The adjustable OEM triggers in the Vanguard are not the best and I actually could not adjust the trigger down below 4 lbs. in mine. I got a Timney when Midway USA had them on sale and all problems went away.
The weight of pull you may want depends on how you plan on using the gun. I carry my rifles in the field in Wisconsin during the firearms deer season in late November and my hunting area is 100 miles North of Green Bay. Temps can range from +60F to -25F. In view of that, I don't like anything lighter than 3 1/4 lbs. If you shoot from a blind or bench in warm weather, you can and probably will want to go lower.
Bruce