The idea of being able to shoot 22 through an AR was one the selling points I was looking at before I bought my first AR.  When I went to my local gunshop and talked with my gun guy he downtalked the Ciener conversion saying that it would ruin your rifle.  He also told me that after shooting 22 the bore needed to be extensively cleaned out before switching back to 223 or bbl damage would result.  I was gun ignorant back in the day and beleived everything gunshop guys said.  Nevertheless I bought the Ciener kit anyway, but I still take the time to scrub out the bore before going back to 223.  The more I learn the more I think this is nonsense but I would like to get some hard facts from the experts here about this before I stop.  I know the 22 bullet will leave piles of crap in your barrel, but will this really cause damage if a 223 round was then fired through?  This is the question?  

After every brick of .22 just fire a mag of .223.  If you don't the gas tube will clog up and you will have a single shot .223.  Or better yet pick-up a used 1/12 twist upper and dedicate it for the Ciener kit - That's what I do!

Get a dedicated 22LR upper and your accuracy will improve.  The .223 bore is actually a little too big for 22LR.  Also it eliminates the whole gas tube problem.

I know that the 223 bore is something like 4 thousandths of an inch too big and rifling is way to fast for 22LR.  I just want some facts about this myth that all the lead deposits in the bore will cause damage if not cleaned out before a 223 round is sent down there.  Just from context of other posts and other stuff I`ve read I don`t think it will do any harm I just want someone to say it in som many words

I'm not really too concerned with accuracy for the 22 conversion.  My 1/9 twist barrel is nothing close to the 1/14 that a 22 round needs and the oversized bore doesn`t help either.  Eventually I will probably get a dedicated upper purpose designed for 22 but for now ithe Ciener kit is good  for low cost plinking.

I usually shoot 200 - 250 rds of .22 in a practice session.  I then run a bore snake twice through the bore, wipe out the upper receiver with a rag and shoot 2 .223 rounds to make sure the gas system is clear.  

I used to clean the bore after shooting .22 but I have never visually seen any lead deposits in the bore and never saw any evidence of lead on the patches during cleanup.  As long as you are shooting semi I don't think you will have a problem with lead.  When shooting cast pistol bullets I could see the lead in the bore and I saw lead on the patches.  The .22 round does tend to leave a lot of powder residue so I just use the bore snake to clean that out.  Every so often I use gun scrub to clean out the lower receiver.  I don't want to get a dedicated upper because I want to practice with the upper I always use.  During my practice sessions I am just knocking down the steel plates practicing my CQB shooting so I don't need the accuracy a dedicated upper might be able to give me.  

Of course YMMV...

Well, a quick look in the Army T.M. shows their solution to clogged gas systems and lead build-up...just shoot it on out!

Continuous firing (400-1000 rounds per weapon) of
cal.22 rimfire ammo will result in lead
particles fouling the M16A1 rifle gas system. This
will cause the weapon not to fire in either semiautomatic
or automatic mode. However, firing
regular M193 5.56-mm ball ammo will clear the gas
system. You should therefore do the following to
prevent permanent blockage of the gas system and
to clear the rifle of fouling:

– At the end of each training session .(typically
400-1000 rounds per weapon), remove the
rimfire adapter and reinstall the bolt carrier.
Fire a 20/30 round magazine of 5.56-mm
M193 ball ammo in the automatic mode in
short bursts of 4 to 5 rounds.

– If the rifle won’t fire in either semi or automatic
mode, manually recharge and fire the weapon
(using 5.56-mm ball ammo) for up to 10 rounds.
Then fire an entire magazine as described
above. This will clean the gas system so you
can resume subcaliber firing.

I suppose if you get it hot enough, any lead build up will just melt away!

Thanks guys.  That is exactly what I wanted to know!