Help me Select Parts for my Middy

[MMH]

I'm trying to spec out the rifle that I want to build. Want to get the order in - worried about AWB coming soon! Anyway, building a 16" middy & getting the following features:

• Flat Top upper (A3 or A4 which one do I need)
• M4 feed ramps
• Middy barrel, 1:9, chrome moly, 5.56 chamber (wanted a wilde but can't get it now)
• Bolt – std (not chromed) – AR-15 or M16?
• Gas block – std. steel but one that can mount flip up sight to, or should I get the one w/ a forged front sight?
• Stock – M4 7 position
• Hand Guard – Std 1 pc. Free Float Alum. Tube (will machine my own FF 4 rail later)
• Rear Sight – YHM flip up (is this a BUIS?)
• Front Sight - YHM flip up on steel gas block (or should I get teh forged front sight?)
• Pistol Grip – std 0

What do you guys think?

[Legion_Prime]

I'm trying to spec out the rifle that I want to build. Want to get the order in - worried about AWB coming soon! Anyway, building a 16" middy & getting the following features:

• Flat Top upper (A3 or A4 which one do I need)
• M4 feed ramps
• Middy barrel, 1:9, chrome moly, 5.56 chamber (wanted a wilde but can't get it now)
• Bolt – std (not chromed) – AR-15 or M16?
• Gas block – std. steel but one that can mount flip up sight to, or should I get the one w/ a forged front sight?
• Stock – M4 7 position
• Hand Guard – Std 1 pc. Free Float Alum. Tube (will machine my own FF 4 rail later)
• Rear Sight – YHM flip up (is this a BUIS?)
• Front Sight - YHM flip up on steel gas block (or should I get teh forged front sight?)
• Pistol Grip – std 0

What do you guys think?

M4 feed ramps are not a bad thing to have but in a semi rifle they are not necessary. Basically, if the upper has them, no problem but I wouldn't pay extra for them.
1:7 twist will allow you to use heavier bullets than a 1:9 will but this will depend on what you plan on running through it.
The M16 Carrier will lower the cyclic rate slightly, between that and the midlength gas system you should be able to use a standard car buffer without problems.
Your front sight is going to be a matter pf preference and how long a FF you are going to use and what type. I would go with a rail mount front sight if you are going to go with a long rail that will cover the gas block or are going to be mounting a 1 piece FF. A two piece Railed FF will be able to put on a rifle with a standard front sight but a one piece will necessitate it's removal.
I have never seen a 7 position receiver extension before, who makes it?
The YHM should be fine for aBUIS, that's going to come down to what you prefer same with the grip. An A2 grip will work fine but there are a myriad of options on this so you can change this out easily with just one screw. (Make sure you don't lose the selector spring and detent though)