Another option for an adjustable carrier, if you can't find the Gemtech or are leery of the components used (I've heard complaints about the staking and the screws used for the gas key being subpar): http://bootleginc.com/product/bootle...table-carrier/

You could also get something like the MicroMOA Baby Govnah or Black River CustomTune Port, which are gas-restricted gas blocks, so you can tame down an overgassed barrel, but still keep the simplicity of a non-adjustable gas block.