Trouble with AR-15 take-down pin

[Nick5182]

I've got a DPMS AR-15 complete lower. The pivot pin on the receiver goes in and out just fine and the detent locks secure. The Rear take-down pin, though, will go out just fine, but once it's locked in the most outward position, I can get the pin to go back into the receiver. I'd hate to have to unscrew the castle nut everytime I wanted to take down this rifle, once I get an upper. Does anyone know why it does this, or how to remedy it? Any help will be appreciated.

 

[TRguy]

If it is a new lower or newly install LPK then many times the detents are hard to get in and out of the detent hole.

I would try lightly taping with a non marking hammer to get the detent to break loose. Then repeat that about 10 times until it breaks free easier.

You can always cut about two or three rounds off the detent spring so there isn't so much pressure. I would start at two rounds and go from there. You can alway cut more, can never add back.

Try the mallet first and see if that loosens it up some.

 

[ny32182]

I'll mostly second what TR said; first thing to do is shoot it... the pins tend to loosen up considerably after 2-500 rounds down range. Till then I'd tap it with a mallet. If it doesn't loosen up after that I would look at either cutting the spring, or replacing the detent and/or pin... There could be a chance you have an extra deep recess in the pin where the detent goes for some reason.

You should not be unscrewing the castle nut on a regular basis. In fact, on a 100% properly built lower, the endplate will be staked into the castle nut to prevent it from rotating; since this displaces metal a new endplate would ideally be used when reinstalling any time the castle nut is removed.

 

[P-32]

I have 2 AR's Both with White Oak Precision uppers and both have RRA lowers. On one riffle the back push pin is no problem, the other almost needs a vice to squeze the upper and lower together to get the rear pin in.

 

[NG VI]

Use your index or middle finger knuckle and give it a strong rap, one that doesn't feel good to you.

That's what I always did in Basic, but my CMMG was easier to get apart than the somewhat raggedy FN I was issued there. Can't remember about the different Guard rifles I've used, don't remember them giving me any toruble.

If that doesn't work, non-marking hammer, rubber mallet, something along those lines should do the trick.