Well had her opened up tonight. after a good go at the loctited rear block involving a hammer and spanner
could not find the source of the rattling, and a lot of the twang has gone
it actually wasn't as bad as I thought it would have been.
piston seal was fine, there was quite a bit of grease infront of it tho, and loads in the trigger.
some metal shards in the piston and in the comp tube causing the grinding on cocking.
the spring guide wasn't as tight as I thought it should have been, and the spring is quite loose in the piston, hence the twang
spring ends were cut