OK, let us assume that I am bored.

If I want to take a perfectly functioning AR15 variant SBR that is chambered for 5.56 and make it 9mm what do I have to do.

1.  Go to the RRA web site and order a 9mm upper complete with BCG and charging handle...

2.  ?????

Then what.  Mags???  Something that goes in the mag well??  different buffer and spring??

For the sake of discussion pretend that I know how to build a AR15 in 5.56 from a stripped lower.  Pretend that I already have the form 1 approved.  

BUT other than owning too many 9mm pistols I know NOTHING about AR15 SBRs in 9mm

I also own some Tec 9/AB10 mags if they could play a roll in this.

Thank in advance guys.

1. Yes

2. You will need a magwell block that accepts the 9mm mags. You will need 9mm mags, you will need to make sure you have a rounded hammer (not the notched hammer) and you will need a 9mm buffer. I think that should do it..... oh and lots of ammo. =)

OK, is there a brand name of mags that are high quality...something like MagPul?
Is there more that one kind of mag well "thingy" (block) or are they all the same useing the same mag?

you can ramp your bolt and use regular hammer. Also the metalform are considered the best mags. $40

OK guys...

Thanks for the help.  I found all the stuff at RRA and Brownells.  Had no idea that the magwell block would be so expensive.  I might just go with a didicated RRA 9mm lower and do another Form 1.

Food for thought.

Just Sayin!

I've been looking into doing this as well. I believe spikes makes a good magwell block. I have no experience with it, but I am leaning towards it.

ETA link

http://www.aimsurplus.com/product.aspx?item=XSTSM9B001&name=Spikes+Tactical+Enhanced+9mm+Magazine+Block&groupid=53

I'm currently talking myself into a 9mm suppressed SBR from DDLES. At the moment I can't decide if I want to use Glock or Metalform mags.

Not to hijack, but as anyone tried out their Glock mag lower?

Thanks for the link.

I like spikes stuff.  That is probably the one I would go with if I decide to do the block v the dedicated RRA lower.

This project just ran up the cost more than I wanted to spend just to break the boredom.

Wow, that looks like the way to go.

Anyone done business with them?

It looks like you can have them engraved before shipping.  

Can I assume these ship as Title I lowers and do not become Title II until the form 1 is approved and the short upper is installed.  I hate doing Form 4s

Yep they would transfer as 'other' on your 4473.

You can also get a VM Hytech mag block that uses unmodified Uzi mags if you already have any investment in that.  They work on any standard AR lower.