Here's the info Roy from Aussie Arms sent me:
1/4" Barrel retaining Screw.
1/8" Folding stock tention screw.
3/16" Grip retianing screw.
3/32" Bolt release retaining screw.
5/32" Gas Block retaining screw.
2.5mm Stock location screw (not part of XCR, but part of a M4 style stock)
To this you can add:
1/8" M4 Folding stock tube adapter mounting screw (it's inside the receiver)
This info should be part of the XCR manual.