Re: Upper Question
My first AR-15 was a Bushmaster lower with the upper being parts liberated from the US Army. It was a fine weapon and I was extremely happy with it right up until I sold it. I think your hybrid should be fine. If it were me, I would investigate an upper in a different caliber so you can have two weapons in one. I particularly like the 5.7X28 round and I see that an upper in that caliber is offered.
I now have a complete Bushmaster M4 with the gas piston system. If you decide on a Bushmaster, you might want to look into something like that.
NRA Endowment Member
Retired US Army
Retired Postal Worker