I have been reloading for awhile, but only recently for 10mm. After doing a lot of reading, I settled on 800-x as it seemed to have the most consistent praises for velocity. I was pretty happy as I started, but now am disappointed. My loads from a stock G20 using 180 grain Hornady HAP set at 1.255" OAL and using Federal non-magnum primers: 9.0 grains, 1215fps 9.3 grains 1243fps 9.7 grains 1273fps I was really expecting the 9.7 grains to get me to 1325-1350fps. All were at about 1500' elevation, 90° days. The chrony was about 10' from the bench, except for the 9.7 grain test where it was about 15' away. I don't think that would have more than 10-20fps affect, if that. No evidence of overpressure, so I think I can still go up in powder, but I'm only getting 10fps per 0.1 grain now. I would have to load to 10.3 grains at this rate. So, do I need to back down to 9.0 grains and try magnum primers? I know 800-x is slow, but I haven't seen anything consistent about needing magnum primers to get it's full potential. I don't want this to be a discussion on which powder to use. I want to better understand 800-x and why I don't seem to be getting velocities others are reporting.