Shoot and load for .223/.243. Have switch barrel model 16 but hate to change the bolt head/baffle.

Is 6 x 45 factory loaded ammo available? If so, that may be the 6x45 caliber works ok for medium sized deer as an in-between caliber .223/.243 without changing the bolt assembly. Can read ballistics charts, but anybody shooting these three for comparison? Never shoot live game over 250 yrds.