Need to know the  inside depth of the receiver extension (buffy tube).  
Hence remove the buffer and spring, drop a measuring tape down the inside, and measure from the back inner void to the top end lip.

On the recoil spring, need to know the free lenght of it,

On the buffer, need to know the lenght, and the weight of it.

On the B/C, remove the bolt from it, and with just the carrier and key, need you to install it in the upper receiver with your finger in the back of it, and run it all the way forward and all the way back in the upper receiver.  Is the key binding on the upper receiver slot for it, and when the front of the carrier gets about a inch before touching the barrel extension face, does the gas tube enter the carrier key cleanly.
Note, do this with the charging handle in play next, so you can check to make sure that the top of the key  is not binding in the charging U handle slot as well.

On the buffer, check the buffer bumper roll pin to make sure it not protruding past the edges of the buffer surface, check the end of the recoil spring winds for burs that may be scrapping down the side of the buffer or inside of tube, and take a good look inside the tube for any wear marks.

On the bolt, remove the extractor from it, and if you find a O ring around the extractor spring, remove it/reassembly the B/C with out,  and see if you are still having the charging problem.