AR15 takedown pin is LOOSE

[he11zna]

I helped a buddy throw a lower together the other night and after building it up and mating upper to lower, I notice how loose the rear takedown pin was.

It would literally slide right out if held ejection port down.
I've never seen this before.

Is it possible the takedown pin itself was machine a fraction too small?

A new pin, detent and spring are on the way, but the detent and spring seem to be doing their job of retaining the pin itself (so it doesn't slide out) it is just loose as a goose, so to speak.

Any ideas?

[RoyJackson]

Originally Posted by he11zna

I helped a buddy throw a lower together the other night and after building it up and mating upper to lower, I notice how loose the rear takedown pin was.

It would literally slide right out if held ejection port down.
I've never seen this before.

Is it possible the takedown pin itself was machine a fraction too small?

A new pin, detent and spring are on the way, but the detent and spring seem to be doing their job of retaining the pin itself (so it doesn't slide out) it is just loose as a goose, so to speak.

Any ideas?

It is a possibility the pin is small...or, the hole for the pin may be a bit large. Since you have a new pin ordered, you'll know soon enough what the problem is.
If the hole is big, you may have to contact the receiver manufacturer. They'll probably replace the receiver, but if you bought it stripped, it'll have to go back stripped. I don't think bushing the hole would work due to the relative thiness of the receiver walls.
So, I hope your new pin rectifies the problem.
No, I've never seen a loose pin either. I have seen uppers and lowers with more slop then I'd like, but the rifles shot fine.

[Kaos]

Could be the upper too. This is what forces some guys to peen their take down lug slightly to create a tighter fit. Usually only an issue on cheaper/budget rifles.

What brand is the upper receiver?

[39flathead]

The pin should measure .250"

If everything measures out OK, you will have to determine what is out of spec, the upper or lower.

If all else fails, install an accuwedge, this is the only time IMO that they should be used.

[joelad]

+1 on the accuwedge. Those things make it nearly impossible to move the pin with the use of a tool.