At $2.00 per pound, lead shot can prove very expensive to fill four 25-pound bags. Instead try putting a large "zip-lock" inside the Caldwell bag and fill it with clean sand; it's not quite as heavy but will do the trick if you use all four bags.
Pros: Easy to handle, practical, fit their purpose exactly
Cons: None (Except that 100 pounds of lead shot is expensive!)
This review was written in the old system and had content requirements that are different than reviews written today.