Grease groove angles   There's more than one way to measure the groove angle.   The picture shows how I measure it, just so we're on the same page.   55° is about as steep as I care to go, any steeper and you're inviting difficult release from the mold.   The steeper angle does hold a little more grease so it may get the nod for blackpowder bullets and original Keith bullets.   A 45° angle offers slightly better release and is a good choice for most other applications.