I recently put together an Ar-15 using various parts from PSA and other online retailers. Shot a couple hundred rounds through it with no issues until last week. Went out to the range with a few friends, I noticed I kept having the same malfunction when trying to close the bolt on a full magazine - bolt was unable to close (as in the bolt release button would not even budge no matter how hard I tried to smack it). On top of this, the magazine release would not work reliably when this malfunction occurred, which meant I had to hold down the magazine release and forcible wrestle out the magazine. Note that inserting a full mag on a closed bolt and racking the charging handle worked just fine--it was only unable to feed when the bolt was open and I tried to use the bolt release to close on a new magazine. I removed the pivot pin to take a look and see if there was any obvious issues and I noticed the face of the buffer had pits all around the edges, as if it was slamming into the detent over and over.. Any help would be appreciated.. See below links for images.

https://ibb.co/F3T7BcB
https://ibb.co/CwYzmZT

That buffer is chewed. Tag for out come.

Never seen a buffer beat up like that.

I had a buffer start to look like that

the lowers buffer detent hole was miss drilled and the bolt carrier was not pushing the buffer back as the rifle closed

i bought an offset buffer retainer

https://kakindustry.com/ar15-offset-buffer-retainer-pin/

https://gallowayprecision.com/offset-buffer-retainer-for-AR-15-rifles

Having the buffer retainer is not required

you can pull it out for a test run

when you open the upper, the buffer will want to pop out, but you can run the gun that way

Thank you all for your quick responses. I removed the buffer retainer entirely for now. Looking into a silent capture spring anyways.

Worse chewed up buffer I've ever seen.

Thanks for sharing.

the lower on my 6.8 had the buffer retaining pin hole either mis drilled or had some flash and I was in a hurry, the pin is jammed down in the hole, rifle shoots great.  no damage.  

op, I would replace that buffer.  not sure how you can get that kind of chewed up buffer.  also look at the rear face of the carrier, see what it looks like?