The M16A2 buttstock is about five/8" of an inch more time then the sooner models. Due to enhanced size it used a longer buttstock screw in addition to a spacer. The swivel is mounted closer for the buttplate. This buttstock is at the moment used about the M16A4: The modification https://kylerzcazw.wikibuysell.com/1078692/rumored_buzz_on_colt_python_6_for_sale