Well, I'd start off with a good cleaning of the barrel. Maybe some JB Bore Bright if you have alot of copper build up.
Then, I'd put the Hogue grips on as Laddy Smith suggests. They make getting a good grip on the 457 a whole nother ballgame.
Finally, I would gather a selection of different manufacturers rounds and try 185 grain rounds in addition to the 230 grain 45's. Every S&W 45 I've shot is a "law unto itself". They all exhibit varying degrees of accuracy, from "tack driver" to "meh" and a "preference" if you will, for specific ammunition.
My 4513TSW's and Shorty45 MKII which are closely related to your 457, all prefer Winchester Ranger 230 grain JHP's. They are most accurate with these rounds.
Then there is the practicing.
I don't know your level of familiarity with the compact 45, but you need to practice a bit and regularly to get to where you can put those tiny "gun writer groups" on paper. Good luck! Hope this helps! Regards 18DAI
Edited to ad: Thats a 3 inch Shoot-N-See target with a one hole group of 7 rounds of Ranger 230 grain RA45 out of my off duty 4513TSW. Good ammunition.