I have been searching and reading for the past hour. I am really stumped on what mag block I should get.

First...a question about the new RRA block. Does it snap in and use set screws to hold it in place? Or do I have to drill out my receiver? How hard are the Uzi magazines to "convert" for use with this block?

Hy-tech question. This block appears to be really nice. Besides possibly needing tweaking. I would rather not take a file to a brand new 150$ mag block. Are the new ones working correctly? Being able to use unmodified Uzi mags is a great feature. Do the new ones use the square and rounded uzi mags?

Hahn question. Ok this also requires no drilling of the receiver? Does it also have set screws like the RRA block? Once again do these take the same "modified" uzi mags as the RRA block?

I plan on buying 1 modified Uzi magazine from ADCO and then trying to duplicate it on some 32 round IMI magazines. My uncle's own a big machine shop so I should have access to whatever tools it would take.

I am leaning towards the RRA block now. As long as the new one is worth a damn. Would you guys recommend this or is the hahn/hy-tech a better choice? I do not care about the bolt hold-open. I will be using RRA upper as well. If that makes any difference. More than likely I will be using a MEGA lower also.

Sorry for all the question. I did search but didn't find a lot of info like I was looking for. I did read the stickies as well. Thanks.

Quoted: I have been searching and reading for the past hour. I am really stumped on what mag block I should get. Hy-tech question. This block appears to be really nice. Besides possibly needing tweaking. I would rather not take a file to a brand new 150$ mag block. Are the new ones working correctly? Being able to use unmodified Uzi mags is a great feature. Do the new ones use the square and rounded uzi mags? "PLUG & PLAY" , as long as you not concerned with the silly bolt hold open.  The block worked as intended from day 1, just that John did not cut the mag opening to the same dimension as that of the IMI Uzi magwell found on the Uzi lower... he cut it to only accept the inexpensive surplus military mags...  the commercial IMI mags are slight larger, they fit the std Uzi firearm fine. The block sets everthing in the correct position via the mag catch, provided your lower is within reasonable spec that mag catch is in correct location...  only other issue is if the magwell depth on the lower is to spec, as some is deeper from deck to the mouth of the well, and block will not insert deep enough to allow mag catch to lock the slot on the block... My Oly was TOO deep, so I swiped the bottom of the lower a few times to allow mag catch to lock onto the block.   Some lowers have a magwell that is short,  this leaves a gap between the magwell and the block.... visual thing, some people worry about cosmetic more than simple function. Sorry for all the question. I did search but didn't find a lot of info like I was looking for. I did read the stickies as well. Thanks.

Who sells the surplus magazines? Most places I just checked only sell the IMI mags.

I bought one and never used it.
it seems it is sensitive (too tight) for certain uzi mags.
The IMI Uzi mags (with a star at the base) fit fine.

Did you ever end up setting up a 9mm AR15?

I am thinking about getting the RRA block. How much modifying do the magazines take to work in the RRA block?

Yes, I have a 9mm
I have the RR block (old style) which mounts from the bottom and is identical to the Colt unit.
I think the Han bottom inserted unit is the same. Look at the Hahn site.
The Uzi clips need to be cut (do a search - Joe Black can cut them).
I'd recommend Colt mags though more expensive they work. Uzi mags sometimes don't work perfectly.

Quoted: I am thinking about getting the RRA block. How much modifying do the magazines take to work in the RRA block?

Look at the pic above, see the mag catch notch on the block.... that needs to transpossed to the Uzi mag to duplicate that of the factroy COLT® magazine, so the mag latch will retain the magazine... now you have to worry about the block being set at the correct height for ramp and ejector placement.

A drawing can be found at the HP website that shows the mods needed to make an Uzi mag work.......look under the LIBRARY section.

Thanks for the help.

I just saw a post about a 9mm that takes sten mags. Author of the post said it works perfectly. What kind of block uses the sten magazines?

Sorry for all the questions. Just trying to find a good cost effective way to build a 9mm AR.

I love my hy-tech block. if you are going to use the same lower for both the 9mm and 5.56 upper then IMHO it is the best way to go. Why? because you just hit the mag release and it pops out and when you want to install it you just push it back in. You do have to use the right IMI mags for it but people were buying them for... 10 for $80 or so this past spring. I paid about $15 each for mine but they were worth it and with the right mags I have had only 1 FTF / FTE that I can remember in about 1500-2000 rounds, and that could have been a bad round of some cheap olympic ammo... I don't remeber ... I'm just trying to say that with the right mags, mine has functioned flawlessly. on the other hand ... for a dedicated 9mm lower I would go with the colt block and have it pinned in. just my $0.02