I believe Timney makes a trigger for the ATR.
To see whether the trigger you have can be adjusted, I'd have to see the trigger. Can you shoot us a couple of pictures of the front and back of the trigger mechanism from an angle?
In the end though, you'll probably have to go for the Timney trigger if you want it to be really outstanding. I think they cost around a hundred bucks, something like that.
Kind regards, charlesb