[Powderman]

Sounds like someone forgot the buffer itself.

1. Clear the firearm.
2. Look at the buttstock.

Fixed? Get a nice sized flat-tip screwdriver, and unscrew the rear upper stock screw. Slide the buttstock off the buffer tube. Watch for the detent pin spring and detent pin that will come out of the small hole under the forward part of the buttstock.

Collapsible? Get the appropriate spanner wrench, and unscrew the lock nut. Remove the buffer tube, and let the spring expand slowly.

On the fixed one, get a crescent wrench, have someone hold the receiver flat on a table, and give the wrench a sharp rap, counterclockwise. This should break the tube free.

Remove the tube and spring, and remove the bolt.

Inspect the bolt carrier for damage; peening, shaving or deformation.

Clean and service the bolt and carrier.

Replace the detent pin that holds the buffer in, and the spring.

Inspect the buffer for damage, and inspect the spring for kinks or damage. Replace as necessary.

HINT: A drop of oil in the detent spring will prevent rust and assist in smooth operation.

Reassemble and test fire.