do you guys know what the difference between an ich and a metric receiver are? because i have an imbel metric kit and i found a blueprint on the internet that is in inches, could i put a kit on one of these receivers if i built one? i have access to a full machine shop, with cnc mills and all that, plus the proper metal and skill, i was just wondering if it was doable.

Thanks alot
Ghost

www.centuryarms.com/receivers.htm

Short answer:  You can build your Imbel kit on either - main consequence is to the magazine you will need.

 The Commonwealth pattern (commonly called "Inch pattern") and the original Belgian pattern (commonly called "Metric" pattern) receivers are functionally equivalent and generally have the same dimensions, threading, etc.  Metric pattern does not use metric threads.   The original Belgian FN FAL rifle was adopted by members of the British Commonwealth and pattern drawings were developed that converted the dimensions to be expressed in inches (rather than mm - hence the term "inch pattern" for production in the UK, Canada and Australia.   Subsequently, the Commonwealth group steering committee adopted a sizeable number of other modifications that also came to further separate the two patterns.   As described in the link - main diffs are:  1) mag well (mags are different - metric mags are more available and less expensive), 2) configuration of the lightening cuts on the receiver (mostly a matter of style), and 3) cuts for the dust cover - Commonwealth pattern (inch) dust cover has tabs on the rear.   If it were me, I'd simply opt to buy a DSA type 1 or type 2 receiver - I own several - very nice.