The argument has been raging for years. Cam over, is it good or bad. Do you use it and why would you? Cam over is a result of ths ram which is traveling upwards in a liner motion hits top dead center (TDC). At this point the linkage, which is traveling in a circular motion, can go past TDC and the ram will drop.

Not all presses are designed to cam over. Some are, the press that comes to mind is the RCBS Rockchucker. Presses like the Lee Classic Cast single stage does not have cam over built in. Is your press designed to cam over? To find out run your ram all the way up, screw in a die, then try to lower the ram. If you can not then your press is designed to cam over. The reason you can not lower the ram is because the ram is actually trying to go back up before it starts it’s downward trip.

To illustrate what cam over does, run a die into the press until the die contacts the shell holder. You should see no gap between the die and shell holder. Now place a cartridge into the shell holder and run it up into the die. You will likely see a gap between the shell holder and die body. Cam over is to ensure that the case will be forced entirely into the sizing die.

Most any die / press setup can be adjusted to act like a press with cam over, but be aware that this introduces tremendous stress into the press and may damage or break the press, especially if it is one of the less robust varieties.

To determine if you need cam over, you must first decide what you are going to do with the press. Are you going to swage bullets? Reform cases? If yes, then you likely need cam over. likewise if you are resizing brass that has been fired out of a machine guns, loading 50 BMG, or some of the larger magnum cartridges. If you are loading 9mm, 223, 308, 30-06 and the like you probably do not need cam over, Cam over and a properly machined and adjusted full length resizing die and shell holder assures that you will always set the resized cartridge case back to factory specifications.

But do you really want your cartridge cases resized to minimum specs? Are you loading for a semi-automatic rifle? Are you loading a cartridge that might be fired in multiple rifles? If the answer to these questions is yes, than you probably do. But if you are loading for an individual rifle you likely want to fit the case to your rifles chamber. This likely means that you probably will not be setting the cartridge case back to factory settings, but will be sizing the shoulder of your case to just a few thousands off your chamber. You do this by backing the die slightly out of your press. This act alone will remove the cam over from the press.

This raises another question. Some like their presses to cam over because they believe that it introduces consistency to the reloading process. Every action is controlled by the cam over action which puts the same pressure on the case every time. With a hard stop you are dependent on muscle memory to keep pressure consistent and thus repeatability can suffer. But what if you want cam over but having the press set up for it moves your case shoulders back too far? A set of competition shell holders will set your cases deeper into the shell holder allowing for more adjustability, allowing your cartridges to more closely fit your rifles chamber.

Personally, I believe that cam over stresses the press, especially the linkage. I do prefer a press with cam over when forming cases. I actually believe it’s almost a requirement. I also prefer cam over when full length resizing cases. For all other processes I prefer a hard stop.