I have to disagree. The spring for my rear takedown pin detent DID shoot across the room. Luckily I found it.
1) remove the buffer/buffer spring.
2) loosen the retaining ring and SLOWLY slide the retainingg plate so as the Takdown Pin detent spring doesn't get lost.
3) slowly unscrew the buffer tube. BECAREFUL! the Buffer retainer is being held down by the Buffer Tube. I usually cup my hand over the lower reciever to keep the Buffer Retainer from getting lost.
And Viola, you're done.
To reassemble just reverse. Of course when you are putting back the buffer tube, you'll have top hold the Buffer Retainer down until the tube covers it enough. When the Tune cannot turn anymore turn the tube back out until it's aligned the right way. I've found it helpful when screwing in the retaining ring to push the retaing plate upwards so the little tab is upagainst the tube (you'll see that channel on the botton threads of the buffer tube)When I didn't hold the plate up the retaining ring always came loose.