I have a 65x06 that was built around a 140gr Hornady Spire Point seated out so the base of the bullet was seated right at the junction of the neck and shoulder. Worked out very well! I've gone ahead and tried 129gr Hornady's in it and they do shoot very well but the 140gr will out shoot them. Best strictly from accuracy point is the 140gr MK. I think if I was to ever have another rifle built it would be built around a certain weight bullet. I like bullet's seated to the base of the neck. Got into that years ago with a 7mm Rm Mag. Old Sako L61 thaut not as good as the 139 t was great with 139gr bullet's but up around 160gr still shot well but not as well as th 139gr. I figured loading out the old 160gr Speer Hot Core the same way might improve it. Made up a dummy round and had a gunsmith in Kalispell, Montana fit it to the chamber. What a difference! Accuracy was absolutely terrific and something I didn't expect, amount of powder went way up. From a load of 67grs of N205 I went up to 59grs. No idea of velocities as back them we didn't have chronographs like we do now. I've found over the years that my best loads came either just off the lands or bullet seated to the base of the neck if I could do it. In my present 65x55, I can't reach the lands and two ways it shoot great is to the base of the neck and one bullet dia into the case. I think all the 6.5x55 chamber's are long like that and would guess it's because the European's preferred the long bullet's in it!
