Change the orifice? The hole can be enlargened but to close it it would have to be plugged and then redrilled with a smaller hole. There's that gas port tube that goes between the barrel and the gas cylinder that can be changed.
Here's the problem with either of those concepts. You change the amount of gas flowing to the action. Now the ejection will be slower, allowing the brass to drop at your feet. But at what price? Reliability. Change the ammo and it may not work. Nope. If someone hands you ammo, you don't know its origins and it may jam in your piece. That's OK for range situations but in hunting conditions that's one less coyote/rabbit or what not that is going down. In self defense, you may have a single shot whereas you have multiple assailants.