I am new to the world of ARs so please forgive me if this is a stupid question with an obvious answer. I purchased an Connecticut Compliant M&P 15 Sport (barrel is not threaded and stock is fixed). I will be moving out of state and would like to buy a new barrel that allows me to screw on a muzzle brake. My question is, are all the barrels that I have come across on gunbroker.com that are 5.56/223 compatible in my rifle? I see some that are listed as "Milspec" and am not sure if that means the dimensions/ threads are any different and would prevent me from installing it in my upper. Here is the one I had my eye on:

AR15/M16 M4 1/9 5.56 BARREL AR-15 MILSPEC 556 223 : Semi-auto at GunBroker.com

Please confirm that this barrel would be good to go so I can get this done. Thank you!