I had a standard 260 with a "match" cut chamber , I used 308 Lapua brass necked down and I had to turn the necks just enought to clean them up to 100% then they fit perfect , so I was getting the bennifits of a tight neck but still able to shoot factroy ammo if needed. I'm not to sure what all you would gain from going witht he Ai chamber maybe a bit more velocity and limited case streach neither of which I had any trouble with , even with the shorter 308 size case if the gun is chambered with a long throat for the 140 class VLD's so that they aren't stuck down in the case then its a good idea to have a Wyatt's box installed.
OR
the 6.5x47Lapua is a great little round and velocity wise gives up very little if any to the 260 and Ai version all with smaller case , better feeding and less powder. I know that this case necked down to 6mm will run with the 243 and 243 Ackley even shooting 115gr bullets. Its track record for accuracy is steady improveing as more folks shoot this round.
