I am in the process of building a dedicated 9mm AR. The foundation of the build is a Double Diamond 9mm lower and the upper receiver being an ASA dedicated 9mm side charger. As many of you know, BCG options are fairly limited and IMO fairly primitive as well, at least as direct drop in. My question is, what are my other options? I know both CMMG and RRA offer an out of the box 9mm bcg but would it be possible to purchase another BCG or carrier manufactured for a standard 223/5.56 and have it modded for my application? If so, would it offer me any benefit? Money isn't exactly an issue for this particular build but, at the same time in have no interest in throwing $100 bills into a wishing well and not be rewarded. Any help or advice would be much appreciated.

I thought that might be the case. Just looking for a way to step the rifle up a level, I guess.

9mm isn't a bolt carrier, it's a bolt.  One piece, completely different method of operation and different parts configuration than 5.56.  You can throw as many hundred dollar bills as you want at a 5.56 bolt carrier, you're not going to make it a 9mm bolt.

If you just feel the need to throw some hundreds around, there are folks who have made gas operated 9mm builds.

ASA can't provide you with the bolt as part of their upper?

Not really looking to spend money for the sake of spending money, I have looked into the GP system option but I believe that would require some machining on my upper receiver. And probably a sleu of other issues I am sure.

ASA doesn't have any available at the moment. That is not a big though. Modding the BC to function with the upper is just a simple mill.

Ron Williams makes a 9mm DI upper. It uses a regular AR bolt carrier. I'm sure you could work out a deal for him to build it on your ASA receiver. If I remember correctly, he said that there just wasn't enough gas volume to run a gas piston 9mm. The only draw back is that you need to be a reloader to run the 9mm DI upper. I haven't shot one of his 9mm uppers, but I can assure you that his 45acp uppers are so much nicer than a blow back system. His DI uppers weigh less & exhibit less recoil than a blow back.

I have heard good things about them. I do generally load a lot of my own stuff but it seems like that has been the case less and less. And realistically I need this rifle to shoot anything I shove down its throat.That is an option iI may look into though. I have some time to think loLon it and research it while I am waiting on the BATF to get my stamps to me.