To answer the OP's question. The rifled (Forster) type slugs tend to weigh more than the Sabot type. Some of the slugs will weigh as much as 1 3/8 oz or about 600 gr.
Lighter slugs also mean you can get more velocity.
Yes you CAN shoot sabot slugs through a smooth bore. The problem will be that you may not/probably won't get any accuracy and most likely tumbling soon after exit of the barrel.