Odd AR trigger bug

[yellowfin]

Today was a great day to get out to the range and enjoy the beginning of spring. It was only the 2nd time out for my new pet, and it shot flawlessly except for one bizarre instance I wonder if you guys could explain. About midway through the 2nd mag and somewhere once in the 3rd it fired when I reset the trigger, like just when it clicked without any significant travel. It's just a regular stock trigger with a measured 4.375 lb pull, totally unaltered and nothing fancy about it. Is there anything in particular that could cause this and is it something to fix now or will fix itself generally? Maybe I oiled it too much? I gave the bolt a fresh blast of CLP last night before shooting this afternoon.

[yellowfin]

Anyone, anyone at all? I'm taking a few people shooting for the first time soon so I need this to be working right so it doesn't scare them.

[chaoticmind]

Check the dis-connector.

Check the dis-connector. Make sure the spring is not in upside down. Make sure there is no excessive wear where the dis-connector catches the hammer.

[yellowfin]

Which side is right side up for the spring?

[damndave]

I used this guide (with pictures) on my 1st build. Common issue to have a spring upside down.

http://www.ar15.com/content/guides/assembly/lower/

[dfletcher]

Which side is right side up for the spring?

Like a pyramid - wider at the bottom than at the top. If the disconnector spring is straight all the way up, that's the bolt hold open spring. Common mistake.

[yellowfin]

Aha! You were right, the spring was upside down from what you're describing. I put it back right side up (and it DID NOT want to cooperate at first--VERY skinny hole EXACTLY the right size) and dry fired a couple times to check to see if it was behaving properly, and it is so far. I'll take it to the range this afternoon to see how it does. Good thing is I knew how to do it from having built it myself. Thank you so much! I'll post an update later.