Maybe "Guidelines" rather than rules would be better. I have a new Merkel double rifle drilling in 9.3X74R/20GA 3" that was regulated for 232 grain Norma Vulkan bullets. I have Norma's factory duplication load also (N203B ), so I can work up a load that should get close. But that won't satisfy me, of course. So if I use heavier or lighter bullets, and it doesn't shoot together or to the sights, how do I proceed? If the barrels shoot apart, do I increase velocity to get them to merge? If they cross, do I reduce velocity? Will a heavier or lighter bullet shoot higher or lower? If I change velocity does the POI strike lower or higher? I did some internet searched and didn't find anything. Are there general guidelines on this subject? And then there is the shotgun barrel and slug/buckshot loads..The possibilities are endless....Thanks. Allan
