What Actually Changes When You Switch Calibers

People new to progressive presses tend to assume a caliber conversion is a bigger job than it is. It is four components, a toolhead, and about ten minutes once you have done it twice. What matters is understanding which parts contact the case, because those are the parts that cause problems when a round does not come out right.

The four parts that change

Every Dillon conversion kit contains the same four items. They are the only pieces that are caliber specific on the machine itself.

• Shellplate. Holds the case by the rim as it indexes around the toolhead. Wrong shellplate means the case sits at the wrong height or does not hold at all.
• Powder funnel. Drops through the case mouth and flares it slightly so the bullet starts straight. This is the part people most often forget to swap.
• Locator buttons. Three small spring-loaded pins that keep the case square in the shellplate at each station.
• Casefeed adapter. Sizes the drop tube to the case body so rounds arrive one at a time, right way up.

The dies are not part of the conversion kit. Dies live in the toolhead, and the toolhead comes off as one assembly with the dies still set. That is the whole reason to buy a spare toolhead per caliber.

What stays put

The frame, the primer system, the powder measure body, and the crank are not caliber specific. The primer system does change between small and large primer, but that is a size change rather than a caliber change, and it is a separate part from the conversion kit.

Small primer or large primer

This trips people up more than caliber does. A 9mm and a .45 ACP both use small and large primers respectively, so moving between them means changing the primer punch, the primer seating cup, and the magazine tube. Budget a few extra minutes the first time.

The order that saves time

1. Pull the toolhead with the dies still in it. Set it aside as one unit.
2. Remove the shellplate bolt and lift the shellplate off.
3. Pop the three locator buttons out. They are spring loaded, so cup your hand.
4. Swap the powder funnel inside the powder measure.
5. Change the casefeed adapter at the base of the drop tube.
6. Reverse the process with the new caliber parts, then set shellplate bolt tension so the plate turns freely with no vertical play.

Shellplate bolt tension is the single most common cause of powder spill and inconsistent primer seating. Too tight and the plate binds. Too loose and cases rock at the exact moment powder drops. Snug it, then back it off until the plate rotates with light thumb pressure.

How long it should take

If your first conversion takes an hour, that is normal. The second one will take half that. By the fourth you will stop reading the manual.

Before you load

Run five cases through with no powder and no primers. You are checking that the case indexes cleanly, the funnel flares the mouth without shaving brass, and the finished round drops free of the shellplate. Measure the overall length on all five. If they vary by more than a few thousandths, your seating die needs adjusting, not your conversion.