There is a lot of talk on reloading forums about bonded/mono bullets and the older style bullets even the partition, It seems for the most part copper/bonded bullets like to be seated off the lands farther than cup and core bullets. But if your not reloading and can't play with length best to stay with what's working, at least until you can range test others. My son has a 270wsm and it won't shoot Barnes bullets but loves AB's so I need to see if seating the Barnes a little deeper will help.