Sakoluvr,
The difference isn't in how Hornady's making their Interlocks--they're still making them the same way as always.
Instead I suspect the difference is due to the wider amount of exposed lead in the roundnose, which tends to make them expand more even at moderate velocities. The Spire Points have far less lead exposed.
Have heard of the same erratic performance in other Interlock roundnoses, and even experienced myself once with their 150 RN Interlock in the .30-30.
