I'm thinking of getting a complete 9mm RRA gun and then installing a Hahn top loader so that I will 1) be able to reliably feed hollowpoints and 2) so that I don't have to use my 223 lower (because of the different buffer).  Am I correct on these items?  

Also, would this setup make the holdopen function with Colt, modded UZI and Promags?

Thanks!

I would try the RRA first and see if it has issues.  Some work fine with all kinds of ammo, some do not.  Unless the RRA block is permanently attached, the Hahn should work in it.  Also, the RRA works well with the new promags and the bolt holds open.  Not sure if that's the case with the hahn.  My $0.02.

thanks, any idea where to get the Hahn unit?

Quoted: thanks, any idea where to get the Hahn unit?

Check Brownells.com

Here's the Hahn site: http://www.hahn-precision.com/
I am not certain which block RR uses (a few years ago it was a 1 piece identical to Colt) and whether they use the extended 9mm bolt open hold or the 223 unit. If the AR15 is deicated, I like the new Hahn drop in from the top which uses std 223 bolt hold.

I have the Hahn Top loader, it works great.  I would suggest it over the RRA blocks, I've had bad luck with the RRA blocks.

fq1234 - please tell me what you mean by "bad luck"

Quoted: thanks, any idea where to get the Hahn unit?

I got mine from  ameetec.  It kicks ass.

Quoted: fq1234 - please tell me what you mean by "bad luck"

I've tried several different blocks.

My first was an RRA bottom loader.  It took a little work to find the "sweetspot" in the magwell.  If it wasn't in there in just the right position, it wouldn't run right.  I used blue locktite to try and keep it there.  After I had it for awhile, it stopped running smoothly.  I had a lot of FTE.  I think it was ejector related.  It wasn't loose and everything looked good, it just stopped running reliably.

I then got an RRA top loader.  The fit was VERY tight, which I didn't mind but it was difficult to get the upper and lower together.  The 9mm magwell on the toploader was too tight for my 40 round mags and several other mags I tried.  My 25 round Uzi mags fit though.

I also tried the Hytech Uzi block.  It seemed to work fine the short time I had it.  I didn't really like the mag catch or the fact that it sticks so far out under the magwell.  It would only work with Uzi mags so I was unable to use many of my other mags that weren't Uzi mags (like the 40 rounders).

I decided to go with the Hahn block.  It feeds HP and flat tip bullets reliably, all of my mags fit in it loosely, it won't come out, and hasn't hiccuped yet.

Quoted: Quoted: fq1234 - please tell me what you mean by "bad luck" I've tried several different blocks. My first was an RRA bottom loader.  It took a little work to find the "sweetspot" in the magwell.  If it wasn't in there in just the right position, it wouldn't run right.  I used blue locktite to try and keep it there.  After I had it for awhile, it stopped running smoothly.  I had a lot of FTE.  I think it was ejector related.  It wasn't loose and everything looked good, it just stopped running reliably. I then got an RRA top loader.  The fit was VERY tight, which I didn't mind but it was difficult to get the upper and lower together.  The 9mm magwell on the toploader was too tight for my 40 round mags and several other mags I tried.  My 25 round Uzi mags fit though. I also tried the Hytech Uzi block.  It seemed to work fine the short time I had it.  I didn't really like the mag catch or the fact that it sticks so far out under the magwell.  It would only work with Uzi mags so I was unable to use many of my other mags that weren't Uzi mags (like the 40 rounders). I decided to go with the Hahn block.  It feeds HP and flat tip bullets reliably, all of my mags fit in it loosely, it won't come out, and hasn't hiccuped yet.

+1.  I have never tried the Hytech block, but I have had exactly the same results with the RRA and Hahn blocks.

You may want to look into buying an RRA upper by itself (perhaps from ADCO), then getting a lower to setup for 9mm to use with it.  It may actually work out better (i.e. cheaper/faster) than buying a complete RRA 9mm and a Hahn block, and then trying to sell your leftover RRA block.  Just a thought.  If you don't want to bother, no worries from my end.

My Hahn block works great with Colt and modded Uzi mags, but didn't work with ProMags.

BTW, I'm in Farmington.  If you're close and want to check out mine, feel free to e-mail me.  I also have an account with Brownells and would be more than happy to pass along my discount if you want to buy your Hahn block or anything else through them.

MY RRA block has never givin me crap.