Shaferhunde: gas rings should be replaced about every thousand rounds for reliability, or if you don't shoot that much, once a season. Sources are all over, DPMS, Armalite, Bushmaster, Olympic, etc. Replace them in three ring sets. They are not that difficult to remove, the use of a straight pin will assist in prying the used rings out of the groove. To replace, just insert rings one at a time and use some lubricant and not a lot of force. Prices on rings depends on who you get them from, but should be under five bucks for all three. Make sure to offset the ring gaps every 120 degrees or so. Put a good quality oil on the new rings before replacing bolt in the carrier, go shoot it a few times and they should be broken in. Your zero might change some, but not much.(End)