I assembled a CAR kit and everything works fine, but my takedown pin will slide out under gravity - all I have to do is flip my rifle over.  My pivot pin, on the other hand, needs a wooden dowel and rubber mallet to push it open.

Did I get the springs mixed up or something (I don't think I did; the takedown pin spring looks too big to fit in the receiver hole for pivot pin spring.)

What gives???

The spring that goes behind the detent pin for the takedown pin is exactly the same size as the one for the front pivot pin detent.

Did you install the detent pin and the spring through the back of the receiver?  That detent spring is held in by the stock, see arrow in illustration below.

[img]http://www.pbase.com/image/24283453.jpg[/img]

That might be my problem; if I remember correctly they were different sizes (I thought.)

I did install the detent pin and spring through the back of the receiver.  In fact, I've taken it apart and reinstalled them, but I still get the same result.  Apparently I must have the wrong spring.

You might check the hole they go in, it might have a burr, find a drill bit the size as the hole and twist it with your fingers, that should rid you of any burrs, OR the spring might be too short.

RickyRifle:
Look at the spring for the safety selector it should be a little shorter and stiffer than the springs for the take down pins. Both take down springs are the same size as stated above by Wingman26. With the spring and detent inserted in the receiver next to the take down pin you will have about 3/16" of spring showing outside of the receiver. If all this checks out one of the springs or the detent is to short.