I first owned a 15-22. I bought a 15-Sport recently. Due to the time-sucking holiday season, I've not been able to get to the range. I have cleaned it.

The very basics of field stripping the 15-Sport is the same as the 15-22. Cleaning the barrel is the same process.

The difference is the the 15-Sport's bolt carrier, bolt, & chamber. For the initial cleaning, I followed the printed directions step-by-step. I had no issues.

When you have everything taken apart, you can see how the parts interact as a complete system. What I can see:

1. At some point, I might need a pipe cleaner to swab out the gas key.

2. Carbon buildup will most likely be at the bolt tail, and inside the bolt carrier. A soak in carbon cleaning solvent should do the trick.

3. Old school cleaning should work well. If I need to make things easier, there are special tools to make the process scraping off carbon quicker. (CAT M-4, CRT-15, dental picks, etc...)

4. I'll pick up an AR chamber brush the next time I'm at the LGS.

Now regarding how the gas block basically works...

The front A2 sight post mates with a port in the barrel. This redirects a portion of the hot gasses created by the propellant down the gas tube, into the bolt carrier gas key.

The firing sequence begins about 7:33 into the video. Gas block about 10:00 into the video.

The M16 Rifle (1966) - YouTube

I love the old military training reels. Another favorite is the military promo film reel on the Armalite AR-10.

The Armalite AR-10 Rifle - YouTube