hi Paul
The C8 was probably a sluggish performer even when it left the factory
The book I mentioned would be a good aid for you. I have scanned the book but I have mislaid it somehow. It is on a CD or a stick . I will have another look, if I find it I can send you a copy. The book , published by MCC themselves, covers all of the miltary models , maintenance instructions and specifications . I do have the photocopy of the book itself , if all else fails I can send you the hard copy but you would have to return it .
Also your earlier query re the serial nr . Not sure - as it is a GS version , it isn't among the C8's listed in the AWM books which were all portees.