Aggressive brakes like that usually perform real well. I don't have the M4-72 but I do have an APA Little ******* designed with ports that angle back about the same on my .308. Tested one of the best performers as well as one of loudest and obnoxious to bystanders. Ain't no free lunch with brakes.

If you get around to installing a free float handguard, one thing to consider is an adjustable gas block to reduce felt recoil. I don't have a Sport like you, but my primary AR has a 16in barrel and carbine gas system like the Sport. Adjustable gas block made a big difference.