I've been real happy with my Bushmaster .223 rifle -- it seems very well made.
While many find the .223 to be a mild cartridge - lacking the necessary knock-down you would hope from a miliary round, .308 seem a bit much for a high rate of fire. I like it in my tricked out M-14 for single long distance shots, but it seems like it would be tough to handle on full auto. Although that particular cartridge was suposed to replace the 30-06 which was completely unmanageable on full auto.
I have the .223 also. It is a very well made and reliable rifle.