25-06 is a great blacktail round. Most 100-120gr bullets work fine on blacktail. Shoot what your rifle is accurate with.
My buddy has done well with CoreLokt ammo in his 25-06 on blacktails for 30 years. I preferred Nosler 110gr Accubond. But the Federal ammo is half the price of the Nosler (and even less than CoreLokt), and should work just fine. Federal manufactures some good variety of 25-06 ammo with Speer, Sierra, Nosler, etc. bullet options. And Hornady has their lower cost Whitetail brand as well in 117 interlock SP that should get the job done.