The Wallabies scrum were frequently outperformed by the British and Irish Lions during the summer, but the southern hemisphere pack have since played seven Tests under the new "crouch, bind set" law governing the engagement.
Some pundits have predicted Australia to struggle against England in the scrum at Twickenham on Saturday, but Horwill begs to differ.
"We've played under the new laws as a scrum, they're yet to play as a team under the new laws," Horwill said in a press conference.
Horwill feels that the Australia pack has "a better understanding of what's expected at scrum time and what we can do to get an outcome".
"We've learned in each game that has gone by, there's little thing that have given us the outcomes we want.
"There were some mental lapses in the scrum against New Zealand that let us down [in the third Bledisloe Cup Test]. We had some really good scrums and it was two or three that let us down, and that's not good enough. You need to be on your game in every single scrum."
England host Australia at Twickenham on Saturday.