Hey long shot I love the idea of using the BCG and charging handle from the other upper that will save some money for sure . Would you suggest a go/no go gauge just to be safe ? I would check that out first .
As far as practice building . Not sure thats a good idea . you can and most likely wind up spending more money then needed and have a bunch of extra parts laying around you decided not to use . Trust me I learnd the hard way on this point . I have almost enough parts to build a complete AR just sitting here . All I really need is an upper receiver and barrel . Hum ??? I should totally do that .
I like the idea if you really just want to learn and get the feel of things . I would just upgrade the one you have . That way you will have a very nice gun and not just another average upper that you will most likely put more money it to later and have even more parts laying around
As of this date 8-18-14 at 6:42am I became a proud grandfather I guess I'm officially old