I need help with the upper

[mmd]

Hi

I have tryed a ar15 and got in love and i will now build my own but dont know what to buy.

I will use it in ipsc.
Is it accurcy alot better with a 20" then a 16" barrel?

Is this good stuff or low price **** that will not last for long or/and will not shot any good

- 16" 4140 Chrome-Moly Steel, Lite Contour Barrel, 1-9 Twist, Chambered in 5.56x45mm - A2 Flash hider - A3 Forged Upper Receiver w/Teflon® Coating - GlacierGuards™ Handguards - Complete Bolt Carrier Group & Charging handle - Forged Front Sight Base w/Bayonet Lug

[Constructor]

IMO accuracy with a 20 is not better than a 16 just because of barrel length unless you plan to use iron sights.
Sounds like run of the mill stuff without knowing what brand, 4140 steel is the softest and can wear out quicker than 4150 but, it is harder than stainless.
"Glacierguards" sounds like DPMS to me, I'd look around a bit more JMO.