I wonder how this would work, if you tried to put one in a soft plastic worm.

they sell glass ones with a pointed tip that you can just push into any soft plastic bait.

Keeping them in position while injecting the plastisol is the problem. Then, if they get over on one side, they just fall out of the worm.

Yeah. I figured it would need to be a different type of mold. I was thinking about the laminate worms, but those are injected too. I forget who made them, but people have made worms with some kind of air pocket in them. It was one of the big names.

Depends on if they are heat resistant at 300-350 degrees.

It can be done in a hand pour and it can only be done in certain configurations and is a time consuming process. ie. a 5' stick, the placement has to be such that it doesn't interfere with the hook in a Trig, there's also the issue of balance by virtue of adding weight to a bait that is reliant on it's action. Salt impregnated baits with an already existing durability issue adding the rattle makes it even less durable. Lastly, plastic rattles have a different sound than glass, you can use plastic as long as you don't overheat the material however the plastic rattles with a more muffled sound is muffled even more when surrounded by plastic.

They make rattles that insert into plastic specifically for this.