I've been offered a Federal Arms H&K 308 with 6 mags for $800. Federal Arms has been purchased by Century Arms Int. What is the connection with H&K? It seems likely to me that this gun is made from a bucket of left over parts maybe with some H&K parts.
Google it, and read up on them. I would let that one pass on price alone. 550.00 is more reasonable. There are some safety concerns on the Alum. receivers. Read up and you make the call.