30 carbine problem

[stone6kids]

I have a 30 carbine that functions perfectly on the bench, but in the field and on the range to trigger will not set and I have to push the trigger forward to set the sear. I can see for some reason the trigger will not fall and allow the sear to drop down except for fully assembled and dry fired, I have tried three types of ammo and two magazines to no avail. I have ordered a new trigger spring and cleaned the rifle thoroughly