This is old. It goes back to 1992, but if they knew the results here, it raises a question, why are we still equipping the Mk38s with 25mm guns instead of 30mm (or 35mm or 40mm) guns which also fit the same mount? The results are discussed beginning at time 8:00. The 30mm does nine times the damage to the hull and five times the damage inside the hull.
At the very least we need to make sure we have available rounds that do not detonate on impact. The 25mm rounds, exploding on impact, failed to even penetrate the 1/4 inch aluminum hull of the Mk3 target boat.
Thanks to Luke for bringing this to my attention.