Can a tear drop forward assist fit into any A4 upper receiver (flat top)?

It will fit in the upper fine.

I may be totally wrong on this, but wasn't the switch from teardrop to round due to some sort of interference with the takedown pin reinforcement on the A2 lower?

i don't care for either they get in my way, i have never even had to use one even  while i was in the Marines.


Dang i sounded just like all these people who bash every thing said on a post, sorry

Tear drop will swap for the round, no problem.  And no, it won't interfere with the receiver reinforcement.  

The switch was made from tear drop to round because the round FA is easier to make and less prone to snag on clothing and equipment compared to the TD shape. The round FA is made on a screw machine as opposed to the cast TD FA which is not as strong as a machined part.   PATRIOT ARMORY 07 FFL

For my first build I used a LMT upper, and the Bushy teardrop I ordered did NOT fit.  

I have also heard that the TD FA is more prone to breakage than the round, but I prefer the extra surface area of the Teardrop.

The tear drop has more surface to contact should you use it but either work fine. The serations on the tear drop assist in getting good contact with the FA but I have had the tear drop catch on gear, vegitation etc.

We in the Army teach the use of the forward assist as part of an immediate action drill if the rifle fails to fire. Do you guys remember SPORTS?

Slap - the bottom of the mag
Pull - the charging handle to the rear
Observe - the chamber for a round or the ejection of a round
Release - the charging handle
TAP - THE FORWARD ASSIST
Squeeze - the trigger