A sticky Rear Takedown Pin

I have found the Rear Takedown Pin (RTP) on my new AR15 lower receiver to be a bit hard to engage and disengage. It seemed to “stick” at either the fully engaged or fully disengaged positions. One day recently, I disengaged the RTP and removed the upper receiver. When I tried to push the RTP back into the detached lower receiver, it would not budge. Hmmmm.

The RTP has a slot along its shaft. A small spring loaded retainer pin that keeps the RTP from coming completely out of the lower receiver rides in the slot. At either end of the slot there is a small shallow hole with a smaller diameter than the retainer pin. The slightly rounded end of the retainer pin conveniently helps hold the Takedown Pin in position when in contact with the holes.



I removed the stock to retrieve the retainer pin spring and the retainer pin itself. I found that the retainer pin had a stub at the end instead of a smooth rounded surface (see photo). It was almost like the pin came on a “tree” (think how plastic model parts come) and each one is snapped off the tree before its installed. This may not be the case; it just describes what the abnormality looked like.



I used my Dremel tool to grind off the “tree stub”. Then I put the pin in the Dremel to spin it against a fine polishing stone to smooth a slightly rounded end on the pin. Once satisfied, I reinstalled the Retaining Pin and found that the takedown pin no longer stuck at the ends of its travel. Whalla!