Drop-in still may need to be fitted.
First, make sure the trigger bow is the same length as the one coming out (that takes care of sear/disconnector).
Second, most aftermarket triggers require some filing on the trigger pad. This is the time and patience issue. Use the file and for every swipe on the top, swipe one on the bottom.
Trial fitting as you go is the rule.
It should "drop" when the frame is pointed nose down.
Check that the trigger bow does not interfere with a magazine. That will increase the trigger pull.
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