Looking for a good long range bullet for both my 264 wm and 260 rem

I have a 264 win mag ruger 77 rifles which have the weird throat for the factory loads .I also have 260 rem savage model 11 rifles which shoot the heck out of lapula 155 grain mega tip bullets clover leafs at 100 yards but that's a 300 yards bullet out of the 260 rem and 400 yards out of the 264 win mag .I was wanting to know if there is a bullet which would hold up good close and long range say 500 yards .I have only used the lapua bullets in both rifles but it's .377 bc is not good enough for longer range .I want to shoot further for wide open shots no brush .I have used the 260 alot more than the 264 lately the 260 is almost 3 pounds lighter .I am becoming a big 260 fan quick .I also have an ar10 260 rem that's super accurate .

What's the twist rate?

You never said what you are shooting but if it is deer size game here is what I chose for the 264 Win mag that holds together at 25 yards but still expands and kills the same out to about 550 yards so far. Because my rifle has a 9 twist I chose the 130 Gr Nosler Accubond. Very accurate and fast with Retumbo. I have killed a couple dozen plus with this combo and all have been DRT. The Accubond flies like the ballistic tip and starts to open up like it but holds together like the partition and keeps on penetrating. Out of my 27 3/4" barrel doing 3350 fps average it shoots like a laser beam over the bean fields.

I would suggest a 130gn something. Not too heavy for a standard .260 and not too light for the .264WinMag.
The 130 AB, 129 ABLR, 130 TGK, 130 Berger VLDH, or 130 Scirocco. All of these have decent BC's for LR and should do well in either cartridge.