Stone shrinks when it locks
Loose stone settles 15–20% as angular pieces interlock under compaction and traffic. A 4" goal needs ~4.7" loose — the tonnage calculator adds the factor, and forgetting it is why "I ordered 4 inches" driveways end up 2.5. The shrinkage is physics, not delivery error.
Lifts, not layers
Compaction reaches only ~2" deep per pass: a 6" base compacted once is dense on top, loose underneath, and settles unevenly through year one. Two or three 2" lifts, each compacted, build uniform density — the entire secret of surfaces that stay graded. The plate compactor ($60/day) is the best rental in landscaping.
Moisture is the helper
Slightly damp stone compacts dramatically better than bone-dry or saturated — the fines need moisture to slide and lock. Sprinkling each lift before compaction is standard practice; the "wet sandcastle" principle scales up to driveways. Crusher run's fines make it the most moisture-responsive (and most compactable) of the family.