Checkout item# 714015807 and you can use both of them. There is no weatherby 6.5 creedmoor. But you can use Hornady 6.5 creedmoor.

The 6.5-300 Weatherby is the 300 Weatherby necked down to 6.5 and will not interchange with the 6.5 Creedmoor which is much smaller. The Vanguard rifle you want will accept 6.5 Creedmoor ammo only. 6.5 Creedmoor Ammo is readily available from several manufacturers.
budsgunshop.com/catalog/product_info.php/products_id/1014/Hornady+Precision+Hunter+6.5+Creedmoor+143gr+ELD-X />budsgunshop.com/catalog/product_info.php/products_id/22374/WIN+DEER+SEASON+XP+6.5CREED+125GR+POLY+TIP />budsgunshop.com/catalog/product_info.php/products_id/712014670/Federal+Trophy+Copper+6.5+Creedmoor+120gr+20rd

Buds Item #714015807 is Weatherby's Magnum version of the 6.5 Creedmoore. NEVER HAS A 6.5MM BULLET GONE FASTER!
In 2016, Weatherby ushered in a new era in ballistic superiority by introducing both a new cartridge and a new caliber of bullet to the Weatherby line.
The 6.5-300 Weatherby Magnum is the fastest production 6.5mm there is. Combined with high Ballistic Coefficient (BC) projectiles designed for long range shooting, the velocity of the 6.5-300 Weatherby Magnum opens a whole new world of possibilities and provides hunters with the terminal performance every Weatherby shooter is accustomed to.
Weatherby; once again proving that nothing shoots flatter, hits harder, or is more accurate; now in 6.5-300 Weatherby Magnum.

Jaymin, you can use any SAAMI Standard 6.5 Creedmore ammunition in this rifle of any Factory Ammunition Manufacturer.