Before you rush out to shoot it, double check the auto sear release timing (to all the upper you will be running on the lower).


Insert drill bits (back side) between the face of the carrier and the back of the barrel extension port with the trigger held back, the charging handle rod down, and the selector in full auto.

The release gap you are looking for is in the range of .082", which would the hammer not releasing with say a 3/32" drill bit (.0937), but will release when a 5/64(.0785) drill bit is put in place.

If you find that the sear release gap is too advanced (hammer will release off the sear with the 3/32" drill bit, then its the tab on the auto sear that you want to work to correct the timing (back side where the bottom carrier tab contacts it).  If you have to do this, then a #47 (.0785) is your go drill bit, and a #44 (.086) drill bit is you no go gauge.

Simply, with the gap at .082, the rifle will pur along nicely.  At a larger gap, it increases the cycle rate, and if too advanced (+.100), you get into the range where the hammer can come down on the back of the FP before the bolt has had a chance to close (not a bolt bounce thing, since the hammer came down even before lock up happened).   As for less than .082, then you can get into wicked bolt bounce since the bolt has fully locked up well before the hammer is even released, and the carrier has too much time to begin bolt bounce if the buffer is not controlling it.

Side note: with a good buffer, you can decrease the release gap to slightly slow the rifle cycle rate down without fear of bolt bounce.  Is it advised, not really, since it easy to leave the release timing alone, and use a heavy buffer to not only slow the actual B/C movement down, but to lengthen the dead blow effect as well to slow the fire rate.