I wanted to put down my thoughts,opinions and actions that I used to tune a CZ 550 in 458 win mag, from what I understand, that caliber is particularly difficult being short and fat. I searched the internet and there was not much to be found. Duane Wiebe has posted a brief process on another forum and Von Gruff posted Proper Magazine Layout on africahunting forum and these were most helpful but don’t really tell you why you do something or what it affects. I found that as you feed the round, things are more complex than you first think and changing one thing invariably changes another. For what it is worth, here are my thoughts, use them at your peril! Some of you may have more experience than me and can add some bits that I got wrong or left out.
The bullet riding up the ramp initiates the process the feed action so I started there. As it lifts the front of the round, the cartridge case contacts the feed lips/side rails and pushes the round away from the side of the magazine and towards the center to align with the chamber. I expected the ramp to funnel the bullet into the chamber but found the cone shape does little for the left/right movement. See the diagram below for more clarity.
I carefully removed a bit of the feed ramp to create a flatter cone shape and lower the feed angle slightly.
If you alter the angle of the feed ramp by making the angle shallower, the feeding round will move away from the rail later in the feeding cycle. In addition, if you remove the feed rail from where it touches the case as you feed, the round will also be pushed away from the rail less and later in the feeding cycle. I tried to keep the round feeding to the center of the chamber. I removed material from the feeding ramp to aim the cartridge just below center of the chamber. I figured that I was using dummy rounds with the shortest bullet or head(480 gr hornady dgs) Other heads would be monolithics or 500 gr solids and longer so I left room.
