I am thinking that with a 5.56 rifle shooting 223 that there is a safety net if you get near max 223 loads, right ?
I think it is safe to say there is a wider safety margin with a gun like the CZ 527 than the AR15. I could be wrong on that. I dont have actual data on how the guns might react to say ... a 100% over pressure. I guess its either the barrel or the reciever/bolt that fail. Or all the gas gets vented and hopefully you dont loose a hand. A hand is better than a head!
Some re-loaders will increase charges until they see pressure signs and then back off. That is supposed to be an easier game to play with a bolt action. I stay away from the max, but; I like to at least test fire a few loads that have a heavier charge than the one I settle on. I think, if you had to choose a gun to screw up, your luck might hold up better with a CZ.
I am a firm believer that the best way to achieve greater velocity is to go to a larger round. In this situation that would be a 22-250.