No need to short cut.
I've never built a L1A1 before and have aquired some parts and would like to get started but I am not aware if these can be assembled together.. What I have is a L1A1 Build Kit from I.O. a metric receiver (STG 58 DSA) and a Imbel barrel. These are of course a combination of metric and standard but can these 3 work together or am I going about this all the wrong way.
You have to use either a metric or inch gas system. If you can press off the metric gas block and fit the inch one on and use the rest of the inch gas parts thats your main problem. If not you have to get a metric gas set up. You shouldn't need the breaching washer with the metric barrel and receiver though.