How do keep auto-correct from making one particular change
Add a text replacement for srs to srs. This appears to preempt autocomplete from changing it. The technique is the similar to this answer for how to choose the correction to a typo.

To suppress a specific auto-correction:


Open System Preferences
Open Keyboard
Choose the Text tab.
Click the + below the replacement list.
Add the same word to the Replace and With columns
Close System Preferences.