With the little experience I have at pouring, I quickly noticed that, as an example, a 1/8 ball collared jig head with a #2 hook will run close to actual weight. A 1/8 round jig head without collar will run about 25% less. Same trend seems to hold for 1/32 and 1/16.

Also noticed some sinker manufactureres no longer go by weight , but "size". #7, #4, #3, etc...

The few people I have had comment about wieght descepency, I have just told them the head is the same size as a collared jig of that weight.

All have been OK with that.