6.5x55 AI (40 degree)

As much of a barrel burner as the 6.5/284 but without the opporunities...
Need the long action to really make the 6.5/284 shine in the bullet seating dept, unless single-loading...

The .260rem is about the optimum for 6.5mm performance & barrel life Unless you go slower...
 
I'm surprised to hear that it's a barrel burner considering it's using less powder and has theimproved shoulder, which theoretically should increase Barrel life over the standard caliber.