I've cut & pasted a blog from a web-site dealing with cleaning in general.
(Joel has written a few articles in Guns & Ammo on proper cleaning of the AR/M-16 rifle).
Chances are, you're not firing ten's of thousands of rounds through your AR. If you were to never even glance at the gas tube, the likelyhood of having a problem related to buildup in the tube is remote.
Your not going to hurt the tube by running a pipe-cleaner through the breech end, assuming of course you don't get it stuck. In my opinion, the benefits of doing this in a civilian pattern AR are minimal.
Note that this article was written before the military banned CLP....
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Cleaning and Lubricating the AR-15/M16/M16A1: the Marine Way!
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The Marine Corps method of cleaning M16A2's includes a regimen of cleaning over three consecutive days after firing. Rags are used at first to get the majority of crud out of the receiver and bolt carrier assembly. The bores are punched (from the breech end) in one direction only (in the direction of bullet travel), using a standard sectional cleaning rod minus the handle (so that the entire rod can go through the bore). Drop the rod into the chamber end, then pull it through from the muzzle; the end with the patch/brush will be the end to exit. Using CLP, let the bore soak for a day or three before final swabbing.
Using CLP (Breakfree is the commercial equivalent) as the sole cleaning fluid, brush the outside of the bolt carrier and wipe it dry with a clean rag. Using the cleaning rod with only one section, swab out the carrier at both ends, paying particular attention to the end where the bolt goes. Using Q-tips, thoroughly swab out ALL carbon deposits on and in the bolt carrier. Using the brass portion of a stripper clip (or other suitable instrument), scrape the hard carbon deposit "ring" from inside the bolt carrier. Follow up with Q-tips. Using pipe cleaners, clean all of the holes in the bolt carrier, including the gas key (don't insert a Q-tip into the key!). Throughly brush and clean the (stripped) bolt in much the same way, paying particular attention to the extractor.
Next, the handguard retaining ring will be cleaned using Q-tips and pipe cleaners. It is a little tricky, be patient. The place where the gas tube enters the upper receiver is called the "clover leaf". Clean it out with pipe cleaners, inserted from the receiver end. Thoroughly clean the front and rear sight assembly using whatever materials seem appropriate for the job. Remove the buffer from the buffer tube and clean it with a rag. Clean the buffer tube with either a cleaning rod and an oversized patch, or stuff a rag down there and pull it out a few times. Next, spray CLP into the lower receiver group. Rag off all the excess and proceed to Q-tip it out thoroughly. It ususualy doesn't get too dirty. I will skip all of the other minor details, such as scraping out all the crud from the buttstock, etc.
Hope this was of some help.
Sgt Joel R. Dunton, USMC
MCAS New River, NC