Grant finished with a game-high four goals and 24 possessions in the club's 28-point win over Carlton at Etihad Stadium on Saturday.
Watch Jarrad Grant's four goals on BulldogsTV.
After struggling to break into the senior side this season, Grant has now kicked 12 goals from his five games in 2013.
McCartney believes the forward, who was selected at pick 5 in the 2007 NAB AFL Draft, is starting to reach his potential.
"He's quite exhilarating to watch," McCartney said on Saturday.
"We're just really happy for Granty. The number one thing, the way he's playing is a by-product of him growing up and accepting that when he's out on the field in a Western Bulldogs' jumper, you play a certain way.
"It's just terrific to see how hard he's attacking the ball and believing in himself.
McCartney admits coaching Grant hasn't always been smooth sailing.
"I think we've had an interesting 18 months, Granty and I," McCartney said.
"I've got no doubt that this 12 months, and in particular, the last few months, the respect levels are very high, coach to player and player to coach. That's helped.
"We've had our good days and we've had our not so good days, coach to player, but he's coming out the other side. "
Grant's teammate Tom Campbell said the playing group was thrilled to see the forward playing a high standard of football.
"I've played a lot of footy with him in the VFL this year, and behind the scenes he's done a lot of work," Campbell told AFL.com.au.
"It's really great to see that Jarrad is played some good footy towards the end of the year, and I know that he's going to be a really good player for us for a long time."
Jacqui Reed is a reporter with AFL Media. Follow her on Twitter @JacquiReedAFL
