The weight and springs do not set the amount of advance. They control how fast the advance curve is. If you look under the plate that the weights ride on you'll see two pins riding in their own oval shaped slot. The pins are attached to the piece in the center of the weights that the springs hook to. When these pins bottom out in the slot the advance has reached its' limit. The size of the slot varies by original application.
If this distributor is used or has set around awhile the fist thing to do is to remove the distributor and completely disassemble it for cleaning. The shaft and bushings are well know for becoming carboned up to the point that it can limit the advance or cause it to stick mid range of the advance curve. You get it apart by driving the pin out of the drive gear.
If everything is clean and you happen to have a distributor that was made with very little mech. advance you can file of grind the slots for more travel. Some times the little plastic bushings will break and get jambed in the works.