Help - AR-15 barrel extension pin came out!

[wwhitby]

I have a AR15 carbine that I bult about 20 years ago. Today I was swapping out an old A1 upper for a flattop upper (BTW, using an upper receiver vise), and I noticed that I could wiggle the barrel back and forth in the slot where the barrel extension pin goes in. So I removed the barrel and I was able to pull the barrel extension pin out with my fingers! I put in back in, tapped it ldown, but I noticed after I tightened up the barrel that the feed ramps appear to be slightly off center. So I removed the barrel and noticed that the pin was loose again.

So, can that barrel extension pin be replaced with a new one, or should I be looking for a new barrel, or what is going on? I'm somewhat freaking out, since this is my SHTF carbine.

 

[mjsdwash]

m&a should have them, midway does... any ar parts place. cmmg too. around $2 last i saw

 

[mtrmn]

If you are merely concerned with the pin possibly falling out on it's on, it won't once the gun is assembled.

If you are concerned with barrel/upper alignment (and I think you are) maybe try to hold a backup on the barrel with a strap wrench while you tighten the barrel nut. This is assuming you are using a holding fixture for the upper receiver in a vise. Once the nut is properly torqued the barrel should be incapable of moving.

If the pin has a lot of clearance in the barrel extension or in the alignment slot, then something is wrong with the pin, the extension or upper receiver. Can you wiggle the pin sideways in the hole?

I'm sorry I didn't notice how old this thread was. Probably already fixed by now.