Which .264 cartridge

[Mike D Texas]

Mag bolt face guys...
That leaves 6.5CM, .260 Rem, 6.5SLR, .260AI out of the equation unless you get a new bolt.
If it was a standard bolt face the OP had, I would definitely get behind the 6.5SLR bandwagon. Love mine.

Out of the OP's selection, of course I have to say 6.5SS in a true short action. I just picked up my 4th last week.
My 20" 1:7.5" 6.5SS can push a 156 @ 3001fps, but I have since backed it down to 2920fps. Or a 140 @ nearly 3100. Or a 129 AH @ 3300+.
View attachment 295086

I missed the mag bolt face part.

I would do a 6.5 SAUM.

 

[SteelBanger]

The PRC is the obvious choice for anyone needing factory ammo, but since you reload it makes the Sherman SS the only choice in my book. I have a 7SST and love it, planning to put a 25 and 6.5 Sherman in the safe as well!

 

[AZ Patriot 17]

6.5-300

 

[AZ Patriot 17]

Just saw the bolt face post. Disregard.

 

[Salmonhead]

6.5 PRC if you can get 2.955 in your magazine.
6.5 SAUM
6.5 WSM
Or the Sherman offerings

All launch good bullets at reasonable velocities to do what you need doing