After a fine lunch, thanks Russel, I got back to my notes which revealed the following. Mostly I have weighed a sample of each batch of cases feeling that case weight gives a good indication of capacity. With the most current samples of R-P, Winchester and Lapua weight with primer varies from 170 to 176 grains with Lapua at the heavier end. This would equate to less than 1 grain of powder. Norma (an old batch) averaged 165 grains and Federal together with some LC 79 and 81 cases averaged 183 grains. Older WW-Super and WW cases were lighter than current Winchester cases at around 160 grains. So what does all this mean? With the middle batch, R-P, Win and Lapua, there should not be much change in pressure or velocity. With the outliers some adjustment is likely to be needed to achieve the same velocity. What I would do is to load a small batch, say 3, with a charge 2 grains under your current load, with each case keeping everything the same other than the case. Chronograph the loads on the same day and set up. If the differences in velocity are minimal then so is pressure. If not then a small adjustment in charge should bring them into line. In any case do check the actual weight of a sample of both your current and new cases as cases change over time.
Regards Grandpamac.
Bookmarks