SharpsNitro you are spot on there. As per below its a beast.

High velocity 6.5 mm

Among the wildcat versions of the .338 Lapua Magnum, the 6.5-338 Lapua remains possible the as the fastest. Originally designed in Finland, it has to be one of the highest velocity cartridges in this bore size.

The 6.5-338 is necked down from the .338 Lapua Magnum case to the 6.5 mm (.264 caliber) bullet. The shoulders are pushed back somewhat, and the body taper is reduced by fireforming. In its finished form, the case body is almost cylindrical. The final case capacity is slightly greater than that of the parent 338 Lapua Magnum.

Ballistic performance is impressive, to say the least! With top loads, a 9 g (139 grs) Scenar HPBT bullet will leave muzzle at an incredible 1150 mps (3780 fps). By comparison, the 6.5-284 will shoot that same bullet with about 930 mps (3050 fps) muzzle velocity.