The .243 Winchester round in general is 6mm perfection at its best without being overbore. Any round based on the .308 case is sure to be efficient with the exception of the 22/243 (silly idea, just by a swift). Its a proven long range varmint slayer and with a adaquate bullet very effective on deer. I have 3 rifles chambered in .243, one being a Handi and love them all. What I have found with my .243 ultra is she likes 75 grain V-max bullets the best pushed by 39.5 grains of IMR 4064, not maxed by no means but rite in the sweat spot for my bore, I would share seat depth but your bore is not mine. If I could change anything about my Ultra it would be a faster twist rate as 100 grain soft points and my bore are not on speaking terms regardless of velocity. I have yet to see a .243 barrel shot out so one would assume a lifetime of shooting pleasure to be had. If you never owned a .243 before you will be pleased with its performance for sure. Let us know how you make out at the range.