Re: 6.5x55 and 6.5x55 AI
Don't forget though, some of the best benefits aren't on the performance side but have to do with increased barrel/throat life, longer case life, and more consistent burns. All very good things in addition to the potential velocity gains. And with the PO you can shoot the standard cartridge in the new chamber to fire form and usually still get fine accuracy. With Ackley improvements the datum line stays the same for head-spacing. This makes fire forming very easy and also allows the use of store bought ammo if needed.