i just came back from the range, where I was testing a new laser with my select fire AR.

As I was shooting, the gun stopped working. I took the upper off and noticed that the buffer spring was out of the buttstock, and had come forward. The detent and the spring (if my terms are wrong, it is the spring that goes in underneath the receiver in the pistol grip) flew loose. I was about to find the detent, ie, the part that looks like a cup and holds the spring, but I could not find the spring.


Anyone have any idea why the spring and detent came loose? I've never had this happen.


It was a DPMS TAC2 that I was running with an RDIAS.

Your buffer tube was either not screwed in far enough (thus BARELY making contact) or the castle nut backed off and it somehow rotated just enough to allow the detent/spring to come out.

Thanks, my friend. I had installed M16 parts in the gun. I was wondering if by installing the parts, I did something to mess up the spring and detent.

Make sure it didnt damage the lower. Thank goodness it wasnt a rr.

Likely your buffer tube wasent installed right as that's what holds it in place.

Assuming that it was there is a small chance the upper has the hole drilled for the buffet pin out of spec.

Also make sure your castle but doesn't come loose, use lock tight if necessary, don't stake it though, pain in the ass to remove and defeats the point of the modularity of the ar15/m16

I checked the lower. It wasn't damaged.

Are you sure that the buffer tube is what hold the buffer spring in place? I checked my gun, and it seems that the detent is what holds back the buffer spring from going forward. The DPMS uses an octogonal buffer end piece (if that's what it is called, specifically it is the metal item that is in the big buffer spring and that is pushed back by the bolt), and that's what may have allowed the buffer spring end piece to go over the detent. On all my other ARs and M16s, the buffer end piece is round, so it has no chance of going over the detent.


I did check the buffer tube. It's tight and isn't moving. I'm guessing that somehow the buffer end piece was able to spin and then go over the detent.

The round buffers are early colt buffers the added the flats later to ease installation. You must have early m16 rr's. The tube holds the buffer retainer can u span a picture?

It was an early colt receiver that I was looking at.


I have to get to 50 posts before I can post a picture. Getting there.


 

At the very end and bottom of the buffer tube where the threads are it should have a lip, ie the tube isn't flush, when the tube is installed to the correct number of turns that lip will hold down the buffer pin. It can be depressed to put a buffet weight but the spring under the buffer pin should keep it in place. The large buffer spring and weight likely not the issue, in fact they only came out of the tube after you pulled apart the reciver, they can't come out on their own as the BCG would be in the way.

If it were me I would buy a new mil spec buffer tube, detent and detent spring. When you install make sure the reciver plate and castle but are tight.

Other than that I don't know what else you can do it what would be causing the issue.

is this what your talking about
borrowed pic from other thread

Yes, Pax. That's exactly what I'm talking about.

For some reason, the buffer spring and the octogonal shaped end, in your pic, was able to go over the detent (which you've circled in yellow).

It sounds like the detent came loose because the receiver extension (otherwise called the buffer tube) wasn't screwed in far enough to make sure the detent stayed captured in the lower receiver.    Once the detent came out of the lower receiver pocket, the buffer (and recoil spring) was then free to shoot out of the receiver extension when you opened the upper. (as the bolt carrier held it in place when closed)

If the buffer and recoil spring somehow overran the detent and it is still securely in the receiver pocket it sounds like the detent is out of spec somehow...but your initial post made it sound like the detent and spring came out and the spring was nowhere to be found.

One test to confirm is can you drop the detent back into the receiver pocket as is?   Removal and reinstallation of the buffer detent "normally" requires partially unscrewing the receiver extension for clearance.

The buffer tube (technically, receiver extension) is what holds the buffer retainer and buffer retainer spring in place.  While your buffer itself may have ridden over the retainer (and if it did, it's a poor design on the buffer), but receiver extension should still be holding the retainer in place.

This is the preferred depth of the extension:


But this will work


The difference between the two is one turn of the extension into the lower.

If your receiver extension isn't holding the retainer in then it's either not screwed in far enough or is out of spec.

And, by the way, the retainer is NOT needed for proper functioning of the rifle, it just keeps the buffer from shooting out the end of the extension when you take the upper off the lower.

By any chance do you have a piston upper?  It's conceivable that piston-related carrier tilt might have worn away the part of the extension that holds the retainer in place.

Just because your receiver extension was tight doesn't mean it was screwed in far enough.  Check that first.  It should partially occlude the hole the retainer and retainer spring sit in.

Problem is solved.

The pictures you posted provided the solution, Fred. Many thanks. When I examined the buffer tube on the gun, I noticed that the indentation on the buffer tube was not holding back the detent, thereby allowing the detent to fall out. So I found a youtbe video on how to screw in the buffer tube, and now the detent fits flush into the buffer tube. It appears that at the factory, they didn't screw in the buffer tube far enough. One extra turn solved the problem.


Thanks, gentlemen.