I had a pair of Rem 513 target rifles, and now have a Rem 510.
There isn't a whole lot you can do with that trigger as its design doesn't allow for it.
One major issue with it is the sear acts as a bolt stop, and if you open the bolt a pull it hard to the rear, the sear edge gets all buggered up. So, open the bolt gently. That edge that gets deformed is the edge that releases the trigger; a dumb design.
I took all of the triggers apart on these rifles and replaced parts that needed replacing. Gunparts.com carries replacement parts. If you look at the bottom of the rifle, you'll see a Belleville type spring with two screws, one at either end of the flat spring.
Here is the "school" info on these two screws:
"Trigger Pull - Overtravel is controlled by adjusting trigger cushion spring attached to receiver at bottom, forward of trigger (see Sectional View). Remove stock by loosening takedown screw. With rifle in fired condition (bolt uncocked), tighten rear trigger cushion spring adjusting screw. Turn until screw just touches trigger. Then when trigger is fired rear screw will limit overtravel as trigger is pulled.
Weight of Pull - Adjusted by turning front trigger cushion spring adjusting screw. Tighten or turn inward for heavier pull. To lighten or reduce pull weight, turn front screw outward or counter-clockwise."
I got most all of my 500 series triggers to pull about 3-4 pounds. One I got all the way down to 2 pounds, but I think that was a fluke. I had a Rem 521 also that I gave to my grand daughters to use, and that trigger is the same as all of the o6ther 500 triggers, except for the Rem 514, which is a different design.
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