After manipulating the pix a bit with software . . . .

Headstamp is:
"| T (symbol) C |" at 12 o'clock.
"7.9 | F.S. | 1960" running from 3 to 9 o'clock.

According my one reference listing a "F.S." maker, these intials are found on 7.92x57 ammo made at Solothurn, Switzerland. Given the headstamp, profile and case length I would lean toward it being a 7.92x57 (or posssssibly the 7.9) and the full bullet diameter is on the shank below the case mouth or (sorry, but it must be said) there was an error in measurement.

All of my references lists the 7.9x57J as using a .318 dia.
bullet.None of the 65, 7.9-8mm, cartridges listed in my references use a bullet smaller than .316 dia.

WC

you guys this one is simple, just plain ole turk surplus 8mm. usually shoots great out of a 98/22 or vz24

Yep, FS means FMJ.