First time builder

[Kpl1775]

[Red*Lion]

I would guess that a good number of folks would suggest a mid length gas system. I assembled a new upper using an 18" barrel with a rifle gas system using an rifle H1 buffer. My opinion is that you will be fine going either way. Rifle length should give you a bit smoother recoil.

[VASCAR2]

[mdram]

im use a 20" with a 4.3oz buffer (https://www.righttobear.com/Kaw-Vall...peckit-4.3.htm) and RLGS with adjustable gas block

[Kpl1775]

[mdram]

.75?

[Kpl1775]

[drewthebrave]

As long as the barrel maker sizes the gas port properly, you'll be fine either way. While a Rifle length gas system will probably be more tame, I have an Alexander Arms 18" Midlength system and I have no issues with it. I would pick the barrel that you feel has the best combination of price, features, and availability and not overthink the gas port location. Besides, with adjustable gas blocks now being as affordable as ever (see Wojtek Weaponry), you might as well get one regardless of your gas system.

[1Shot]

You can split the difference between mid and rifle length gas with an Oden Works barrel. I have an Oden Works 18" intermediate length gas with their "tunable" gas block wide open and I run just a standard carbine buffer and it runs perfect. This barrel came as a package deal with the gas block, tube and bolt carrier group. It is very accurate.

[Kpl1775]

Thanks everyone for the advice.