The term “cam over” can sometimes lead to confusion when discussing reloading presses, particularly models like the Rcbs Rock Chucker. In a recent discussion, a user, Mr. Guffey, raised a pertinent question about the definition of “cam over” and its implications for the functionality of his Rock Chucker press. It’s important to clarify what “cam over” means in this context and address the potential variations in manufacturing that might influence press operation.
When we talk about “cam over” in presses like the RCBS Rock Chucker and RCBS Jr. II, it generally refers to a design feature where the ram reaches its maximum upward travel slightly before the press handle reaches its absolute lowest point. As the handle is fully lowered, the ram may actually descend very slightly from its peak position. Mr. Guffey describes this phenomenon as the ram reaching its maximum height “at about 5º shy of full handle travel and actually falls downward slightly when the handle is fully lowered.” This description aligns with the common understanding of “cam over.”
The purpose of this “cam over” is not always immediately obvious, but it’s a deliberate design choice. One practical implication, as Mr. Guffey points out, relates to primer seating. If a user adjusts a die to stop the ram at its absolute maximum travel, it might interfere with the operation of a press-mounted primer seating attachment. Specifically, there might not be enough clearance for the primer cup to clear the shell holder before the depriming pin contacts the newly seated primer. However, it’s also noted that in such a scenario, the ram may not actually “cam over” in the traditional sense.
Mr. Guffey also astutely brings up the concept of “stack up” in manufacturing. This is a well-known principle where variations within acceptable tolerances of individual components can accumulate, leading to overall variations in the final product. Even in relatively simple devices like reloading presses, manufacturing tolerances exist. It’s entirely plausible that some RCBS Rock Chucker presses might exhibit slightly different ram travel characteristics due to this “stack up” effect. One press might represent a minimal tolerance build, while another could be closer to the maximum tolerance, resulting in minor differences in “cam over” behavior. This variance is a normal aspect of manufacturing processes, even for precision equipment.
Finally, it’s worth noting the point raised about ram or press body wear. RCBS guidelines reportedly indicate that any play or movement in the ram, either forward, backward, or side-to-side, could suggest wear in the ram or press body itself. In such cases, replacement or bushing might be necessary to maintain optimal press performance and reloading precision.
Understanding “cam over” in your RCBS Rock Chucker is essential for consistent and safe reloading. Recognizing the potential for manufacturing variations and being aware of signs of wear will help ensure your press operates as intended for years to come.
