For the record I never had to change out anything I just did it for experimental reasons, but I think if you kept up with regular parts maintenance the gun will run like any other M4..That being said other companies on the market make a superior longer lasting rifle in many regards, Shrubmaster seems to cut corners on some things but goes above in others...Most of there rifles are built for civilian export reasons I would say..but LEO and other duties they seem great. Mind you the model I had was built very well to MIL/Spec standard minus the BCG and semi lower and civilian buffer tube and stock...
Some guys in the US hate them and for good reason but I have never seen any bad CQ issues with them per say in person.......
In today's market I find the go too rifles are obviously KAC,Noveske,LMT,DD, and BCM for DI to name a few, one thing I have found is many companies have there die hard supporters that comment on many other manufactures based on jumping on the new bandwagon.
I find the BCM craze a little irritating in some regards..