Just got a new 450 upper and will be mating it to a lower as soon as it arrives.
On a side note as a left-handed shooter I have noticed a trend that there are no left-handed parts just ambi labeled as left-handed. While right-handed parts are right-handed only. This is extremely annoying to me, on a good note i did find this
http://www.brownells.com/.aspx/pid=4121 ... COMPONENTS
Out of curiosity, What would it take to make those work with the thumper?
Thanks for letting me vent.