116.86……………+0.13%
21…..275.62……………………-0.12%.............116.94……………+0.20%
22…..276.32……………………+0.13%............117.22……………+0 .44%
23…..276.00……………………+0.01%............116.96…………... .+0.22%
24…..278.02……………………+0.75%............116.74……………+0 .03%
25…..273.90……………………-0.75%.............116.54…………….-0.14%
26…..278.00…………………..+0.74%............116.52…………….-0.16%
27…..275.60……………………-0.13%.............116.10…………….-0.52%
28…..276.62……………………+0.24%............116.74……………+0 .03%
29…..275.44……………………-0.19%.............116.74……………+0.03%
30…..275.94……………………-0.01%.............116.72……………+0.01%
Ave..275.96………………………..…………………....116.71
Using the 0.5% variation standard normally advocated (+ or - 0.25% from average), one would have selected 13 of the 30 weighted cases. Selecting by internal volume would have resulted in 20 retained cases. Moreover, 3 of the cases selected by weight would have been rejected by volume (#10, 22 and 27). Consequently, selecting by weight would have resulted in the identification of 10 of the 20 cases that had relatively uniform internal volume.
If one looks at the validity of the assumption of case weight as an indicator of internal volume within a 0.5% variation, it would appear that the assumption is dubious at best. For example, you would expect case #1 which weights 1.19% less than the average of 30 cases to have approximately 1.2% greater internal volume than the average volume for the same cases. Instead, that case is almost perfectly on the mark for case volume (-0.04%). Indeed the correlation is valid only for 11 of 30 cases (#6, 8, 10-12, 17, 19, 21, 23, 29 and 30) or 36.7%.
Another interesting observation from the table above, is that the weight variation among cases is quite large (-3.16% to + 1.67% = 4.83%), whereas the internal volume is relatively constant (+0.66% to -0.52% = 1.18%).
I and 2 of my shooting buddies have run this same experiment independently with hundreds of cases, using 5 different brands of brass (WW, RP nickel, RP, Hor., Lapua and FC) and 6 calibers (223 Rem, 6.5x284, 308 Win. 300 WM, 338 WM,338 Edge) and have come to the same conclusion. That is, if you wish to sort brass for consistency, do it by measuring internal volume.
Finally I agree that sorting cases by measuring neck thickness is an important step in achieving optimal accuracy. I routinely sort my cases with with a digital thickness gauge and only retain those within .001" tolerance.
I apologize for the long post.