Re:" plastic blanks"

The only blanks I ever saw for the M-60 in Oz were the black plastic variety. The earliest of these had a BRASS heads with the primer staked in, attached to the main plastic body. These brass bits were headstamped "DAG"; Germanicon manufacture from memory. Later Oz production had the brass tail-end replaced by aluminium.

I was of the understanding that the M-60 manufacturer, Maremont, specifically warned against their use.

Two reasons:

1. Being plastic, they carried virtually no heat away from the chamber when extracted / ejected.

2. Being relatively soft, and thus quite compressible, they allowed the locking lugs to hammer into the front of the locking recesses in the barrel extension; chipped lugs were a regular occurrence, as was the practice of stoning the chips and cracks to "restore" the bolt.