What is a major consideration when beginning to prime?

Using the primer brand and size specified for the load is crucial because primers are designed to ignite the propellant in a cartridge effectively. Each primer type varies in sensitivity, dimensions, and cup thickness, impacting ignition and overall performance. Selecting the correct primer ensures that it matches the case, powder type, and intended bullet load, which helps achieve consistent pressures and velocities for reliable firearm operation.

Additionally, using an incorrect primer could lead to either insufficient ignition or an over-pressured situation, potentially causing malfunctions or safety hazards. This principle aligns with the essential practices in ammunition loading, emphasizing the importance of compatibility in components.

While ensuring primers are fully seated is also a key safety consideration in the loading process, it is secondary to the importance of using the correct primer brand and size, as improper primer selection can lead to foundational issues in the cartridge's performance.