Changes between powder lots can happen, and from what I can gather the only way to know for sure and correct it is with a chronograph.Fire five or ten of your sweetheart loads through and record velocities as well as temp, humidity and wind, then try a few test loads with new batch of powder and check velocity and accuracy again in the same way.If you get a higher or lower reading and different accuracy between lots, you can CAREFULLY adjust your load back to that sweet spot.One note though, still respect the max loads in the manuals. Chronographs are actually not too expensive, I think mine was $150 or $160. It's a Shooting chrony and I can't imagine reloading without the benefit of one.Sometimes manuals are overly optimistic about the velocities of a load, though your barrel and chamber will certainly be slightly different than the test rifle used, thus a different pressure and velocity.
