How to Set Up Your RCBS Rock Chucker Supreme Press

You have the press on your bench, but the priming arm won't seat primers or the mount feels unstable. This guide walks you through the exact steps to install the priming arm, secure the frame, and calibrate your dies for consistent ammo.

What you need before you start

Gather these items before you begin mounting the press. Missing hardware delays setup and compromises stability. Having everything within arm’s reach prevents the frustration of stopping mid-installation to search for a specific washer or oil. Before you buy anything, it is worth looking at understanding the drop mechanism.

• Bench: Solid wood or laminated top, at least 1.5 inches thick. Avoid particle board, which compresses under the heavy cast-iron frame.
• Hardware: Press bolts, large washers, lock nuts, and a drill with a pilot bit. Check if your bench requires longer bolts than included.
• Lubricant: Light machine oil or dedicated press lube. Avoid heavy grease on the ram surface.
• Tools: Wrenches for die lock rings, hex keys for primer arm set screws, and a clean rag.

If you are planning to swap to automatic priming later, have the tool ready now to test compatibility with your shellholders.

Mount the press securely to your bench

A wobbly press ruins accuracy and safety. Secure the frame before touching the ram or dies. The Rock Chucker generates significant leverage during the downstroke; any movement in the bench structure transfers directly into your case sizing and can stretch brass unevenly.

1. Position the press: Mark the mounting holes on your bench. Ensure the handle has full, unobstructed swing space to the side and back. Do not mount it near a wall that limits the handle travel.
2. Drill pilot holes: Use a bit slightly smaller than your bolts. Center them on the mounting holes. For thick benches, ensure the bolts are long enough to engage the wood properly.
3. Insert hardware: Place large washers under the head and washers under the bench side. This distributes the load and prevents the wood from crushing. Insert the bolts.
4. Tighten lock nuts: Use wrenches to secure the lock nuts firmly. Shake the press vigorously. There should be zero play. If it moves, your bench is not stout enough or the nuts are loose.

If your bench is thin, buy longer bolts from a hardware store. The goal is complete immobility. Check these bolts monthly as they can loosen over time due to vibration.

Lubricate the linkage and ram

Factory grease is heavy and sticky. Replace it with a thin coat of oil for smooth operation. This step reduces friction and prevents wear on the critical pivot points. A lubricated press cycles smoothly and lasts decades.

1. Wipe the ram: Remove excess factory grease from the ram and linkage pivot points. The ram might feel stiff initially; this is normal.
2. Apply light oil: Coat the linkage pivots where the handle connects. Lubricate the ram surface. Do not flood the mechanism; a thin film is sufficient.
3. Prep die threads: Lightly oil the press frame threads where the die lock ring will seat. This prevents the die from seizing.

Run the handle through its full range of motion several times. Feel for any sticking. If the motion is jerky, re-clean and re-oil. This initial care is a core part of your long-term maintenance routine. Before you buy anything, it is worth looking at using the correct mounting holes.

Install the priming arm and shellholder

This is where most setup errors happen. The priming arm must be fully seated to fire the primer correctly. The small metal arm snaps into the front of the ram. It uses a spring to hold the primer punch against the case head. If not installed correctly, primers will not seat or will seat unevenly.

1. Insert shellholder: Slide the correct size shellholder into the ram slot. Ensure it is fully seated. Secure it with the retaining pin. The pin must be flush so it does not catch on your hand.
2. Attach priming arm: Slide the priming arm assembly into the front slot of the ram. You will feel a distinct click when it locks into place. If it does not click, it is not seated.
3. Set primer punch: Insert the correct punch (large or small) from below. Tighten the set screw to hold it. Make sure the punch moves freely when you pull the lever.

Check that the spring tension feels firm. A loose arm will not apply enough pressure. Verify the punch aligns with the shellholder hole. Misalignment causes primer skewing.

Adjust dies for cam-over pressure

Die adjustment determines case consistency. Hand-tighten, then add slight pressure for full sizing. This step ensures the linkage passes center, applying full pressure. Incorrect adjustment leads to incomplete resizing or cracked cases.

1. Install resizing die: Screw the die into the press until it contacts the ram at the top of the stroke. Do not force it.
2. Cam over: With a case in the shellholder, run the ram up. Add one-quarter to one-half turn for resizing dies. This slight overlap ensures consistent pressure.
3. Lock the ring: Tighten the die lock ring to hold the position. Do not overtighten the ring, which can strip threads. Re-test the stroke to ensure it is smooth.

Repeat this process for bullet seating dies. Use a dummy case to test seating depth before loading live components. This dry run confirms your settings are correct.

Common mistakes that ruin setup

Even experienced loaders make these errors. Identify them early to save time and brass. We cover special 5 press in a guide of its own.

• Wrong primer punch: Mixing large and small punches causes seating failures. Check the punch size against your primer type. Mismatched punches can damage the primer or shellholder.
• Loose bench mount: A shaking press stretches cases unevenly. Re-tighten bolts immediately if you hear noise or feel wobble. The press must be static.
• Over-tightened dies: Forcing the die down crushes cases. Back off until the cam-over is smooth. Excessive pressure can crack brass or strip primer.
• Skipping lubrication: Dry linkage binds. Wipe and oil before your first test cycle. Friction generates heat and wears parts faster.
• Dirty primer slide: Debris in the arm slot prevents the click. Brush out the slot and ensure the spring is visible.

Fix these issues before loading powder and primer. They cause visible defects in finished ammo, such as bent primers or uneven bullet seating.

The bottom line

Frequently asked questions