fails to"fire"

[Thor]

Is there any wear on the side of the receiver next just in front of the sideplate. Can you hear the disconnector reset with a "click" when you release the trigger after the action is cycled manually? If you see wear on the receiver and the action doesnt click to reset, the trigger lever is probably over rotating preventing the reset. This wear mark is normally from the trigger lever dragging on the receiver during the recoil cycle.Take the top section off and put the side plate back on the frame and see if the trigger lever rotates beyond being flush with the edge of the trigger plate when the trigger is fully pulled. Most of the time this is the cause in trigger reset failures.
Here is an example of the lever drag mark. Some folks think it is sideplate dragging but most are not the sideplate but the trigger lever.
<a href="http://members.rennlist.com/lugerman/HC1900AEB2.JPG" target="_fullview"><img src="http://members.rennlist.com/lugerman/HC1900AEB2.JPG" width="400" alt="Click for fullsize image" /></a>