Noob AR part question... no doesn't have to do with slidefire...

[Rogue9517]

What's that diagonal bar connecting the 2 pins above the trigger?

I haven't seen them in any AR pics on this forum (I don't think) but I see them on a lot of AR's on AR-15.com.

Something to do with full auto for the states?

 

[justinchow]

They're anti rotation pins. You can get them from Brownell's and sometimes from One Shot

 

[hbean]

They prevent the pins from walking out, generally it is not necessary unless your lower has really loose tolerances or has high mileage.

 

[blaxsun]

KNS anti-rotation pins. There are two types: the skinnier (gen 2) version which works on all standard AR lowers and the fatter (gen 3) version which is designed for ambidextrous lowers with a right-hand bolt release (KAC, POF and others).

 

[Armedsask]

They are useless on 99% of civilian AR15's. They are mostly a Kool-aid item.

Unless you are rocking full-auto reguarly, pretty pointless.

 

[P0WERWAGON]

or a 9mm AR could use it.