So I finally got the chance to finish my ultimate AR build, the last thing I need is a gas system. My question now is who makes the BEST one? Also what length should I get it having a 18inch barrel 1.8 twist. Keep in mind I'm only looking for accuracy. Quality is very important for me! this is my hand guard. 

 

 http://www.seekinsprecision.com/product/handguards/sp3rv3-mod-rail-16.html

The "gas system" is dependent on where the gas port is drilled into the barrel.  I would assume that yours is either a rifle length gas system or a mid length (ie middie) gas system.  Once you have determined that, then need to buy the appropriate length gas tube.

EDIT:  Based on your post, I'm guessing that what you are actually looking for is a gas block, maybe?

I was in the same position not very long ago. I finally wound-up with a SLR adjustable gas block and intermediate length gas system.

WOA, Noveske, Compass Lake and a few others all make Int. length barrels

I just built an SPR last year and an AR10 this year, with another AR build in preparation. One thing I learned, with the stupid NJ laws, and pinned muzzle brakes, is to go with a 2 piece gas block. You can either go with the standard block from YHM or an adjustable from JP (a bit more expensive). I got the JP block for my AR10, and will be replacing the one on my SPR with the same JP block.

The handguard itself should not dictate the gas block unless you are using a high profile block such as a piston system or a block with rail or sling mount. but the 2-piece blocks from YHM or JP will fit under most handguards.

My $0.02

18" barrels work fine with rifle length gas. No real issues. So no need to go shorter. 

In terms of gas block the JP JPGS-9D two piece adjustable low profile is the answer, especially if going with a long hand guard. It's two piece, so if needed you can take it off despite having a pinned muzzle device. It also fits under slim handguards. 

 

If going shorter handguard than gas system, you have a few yankee hill 2 piece gas block options, a number of them with flip up sights. I own some, and all the more recent purchases getting the gas hole to align is a bit of a pain. They have also gone up in price to the point they aren't cheaper than the JP gas block I mentioned. 

They do have a new hinged gas block I have not met in person, but is kind of neat as well. It's only $50 at midway, but is not for sale yet it seems. YHM-9345

 

 

13 minutes ago, raz-0 said:

 

They do have a new hinged gas block I have not met in person, but is kind of neat as well. It's only $50 at midway, but is not for sale yet it seems. YHM-9345

 

 

I saw that one also, looks very interesting. But I don't think YHM has released it yet for sale. I will use it that or the JP for my pending build.

On ‎6‎/‎19‎/‎2018 at 10:14 PM, Scorpio64 said:

The "gas system" is dependent on where the gas port is drilled into the barrel.  I would assume that yours is either a rifle length gas system or a mid length (ie middie) gas system.  Once you have determined that, then need to buy the appropriate length gas tube.

EDIT:  Based on your post, I'm guessing that what you are actually looking for is a gas block, maybe?

I was thinking the same thing...…… You say you have an 18 inch barrel with a 1:8 twist? You bought a barrel not pre drilled for a gas block?