Gas length for 16 inch 300AAC?

[Miltonboro]

Gonna build a 16 inch 300AAC upper and I see the barrels are commonly available in either pistol or carbine length gas.
I'm never gonna run subsonic ammo or use a suppressor on it, so my question is will a carbine gas length 16" barrel reliably run all the typical 110 thru 150 grain ammo? Are pistol length gas 16" barrels only necessary for the 220 grain subsonic ammo?

 

[no4mk1t]

Gonna build a 16 inch 300AAC upper and I see the barrels are commonly available in either pistol or carbine length gas.
I'm never gonna run subsonic ammo or use a suppressor on it, so my question is will a carbine gas length 16" barrel reliably run all the typical 110 thru 150 grain ammo? Are pistol length gas 16" barrels only necessary for the 220 grain subsonic ammo?

My first 300 BLK was 16" carbine gas, non adjustable gas block.
It would cycle supers fine.
With subs, it was a picky eater. I had to use AA1680 to get subs to cycle and not go super sonic. Even then, sometimes it wouldn't lock back. I gifted that upper to a friends son for his 12th b-day. I just got a text from him that young son has killed two deer with it and is happy as a clam.

The uppers/barrels I have bought since then have had pistol gas and an adjustable gas block because I shoot mostly subs.

So, for your situation, carbine gas will work fine if you know you'll never want to shoot subsonic.

Keep an eye on PSA's website. With Veteran's Day around the corner, they just might put BLK uppers on sale.
Find the one you want on the website and click the option to receive an email when it goes on sale.
Daily Deal is another possibility.

 

[clm2112]

Pretty much the same experience. Using supersonic 300 Blackout in a 16" barrel with a carbine length gas system was no problem at all. Also using it in a 10" pistol with a pistol length gas system was no problem. I played with different weight buffers to adjust the angle it ejected, but it worked with all of them in both configurations.

I seem to recall the original AAC product for AR conversions was a 9" upper with a pistol length gas system, though my first experience was with a 16" AAC made 300 blackout barrel on a bolt action Remington (obviously no problems with the gas system there...except from the burrito )

Probably the only thing that would give me pause would be a 16" barrel and a pistol length gas system used together... though I can't think of any reason someone would make that combination. The long dwell time of pressurized gas would not be healthy.

 

[no4mk1t]

Probably the only thing that would give me pause would be a 16" barrel and a pistol length gas system used together... though I can't think of any reason someone would make that combination. The long dwell time of pressurized gas would not be healthy.

I have a 16" with pistol gas. It works fine when using an adjustable gas block. Fire single shots and open the setting half a turn at time until the bolt locks back on an empty mag. Another half turn for when it gets dirty.
This is the only combo that gives reliable operation with subs and supers with 16" barrel. You can use one of the "H" buffers to soften the recoil with supers if desired.

All 5.56 AR's, even with rifle gas, are over gassed, with the old XM177E2's being a prime example and worse offender. Today, just use an adjustable gas block and tune for the ammo being used.