As long as the stock has the right tube/buffer you are good to go. It doesn't know what gas you have on there. I've run everything from 17-223 to 458 SOCOMS with everything from pistol to rifle length gas systems on a basic A2. No heavy buffers, no light springs no changes.
The dwell time on the barrel is not going to be an issue for you and many like the mid gas on the rifle length as they say it cuts down the recoil impulse though your is right in the standard dwell length with that 18" barrel.
The secret on running any of these is the amount of gas being run in them. Big port=more gas. I believe in adjusting port size to fit the need rather than fight the buffer weight/spring/BCG battle. Most factory and the majority of aftermarket barrels are over-gassed for reliability from the get go. I don't mind the over-gas if it is a small amount but I do like to run adjustable blocks to broaden my choices of powders since I reload.
Greg
