Finally got out to the range this morning to sight in a BM A2 14.5 HB MiniY comped upper that I bought some months ago. Wow! After minimal adjustments I was able to get 1.5 inch groups at 100 yards using the iron sights. I am completely rethinking my plans to equip this thing with an optical sight. It shoots plenty good with what came on it. Also tried the BM 10 round mags that I received last week. I was leery of them after reading some of the reports here but am pleased to report that I had zero problems firing more than 200 rounds through them.
Thanks Bushmaster for the great products!
By the way, if anyone's interested, the ammo I was using was Georgia Arms G223B-2. It was much more accurate than the South American battlepac stuff I started with.