I built my first 6x45 some 30 years ago. I still have that rifle and have shot a lot of game with it. I have culled Kudu, Springbok, Hartebeest, and Impala with it. I have shot Mule deer, Pronghorn, Rockchucks, coyotes and other varmints. All one shot kills btw and thats a better record than my .416 Rem I think!
I use only two bullets for big game, the 75 gr. Barnes X no longer available but I still have a small supply and my all time favorite bullet is Gerards GS Customs 75 gr. Monolithic Hollow Point. Both will out penetrate or at least equal any 100 gr. bullet.
For varmints I like the light Nosler Bal. tips and the great 60 gr. Sierra HP..
My rifle is a Sako L-461 with a 3 pos. mod. 70 type safety that Tony Barnes built out of a piece of bull barrel. A Douglas barrel, and a 0 tolerance bench rest chamber. It is stocke in dark red full fiddle back claro that Tony had and took 28 LPI checkering, I have never seen a piece of claro that hard or as Jack Belk said, that piece of wood is "harder than Woodpecker Lips" Barrel is 18 inches and the gun looks like an old English big bore..I shot a couple of 10 shot groups with it that mic .265 and .510, not too shabby..Its the most accurate rifle I have ever owned, thus the 30 years without selling it.
Great gun and great caliber.