Originally Posted by Kevin Thomas
Unless you're messing with suppressors or have some other special needs in mind, I'd have to agree with the question about the adjustable gas block. No real requirement here, especially in a standard length barrel, like the 20" you've mentioned. A 24" or 26" might qualify as a long barrel (and typical on most competitive guns) but yeah, expansion ratio matters a bunch. The 20" is a good choice to maximize performance in a very manageable envelope.
Thanks Kevin that's what I was leading up to, no need unless suppressed. I cant see the utility of rifles with barrels longer that 20" except on the firing line, but I suppose lots of guys do.
I would pick another stock, if you stick with the barrel in your initial post your going to be so noise heavy your going to end up hating the rifle. A magpul PRS would balance out a 18024" barrel very nicely, or just stick with a standard A2.