I can provide some assistance but for the best help I recommend that you contact Walt Berger directly at email@example.com
. Walt is the best person to provide you with assistance even if it is not related to the bullet.
Regarding the various loads listed in the manuals, we are putting our manual together right now and have been doing considerable research on the subject of loading data. We have learned that no two manuals are alike because different lots within a particular type of powder will vary considerably. In fact, powders can change places on the burn rate chart due to this inconsistency.
You may have a lot that is hotter than those tested when the manuals were created. If this is the case in your situation then you can see why loading manuals will tend to list loads that are conservative.
It is possible that something else is causing your situation which is why I am suggesting you get Walt involved.