[QuarterBoreGunner]

I ran about 200 rounds of CCI Mini Mag through it last night and I'm wondering how stringent I need to be with the gas tube.
Is canned air enough or should I be shooting gun scrubber or something similiar through it?

[boing]

I rekon a couple rounds of .223 would clean it out just fine.

[4v50 Gary]

I'd scrub it with a brush to clean out the leading.

Consider a dedicated upper like Kuehl Arms or something from DPMS or Brownells. The .223 bore is actually .224 and it's a wee bit big for the .221 caliber 22 LR bullet. The tiny lead bullet kinda sorta bounces down the bore leaving a rich pb deposit along the way.