Hello, could anyone please tell me which AR 9MM upper is easier to work with, as far as dealing with mag blocks, mags, compatibility with my AR15 lower receiver goes. I have been thinking about an Olympic 9MM upper with a Socom mag block and a shit load of sten mags. Is this a good choice, or could I find a better setup.  Would I have to due any changes to my AR15 lower receiver if I wanted to alternate between my 5.56 and soon to be 9MM upper. Please keep in mind that I'm new to this 9MM rifle thing, and I will more than likely have some more questions . Thank you for your time.................

Beerbelly, for me the OLY setup is the way to go. I have 2 9MM carbines 1 is an OLY I bought new and the other is a OLY upper on a DPMS lower. I just put the upper on the DPMS lower added the socom block and sten mags. Just so you know this setup won't hold the bolt open after the last round. Oly is also coming out with a model that takes Glock mags.

Getting back to my setup I have had zero problems using Winchester and Wolf ammo. No FTF or FTE. I don't have any experience with the Colt setup but I would sure like to try on out. As far as costs I picked up a new upper for considerable less that what OLY advertizes  on the EE  the seller even through in a socom block, comp and sten mags.

If you know someone that has a carbine see if they will let you try it out. Whatever you decide either Colt or OLY style I know you'll be happy with it. You just need to own an ammo factory!

i went with colt style for the following reasons mag block is vm hytec . reasons 1 uses uzi mags which are all pre ban , which you still have to comply with here in ny. mags will fit in all standard smg rigs ex: thigh rigs tac vest ect: plus if you own an uzi youre all set or plan to buy one.mag source tapco 12.95 25 rnd , vector arms 32 rnd 35.00 hope this helped

I went with a ASA upper and mag block. It uses UZI mags. No last round hold open. I had bolt ramped. Uses same hammer for 223 and 9mm. I have had no problems with this set up. Mag block loads from top of bottom receiver.

Are any of these 9mm set ups better for Full Auto? There are so many variable that it makes my head spin.
Thanks

Colt 9mm is designed for full auto - buy a 635 parts kit and a mag block and you're in business

Thanks for all your input guys. I'll let you all know as soon as I make a decision, and give you a full range report.