Noob Question Difference between A3 Upper and A4 and more?

[volks_r_us]

I finally started builting my first AR even if I never handled or fire the Freaking beast

So I am trying to figure out if there is a difference between A3 upper receiver and the A4 ? Questar has some listed A3 and other A4 I dont see any visual difference. I am going for a precision bench rig.
I wanted the DPMS hi rider upper from Brownells but I have not yet figure out the paper work BS.

I read somewhere that getting a FA bolt bolt would help very Sligtly accuracy.
Any feedback on the CMMG that are on special at Questar ?

Thanks guys

 

[P0WERWAGON]

A3 - flat top
A4 - flat top with numbers

pretty much the same.

personally i wouldn't spend money on the "high rider". once you get bored of it, you are stuck with the goofy lift kit it comes with.

FA carrier is not for accuracy, it is heavier. slows the bolt movement because of the weight. helps the cycling on short barreled guns. not really a big deal until you go smaller than 14 inches. normal carrier works just fine in 95% of the guns out there.

CMMG are fine. i have a couple. nice kit.

 

[Paulinski]

A3 = rifle feed ramps
A4 = M4 (extended) feed ramps.

 

[BattleRife]

A3 uppers and A4 uppers are nominally the same thing. The last fixed carry handle upper in the AR-15 series was the AR-15A2, so it stands to reason the flat top would be the AR-15A3. On the other hand, the last fixed handle in the US military was the M16A3, so the flat top was the M16A4.

Some manufacturers follow the AR system and call their flat tops A3, some follow the military nomenclature and call them A4, but they are the same thing. Details about RIS numbers and feed ramps are due to manufacturer and are NOT a factor in the designation.