takedown pin on AR-15

My receiver is missing the detent spring. How hard is it to replace?

Not a big deal at all. Go on YouTube and watch a few videos on it. Until I bought a special tool to do it I just used a punch and pushed the punch out with the takedown pin.

Everywhere I can, I add set screws to keep those springs in there.

I've seen that mod. Doesn't look too hard. Seems I just need lo loosen the castle nut and rotate the backing plate.

Just a little tap action and a set screw. Also under the grip and bolt release.

Sorry guys I was thinking the front take down pin. The rear is even easier. That's a good idea on the set screw for the rear.

So to be clear, you setscrew the pin and don't use the spring?

No you clip the spring about the length of your set screw and tap the reciever and insert the detent then spring then screw in the set screw till it is just under flush of the back of the reciever.

OK, that makes perfect sense, thanks!

That's typically referred to as the "pivot pin".