should drop right on in. I have put both the sps-t and the 5r in one and have not had a problem whatsoever. Actually putting them in the ai was the best upgrade I have done to any of my rifles barring rebarreling and such.
My 20" .223 Rem Tactical doesn't fit in my AICS (probably three years old). It will drop in but the saftey can't be released. Needs a bit machining out. Put the AICS back on my .308VSF where it belongs and the HS it came with is now fitted to the .223.