Using a small rifle primer in pistol ammunition is generally not recommended. Here are some important points to consider:

### Differences in Design
1. *Primer Composition*: Small rifle primers typically have a harder cup than small pistol primers, designed to withstand higher pressures associated with rifle cartridges. This can lead to inconsistent ignition in lower pressure pistol cartridges.

2. *Sensitivity*: Pistol primers are usually designed to be more sensitive to ensure reliable ignition in firearms that operate at lower pressures.

### Potential Issues
- *Misfires*: Using a small rifle primer may result in misfires or failures to ignite due to the increased hardness.
- *Pressure Concerns*: A softer primer can cause the primer pocket to expand, which can lead to potential safety issues.

### Recommendations
- *Stick to Manufacturer Guidelines*: Always follow the manufacturer's specifications for your specific ammunition. Use the primer size and type federal 205m primers that is recommended for the caliber.
- *Consult Reloading Manuals*: These resources provide valuable insights into compatibility and performance, ensuring you choose the right primer for your application.

### Conclusion
In summary, while it may be possible to use a small rifle primer in some pistol rounds, it is not advisable due to potential reliability and safety issues. Always prioritize using the appropriate primer type for optimal performance and safety.