You can keep the same buffer and spring in your AR no matter what you shoot.
I have an H3 (Extra Heavy Buffer and Xtra Action Spring in my AR and I shoot everything .... pistol powder cast boolits, factory, and reloads.
A good friend of mine, Mike Pannone, wrote an article awhile back that you might want to look into.
http://www.defensereview.com/the-big...m4-unreliable/ In this article he does a very good job of describing the function of the buffer, spring, and extractor.
In all actuality ... it's probably not what you would think! It's probably the fact that his extractor is used to heavier loads and is worn in. He needs an extractor spring upgrade. I've seen it dozens of times. I even ran across one rifle that wouldn't fire WCC new production whatsoever. Every time I would fire a WCC cartridge it would fail to eject.
Trust me .... you need to adjust your platform to work with the amount of gas that is pushing the BCG. The 9mm platform will work fine. Think about it ... what do you think they use to cycle the 9mm AR platforms? They usually utilize a few grains less than what you are using.
One last thing to check ... take your Bolt Carrier Group apart and make sure it is spotless inside and out. The 3 rings on the back of your bolt .... make sure they are staggered and not in line with each other. I have seen this happen in some direct impingement platforms where the gas escapes the keys on some models.
Take my advice or don't ... I'm only trying to help and shed some light on the problem with the experience I have.