School me on gas systems (specific questions below)

[alamo5000]

I am building a 6 ARC upper and now I am looking for the barrel I would like. One of the questions I have is that some of the barrels I see are "+1" or "+2".

I assume this means +1 or 2 inches in length of the gas system. My question would be 'why'?

I understand when you go shorter you have to have a short enough gas system, that's pretty easy, but I don't quite understand the reasoning behind going longer that 'standard'. From a straight up functionality standpoint I am not sure what purpose or benefit these extra long gas systems serve.

The only thing I could even remotely think of is in relation to dwell time but I still haven't wrapped my head around the reasoning.

[alamo5000]

Additional information that you may (or may not) care about... looking for a barrel probably in in the 22-24" range although I have entertained going as short as 20.

The goal here is to have a long range target gun with the ability to get out as far as possible. I watched a video about a week ago where a guy took his 6ARC out to 1800 yards with successful hits. Given it was out of a bolt gun but more than likely I want to be able to hit to 1,000 to 1,400 on a regular basis because that's where my available space is. I won't be shooting that far all the time of course but I like the capability.

I am going to have to nerd out on ballistics some more before I make a final choice.

I also don't want an insanely heavy barrel. I tried one like that before and I did NOT like it at all but where the breaking point is weight wise I don't know.

Cost isn't a factor provided I get something good. Looking at carbon wrapped barrels too but not that familiar with them.

If I could find something like a Fluted Rainier Ultramatch in the length I am looking for I would jump all over it but they don't have 6 ARC. I am just not that familiar with brands as many of you are so I have to read up before making the call.

[alamo5000]

https://www.youtube.com/watch?v=sBzmx2KHEA0