Thank you larry1096 for the more in depth explanation. I didn't mention it but the check was with the trigger pulled very hard. So, if I got this right, the thumb safety is allowing the sear to move a certain amount when the trigger is pulled very hard, while it is engaged. Because the sear is no longer if full engagement with the hammer, it presents a percentage of danger in that the sear and hammer contact could slip once the thumb safety is turned off. Do I have it correctly or more easily if the trigger is pulled than normal?