Mid length gas on 20" barrel

[Jbjayzon]

I see a lot of charts online about how a mid length gas system is quite adequate for a 20" barrel, yet i cant find a company that sells them???
System
Barrel Length
Port Distance
Pistol
Less than 10 inches
4 inches
Carbine
10-18 inches
7 inches
Mid
14-20 inches
9 inches
Rifle
20 plus inches
12 inches

[m796rider]

What charts...?

The classic AR is a 20" barrel with a rifle length gas system. For sure on a Grendel, you want a rifle length gas system on a 20" barrel.

[Jbjayzon]

http://www.at3tactical.com/blogs/news/9298047-carbine-mid-or-rifle-a-beginner-s-guide-to-ar15-gas-systems

Mid-length gas systems have become quite popular, and are most commonly used with barrels from 14″-20″ in length. They give the shooter a longer sight radius and reduce some of the wear and tear on the upper receiver. Mid-length gas tubes are approximately 9.5″ and require a handguard around 8.5″-9″ in length. Choices for handguards of this length include the UTG Free Float Mid-Length Quad Rail, UTG 2-Piece Quad Rails, Daniel Defense Omega Mid-Length Quad Rail, Hogue Mid-Length Free Float Forearm, and the Troy Industries 9″ Extreme Battle Rail.

[Jbjayzon]

I don't know..... I was just reading and came across some things...

[LRRPF52]

Sabre Defense made some 20" MLGS guns for some reason. I would never advise it, but they did.

MLGS is a bit short even for 18" barrels, with excessive dwell, but ported correctly, runs all day long.

A lot of that information on that site appears to have been gleaned from posts online, then written into blog posts. The explanation about barrel length and accuracy overlooks the most important factor in shorter barrels having more inherent accuracy if both have the same OD, namely sectional area and rigidity of a short pipe versus long.

It reads like a summary of partial information that has been posted online.

The description of how the AR15 gas system is ok right up until they reach the carrier key, then it departs from reality and explains how a Ljugman AG42 works, not an AR15.

[Clays23]

Could check out x-caliber barrels. Don't know much about them but I know they offer a mid length gas 20" barrel

[ah1whiskey]

i'm pretty sure ADCO can move a gas port anywhere you want and make it any size you want--

the difficult part is getting a grip on "WHY?"

i have several 20" in 5.56, 6.5g rifles and they run perfectly well , very smooth functioning , soft recoil , easy on the parts--
i don't see how moving from a rifle to a middy would help any .

right now i have a pinned FH version of the 14.5" saber 6.5G -- at first i though --"this might be harsh and over-gassed" after i got to running it for a while i now see no need to change the location to middy.


if you want to play around with gas pressurs -- an adjustable gas block might be a better idea than changing port locations?

[Lightning8]

My Sabre 20 inch upper is midlength. Shoots fine. Do not notice any additional recoil.

[Rainman]

My 18" BHW has a mid length gas system and the gun runs great. It is what I specified and how my gunsmith ordered it from BHW. If I do a 20" or longer upper at some point I'll spec a rifle length gas system. As I write this I am sitting here looking at my new Black Friday AA 16" Lightweight upper that conveniently arrived 12/24 and it is also midlength. Hope to shoot it in the next few days when the Aero Precision mount and Badger Ordnance latch show up. Santa did a good job at my place this year.