AR gas systems?

[Grayfox54]

I own a couple of ARs, but I'm really not into them and don't know much about them. But I am curious about the various gas systems. What's the difference between a standard gas system and a mid-length? What difference does it make? How many gas systems are there? Which is best? 

[scatman]

Gas tube lengths are available in 4 different sizes, pistol, carbine, mid length, and rifle. Couple things to consider when choosing what best suits your needs 1) barrel length, 2) what round your AR is using, such as 5.56 vs .223, 5.56 puts out more gas. 3) is it canned? There's a helpful diagram available with just a short Google that helps a lot.

[deerslayer]

It's all about having the ideal dwell time for gas interacting with your bolt carrier group.  Different barrel lengths need different gas systems.  Mid-length for 16" guns is generally more tame than traditional carbine length and has become more popular recently, especially if a suppressor is involved.  Caleb at Brownell's explains it pretty well:

 

Edited Sunday at 03:24 PM by deerslayer

[Choatecav]

That video was very informative.  Thanks for pointing it out, Deerslayer.

[TNMTBik3r]

Mid-length gas for 16", rifle length for 18"/20" are my setups (5.56, 6.8, and .308).

There are some exceptions to the listed 4 lengths, as a few manufacturers do intermediate or plus lengths. Geissele as an example has their own, or you may see rifle+1" (as an example) for special barrels. 

 

A mid-length gas system with A5 receiver extension/buffer makes a sweet shooting AR.

[Grayfox54]

Thanks guys. 

[deerslayer]

18 hours ago, Choatecav said:

That video was very informative.  Thanks for pointing it out, Deerslayer.

The Brownells Youtube channel with Caleb and Steve is a treasure chest of AR building, tuning, and troubleshooting info.   

[btq96r]

1 hour ago, deerslayer said:

The Brownells Youtube channel with Caleb and Steve is a treasure chest of AR building, tuning, and troubleshooting info.   

It was 10+ years ago, but their videos made my putting together a lower assembly from parts a snap.  And I'm not some fantastic wizard with tools in my hands by a long shot.