I went through my normal process of working up loads, using plated 200gn and 230gn RN bullets. With the 200gn bullets (seated to 1.245") I had a charge range of 5.4 to 6.2, and with the 230gn bullets (seated to 1.260") a range of 4.8 to 5.6. For my initial loads, I used large primer brass and Winchester WLP primers. Nothing out of the ordinary during the testing, except I noticed the standard deviation was not as good as I was hoping, anywhere from 24.0 to 48.3. Then I moved to further testing, to compare results with various primer types. The first batches were 200gn bullets and 6.2gn powder, using Winchester WLP and CCI-300 large primers, along with Winchester WSP, Winchester WSPM, CCI-500, and CCI-550 primers. The results were not what I expected. There was a very large difference in velocity between the WLP and WSP primers, nearly 200fps. Also, the CCI-550 small magnums were actually slower than the CCI-500 small regular primers. I thought I must have made a mistake when I labeled the rounds, and got them mixed up. So, I made yet another batch and was careful to check drop weights and properly label/mark the primers. I also loaded two different lots of CCI-550 primers. Here is what I got: RMR 200gn RN bullets, seated to 1.245", 6.2gn Sport Pistol powder. 10 rounds each. Measured with a Labradar, outdoor range with target at 25 yards. Winchester WLP, 797fps, 40.2sd, 132.7es. Winchester WSP, 545.2fps, 66.6sd, 224es. (first round did not eject). Winchester WSPM, 839.8fps, 49.9sd, 146.7es. CCI-500, 746.0fps, 63.8sd, 206.1es. CCI-550 Lot# E01V22, 682.8fps, 65.6sd, 219.5es. CCI-550 Lot# H07V42, 731.3fps, 76.1sd, 247.8es. Rem 6.5, 713.1fps, 52.7sd, 163.8es. (Remington small rifle primers) Clearly, this powder is sensitive to primer types, more than any other powder I have tried. But I have to believe that the large extreme spreads may possibly be from case position sensitivity, as the powder does not completely fill the empty space in the case when the bullet is seated. I will do more testing in 38spl to see if this is the case, doing my usual powder-forward test (hold the gun barrel-down before bringing it up on target). I initially tested the loads at an indoor range with a Labradar, and thought that the ceiling baffles may have been causing problems with the signal reflecting back from the bullets. So, I tested with my Caldwell optical chrono at the outdoor range, along with the Labradar for the final measurements listed above. Since I was initially having doubts about the validity of the chrono readings, I have decided that in the future I will have a known load that I will use as a control group, to verify the test setup, before I test any unknown loads.