Good point on the dust cover, M14, makes sense. Thanks!
And thanks for the info on Glock's trigger action yesterday. After our discussion yesterday I did more reading and people's opinions range from SA to DA to DAO. Glock just calls it "Safe Action" which is fine since with the slide and trigger each having a part in resetting the striker it sure blurs the distinction between SA and DA.
You're right of course that the Glock trigger technically does double action work by doing the final reset of the striker and then drops it - which probably falls into the range of DAO since this happens on each and every shot, not just the first one. But since the slide must be manually racked on the first shot to "half cock" the striker, and there is no double strike capability, the operation of the Glock is closer to single action.
Guess it's "1.5" action and you round up to 2 action while I round down to 1 action. You can argue something like you're rounding to the even number and I can say that single action and "safe" action both abbreviate to SA.