would I be alright if I go with 300amps, to power up a 5 unit apartment complex, each having a 100amp service in them. these units are very basic, no range circuit, no dryer circuit,exc. they do have ac unit 40 amps

You need to do the actual caculations using section 220 to determine the size of the service conductors and main Sw. You can not guess and expect to be correct.

Bob is correct. I am closing this thread, all replys can be here. https://www.electrical-contractor.net/ubb/Forum1/HTML/005372.html

Roger