I just finished the sand blasting of the 2nd generation Inokatsu GBB M4! Amazing the thin layer of "I called oxide harden coating on the bare aluminium surface - anyone knows the real term can correct me!" is very tough to get it sand blasted and took one hours to get it done! However, sand blasting also harden the raw aluminium surface but without acid protection function! While the PRIME upper receiver and the bolt are very easy to sand blast 20 minutes get it done. Now took $$$$ out of my pocket and I should have save my $$$$$ for the ........ 2009 verison.
I suspected the NEW 2009 INO GBB M4 is the GBB M4 OF THE YEAR to hang onto our bed room wall. (of course depend on your pocket extra $$$$$)