9mm AR FAQ:
How to build a 9mm AR
To create a 9mm AR15 you need a few different parts than a normal 5.56 version. The most common 9mm AR setup on the market today is the Colt pattern and this faq will be discussing primarily the colt pattern 9mm AR15. To create one you will need a 9mm barrel, A 9mm bolt assembly, and a way to hold a 9mm magazine (a magblock or dedicated lower), a heavier buffer and smooth faced hammer.
Starting a 9mm build from a stripped .223 lower.
There are many mag blocks and now dedicated 9mm lowers that work with the colt system. If you are going to use a traditional .223 sized magwell AR15 stripped lower you will need a magblock to be able to hold 9mm magazines.

Magblocks
The major magblock manufacturers are Hahn and RRA (spikes makes a version of the RRA block). These are one piece blocks that are ether installed from the top or the bottom of the magwell. The RRA style block is a bottom loader and has a tension mechanism that
you tighten to snug it into the magwell. All of these blocks are good to
go. There is very little difference in the function of all of these
blocks except that the bottom loaders allow for some vertical
adjustment of the block.
Hahn offers a top loading, bottom loading as well as a dedicated block  (you need to remove the bolt catch to install it).








                           
Both the hahn bottom loader and dedicated block will have last round bolt hold open using a standard .223 bolt catch. The top loader requires a long finger 9mm bolt catch to engage last round bolt hold open. This dedicated 9mm bolt catch does not work with a .223 upper. You have a choice with a top loader, you can ether use the 9mm bolt catch and have BHO and it becomes a dedicated 9mm lower, or use a .223 bolt catch and have no BHO (but a swappable block without tools).

The RRA block (and other bottom loading blocks) have an allen head socket in the bottom of the block that is tightened to hold the block securely in the lower. This allows the user some adjustment over the height at which the block sits in the lower and this adjustment can be used to help your 9mm AR function with Cproducts mags. Cproducts recommends that you will need to adjust the magazine block .015-.020 lower to function properly with a Rock River upper.








The VMHytec mag block is special in that it will allow a user to run unmodified uzi mags. This block has a different manual of arms than a traditional AR because the block has the mag release built into it. The traditional AR mag release button will drop the magblock out of the lower.  This block is a good option for an AR that would be switched often to .223 or if you had a lot of uzi mags on hand (uzi's are probably the cheapest preban mags available for those behind enemy lines). This block does not have a functioning last shot bolt hold open.

Cproducts currently offers an inexpensive 9mm magblock.  There have been reports of inconsistent function.   YMMV
The original style colt magblock was a two piece unit. Most current magblocks are one piece designs. With a two piece block drilling and pinning the block into the lower was sometimes necessary.
There is a company SNS industries that still offers a two piece magblock. This block will allow you to run Sten mags. This block has a different ramp design because sten mags are centerfeed rather than doublefeed like the uzi/colt mag. If you have a lot of Sten mags this may be an option for you.
There are older blocks that are made by ASA, Crossfire and others that are no longer being sold.
Magazines
For the colt system there are a few different magazines that are available.
The gold standard are magazines made by the Metalform Corporation. They produced the original mags for the colt SMG's and their mags are known to function usually 100% with any quality magblock. The Metalforms can be ordered directly from the company or from a couple of vendors that resell them.

Uzi mags/drums will work in a colt style 9mm. Unmodified Uzi mags can only be used in the VM Hytec block.

To use uzi mags in all other blocks (Hahn, RRA etc) they will need to have an AR mag catch slot milled into the side and the back of the mag relieved.  Uzi mags will not activate last shot bolt hold open but they are currently the cheapest preban mag for those behind enemy lines.

The uzi mag modification specs:







Cproducts makes a 9mm mag that has been somewhat hit or miss. Most people can get them to run if they setup their magblocks at a correct height for the mag (this requires an adjustable bottom loading block). They are a nice low cost metal mag if they run in your gun and quality seems to be improving with time.
Promag makes an inexpensive plastic mag. They tend to bulge when loaded and some have experienced function issues. YMMV.
There are also beta C mags available for when you need to have 100rds  of 9mm on tap. Not sure if they have LRBHO but after 100 rounds unless you are fully auto I don't know if it matters.
Hammers and Triggers
Choosing a correct hammer is important to proper functioning of the 9mm AR15.
The best all around hammer is one like the DPMS Hammer below. The face of this hammer is smooth allowing it to function correctly with a .223, 9mm or rimfire bolt/upper. This hammer will reset in a short amount of bolt travel so some 9mm owners may want to have their bolt ramped to work with this hammer.

The RRA style hammers below have notches on the front that will jam the 9mm bolt. You will want to avoid this type of hammer.

There are dedicated 9mm hammers that are made to decrease the impact that the 9mm bolt places on the hammer and pins. Due to 9mm bolt design hammers are reset in only 1/4-1/2" of bolt travel, which puts a
stress on both the hammer and the hammer pins especially in full auto guns. 9mm hammers will work with a non-ramped 9mm bolt and help ease the impact of the bolt on the hammer. They should also work with a ramped bolt.

Buffers:
Most 9mm buffers are 5oz and up. You need to tune the buffer weight to the bullets that you shoot. Heavier bullets will require a heavier buffer.  Also if you are running a suppressor a heavier buffer will keep gases going out the barrel instead of the ejection port.
If you are using a A1 or A2 rifle length buffer tube, stick to the rifle buffer since it weighs around 5oz and you can add weight to it if necessary. There is an RRA spacer that allows you to run a carbine buffer in a rifle length buffer tube. But it is easier to stick with a traditional rifle buffer.
If you are using a carbine length buffer tube you can start with a lighter buffer but most will start with a 5.6~ ounce 9mm carbine buffer.  
There are 9mm specific (dedicated)  buffers available that are longer than a traditional carbine buffer. This limits the rearward travel of the buffer. People switch to these buffers if they are breaking bolt catches using a heavy carbine length buffer. You can also place a block in your buffer tube to limit rearward travel. People will use quarters, a piece of dowel or a commercial block for this. You can not use these buffer tube spacers with the longer (spikes or slash) buffers. Both the longer buffer and/or buffer tube block will not allow you to use a .223 upper on the lower without swapping these parts out.
You can run a wolff extra power buffer spring in a 9mm but a regular carbine spring will work. The heavier spring will help keeping the bolt closed when using heavier bullets of hotter loads.
Extras:
Some people including me have added KNS pins to our 9mm builds. The blowback bolt is rougher on the fire control group and cause the wear of the FCG pins and the lower itself. The egging out of pin holes in a lower is caused by a combination of the force on the pins and the fact that the standard pins can
rotate.  The more the pins rotate and the harder they are pushed into the
lower, the more quickly they will tear through the anodizing and cause
the pin holes to go out of round.  This can be resolved by simply using KNS
anti-rotation pins. This is especially important in a full auto gun, preban or an SBR where you want to make sure that your expensive lower stays in perfect spec.  

Starting with a dedicated lower:

With a dedicated lower your magblock is built directly into the lower, this precludes the use of the lower with .223.
CMMG, RRA, DDLES and Lone wolf among others? offer dedicated lowers. The CMMG, RRA and DDLES work with colt compatible mags. The Lone wolf lowers are made to work with Glock mags. but machine work needs to be done on a colt pattern bolt so that it works with the centerfeed glock mags.
With a dedicated stripped lower you will still have to follow the build information above selecting a correct buffer, hammer and mags.  You can just forget about having to choose a magblock.




Now on to the upper.
upper receiver:
You can use any standard ar15 upper receiver for a 9mm build. RRA makes a pair of slickside uppers that are made for 9mm (no gas tube hole). Spikes also has a custom upper that has a built in gas deflector as well but you can use any upper. Some people prefer to use uppers that don't have a forward assist since it is not needed on the 9mm.
Bolt:
The 9mm takes a completely different bolt assembly than a .223. It has a weighted insert at the back which can be removed or changed to alter the overall weight but it doesn't separate into bolt and carrier like a .223 bolt. It also doesn't have any locking lugs due to the direct blowback operation of the gun.



A common modification to a 9mm bolt is bolt ramping. The short ramp on the bottom of a 9mm bolt causes the hammer to reset in a very short amount of bolt travel. The bolt contacts the hammer low on the face and this may cause the rotation and/or breakage of the
hammer pins and eventually can cause an egging out of the receiver pin holes, especially with full auto use.

This extra stress becomes an issue if you have an
expensive preban, SBR or M16 lower that you need to preserve. The
egging and wear can be slowed or eliminated by using stronger KNS anti rotation pins, a 9mm hammer
and/or by ramping the 9mm bolt.


Ramping was not done on the original colt 9mm ar's. Colt countered the extra stresses by upgrading the FCG pins to stainless steel and then later offering ramped bolts in their 9mm guns.  (is this info correct?)
It was recognized that the ramp on the bottom of the 9mm bolt was much shorter than a ramp on a .223 bolt so some gunsmiths decided to mimic the ramp angle and length of the .223 on a 9mm bolt. This ramp allows the hammer to reset more smoothly and lessens the stress on the pins and the lower receiver.

There is some discussion on the correct angle of ramp and it seems that Adco does a steeper ramp than most. They have said that this steeper ramp works with a greater number of hammers.  Member RyanHass made this tutorial on diy bolt ramping 9mm_bolt_ramping.pdf
Here is a picture of an Adco ramped bolt

Barrel:

9mm barrels are mostly not chrome lined (colts are the exception) and have 1:10 twist. Due to the blowback operated action there is no gas hole in the barrel. Some barrels will come with a pin to align the barrel to an upper receiver but some will not. The chamber of a 9mm barrel will stick farther inside an upper receiver than a .223 barrel.  Noveske does a limited run of 9mm polygonal rifled barrels from time to time.

-muzzle devices and threading

9mm barrels are traditionally threaded 1/2x36 to keep people from using .223 1/2 x 28 muzzle devices on 9mm barrels. There are specific 9mm flash hiders made with a larger opening for the 9mm round and in 1/2x36 pitch. If you have your barrel cut down and re-threaded to 1/2x28 or have a 9mm barrel that is 1/2x28 you can take a .223 muzzle device and bore it out to fit a 9mm bullet.
That's all I got for now

Tell me what I need to add. I didn't add the oly stuff or many pictures yet.
 

What has proven to cause "egging out"?  Ramped bolts or non-ramped bolts?

What are the advantages and disadvantages of each bolt type?

Not a bad start, but it sort of reads as if 9mm AR's are a relatively new phenomenon as you left out all the historical info...

Magblocks - you didn't really cover the regular vs. 9mm bolt catch thing that many people don't fully understand.  You didn't go into integrated lowers at all, nor did you mention all the other makers of blocks out there (past and present) or the Colt 1 and 2 piece offerings.

Mags - Uzi mags also need the back relieved.  Don't forget about the betas...

Hammers - DPMS/M16 hammers work just fine with ramped or non-ramped bolts.

Buffers - blowbacks are all about tuning the weight of the bolt/buffer to the load you are shooting.  There is no hard and fast rule here.  Some guns will run std. pressure ammo just fine with a std. carbine buffer, even though the 9mm buffer is ~5 oz.  You may want to also note the spacer/quarter trick instead of dropping big money on a specialty long buffer...  You may have to touch on the RRA "spacer" that is for using a carbine buffer in a rifle tube as some people get confused by it and think it is for a carbine tube...  Ramping the bolt makes it easier for the bolt to move rearward (as does using a reduced power hammer spring), so it is usually necessary to run a heavier specialty buffers with ramped bolts to help keep the bolt from moving back too quickly after firing...

Bolt - technically, it is not all one-piece - it has a weighted insert at the back which can be removed or changed to alter the overall weight.  The egging out of pin holes isn't really caused by the bolt being ramped or not ramped, it is caused by a combination o
f the force on the pins and the fact that the standard pins can rotate.  The more they rotate and the harder they are pushed into the lower, the more quickly they will ear through the anodizing and cause the holes to go out of round.  This can be resolved by simply using KNS anti-rotation pins - ramping is not "necessary"...  You may want to touch on the replacement of the extractor roll/tension pin as that is a popular mod.

If you really want to do it up right, you are going to need to scrounge a lot of pics.  You will also want to mention the LWD Glock lowers also.  You will also want to probably so up a basic set up and troubleshooting section also - cover things like how to adjust the ejector and how to do a basic function check when assembling a new 9mm AR...  You may want to put all the links to Hahn, M60Joe, Spikes, etc... in one place also for reference.  Oh, and you will probably want to grab an archived copy of the MD AR shooters sighting in instructions as that seems liek a popular piece that many people don't know how to find via the internet wayback machine...

Great start.  I agree that lots of pictures are in order.  Which ones?  Pics of the different blocks (I don't think you mentioned VM-Hytech).  Pics of different kinds of mags (just general pics; a catalog of the different kids of CProducts mags (so far) could be its own huge FAQ).  Pics of the bolt, especially comparing ramped and un-ramped.  A comparison pic of the depricated 9mm hammer.  Pictures of the different bolt catches-especially when noting which blocks - and magazines! - they go with.  And all important, the ever reliable SBR7_11's ejector pictures.  Pictures of different buffers, particularly those with identification markings or distinctive shapes.

That's all I an think of at the moment.  I'm sure we can all start harvesting picture URLs for discussion, and if SBR7_11 chimes in with his pics we'll be in business.

magazines: promag also manufactures steel bodied magazines. since lone wolf? is doing the glock lowers, maybe mention of glock compatible mags would be worth mention. also unmodified uzi mags for the vmhytech blocks

hammers: old colt style, new colt style (actual M16 hammer), and RRA 9mm hammer

barrels: Colt is the only chromelined barrel I know of. I would also include information on twist, who uses which twist and what the twist rate will do to the ammo you are using. Also put in some info on which barrels are threaded in which pitch and barrel lengths.

buffers: you could also talk about the "buffer spacers" that RRA, spikes, and Colt are currently using/offering.

upper: some companies offer dedicated 9mm uppers which do not have gastube holes and some even do not have the notch for the cam in the bcg. Manufacturers are but not limited to ASA, Nodak, Colt, RRA, Spikes, and Vltor...

magblocks: include Cproducts and the fact that Colt blocks are pinned perfection. Colt blocks are somewhat hard to find, but out there. m60joe can drills and pins colt magblocks. don't forget about the VMHytech uzi block

Also, inlcude a section on lowers including 9mm marked lowers and 9mm dedicated lowers. nodak offers 9mm marked lowers with an open magwell. dedicated lowers include: Colt, CMMG, DDLES, RRA and lone wolf?

I would also include a section of complete AR style firearms in 9mm. CMMG, Spikes, Colt, RRA, YHM

Don't forget about 9mm suppressors...

Lastly I would include a section on muzzle devices according to thread pitch. RRA, Colt, Spikes, YHM, and others offer flash hiders/brakes.

Great! I will work on it more tonight. I was having a lot of trouble thinking about how to organize it since there are so many variations.



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are you allowed to add sources for the parts?

for example: where is the cheapest place to get these 9mm stripped uppers?

I am wondering about that too.  I was/am trying to keep it as brand neutral as possible. I don't think it should be current pricing since that would change over time.

Melante I need some suppressor info I don't know a thing about them. We can't have them here.   I do know that people load the 147s to be subsonic so it will be extra quiet with the can.

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Who has the least expensive X at the current moment WILL change in weeks, months, years.  That data would either need to be updated or it would become completely obsolete very quickly.

Yeah I wasn't so much worried about price but advocating for one brand over another. Like how much attention do you give to Spikes vs RRA (who have been around longer etc) I wanted to stick to major technical areas and less to specific manufactures.  There is a lot of info in the previous faq like SNS mag blocks for instance that may or may not be still available etc. Like m60 Joe is he still doing stuff? I dunno if that is as important as knowing that you may want to have a ramped bolt. Then the user can search for a service that does it.





 

Kevin is the long bolt catch only used on the top loading Hahn?  or is there another block that I am missing. Can you explain the colt 1 and 2 piece blocks I have never seen them. Were the colt 2 pieces pinned in factory or were they setscrewed and people pinned them to make them more stable.





 

Dont over complicate the thing...

Basically we are taking the plain old everyday AR-15 and shooting 9mm... so we just need an AR-15 upper and lower assembled as such,  something to fill the extra space of the 556 magwell to hold a 9mm mag in position, a 9mm barrel to mount in the upper, a 9mm bolt assembly,  magazine to hold 9mm ammo.

Leave out all the "I am going to build with",  leave the magwell info to the COLT pattern 1 piece (as SPIKES, HAHN, CROSSFIRE, COLT, RRA), and other clones all serve the same purpose, the original 2 piece as produced by COLT when they brought out the 9MM Submachine Gun by simply setting their 9mm upper on the M16 lower and filling the magwell with 2 piece block set.

Magazines ––  leave it to the COLT style (Metalform, C-Product, plastic ProMag), and the Uzi mag with notch cut to dupe that found on the COLT mags

Along with the magwell block, the VM Hy-Tech block to use plain old everyday Uzi mags, no need to cut COLT type notch, good choice for the Uzi owner.

Buffer ––  stick to the "use rifle buffer in rifle stock",, DO NOT install CAR buffer in rifle stock with magical adapter spacers, Rifle buffer comes in at 5.2oz, dump the guts, and fit a brass dowel, that'll get approx 7oz... and if using the CAR type stock, use CAR type buffer of at least 5oz, such as the "9mm" buffer @ 5.5oz.

There are many options for heavier if wanting to go suppressed to cut debris out the eject port.

Trigger group, std AR-15 trigger group, use a neutered M16 hammer or DPMS LR-33 hammer... no real world need for  COLT style 9mm hammer

Upper, std AR-15 upper, just need something to set on top of the AR-15 lower, and hold 9mm barrel in place, and provide runway for bolt to move back and forth

In the end, don't over complicate it.


Pictures, I have some pictures, or I can take some, I just have a simple 9mm using the Hy-Tech block

I am going to add pictures later. What I want to do is grab all the pictures I can and them host them on a google account so that they will be there for longevity. I will go back after I have it mostly written up and add the pics. So I may need them in a couple days.






?? I thought it would be easier to explain if it was written like a buildup from a stripped lower and from a dedicated lower.
Thanks for the info!

Did SNS redesign their magblock?

I've got 3 that I bought a few years ago, and they were made for use only with Sten mags, but could be switched to work with a colt style upper by adding a RRA ejector, or work with an Oly upper by leaving the RRA ejector off.  

My bad I thought they could be used with both so they only can be used with sten mags? makes sense. I read somewhere that it would be easy to make a ramp that would work with centerfeed and double feed mags so I thought that is what they did. They hardly ever come up on the forum so I didn't have a clue



 

I don't know how well it would work if the ramp was made to work with either.  The reason I have 3 of their blocks is that I bought one, then realized it would be possible to modify it to work with other mags by spending several lunch breaks with a vise, die grinder, dremel, and files. One of them now works with double feed mags in another caliber, but I probably spent as much time (maybe more) reshaping the feed ramp, as I did reshaping the block to fit the mag.

ETA: The SNS block uses the AR's mag catch, so the Sten mags have to be notched for the mag catch.

Bravo makes an insane Mil-spec 9mm barrel.  10.5 inches.
Chrome lined.

http://www.bravocompanyusa.com/BCM-9mm-SMG-Barrel-Stripped-10-p/bcm%20barrel%20ff%209mm%2010.htm

I believe that barrel is NOS colt smg barrels. I don't think they are new production from bcm. I would hope they would be able to make a barrel without a spacer. Colt had a run of 9mm barrels that required a spacer that could be found at numrich for cheap.

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For those of you that are having problems with the bolt catch not holding back on the last round/empty magazine using Cproducts 9mm magazines....Look here.
...I hope this is okay to post (not my thread but hope it helps). I did the same mods on my own to mine before I came across this post.

The BCM barrels are not NOS Colt SMG barrels.

What BCM shows and advertises is not what my 10.5" Colt SMG barrel looks like.

I would think that simply suggesting that Cproducts magblocks have had reliability issues is better than saying: "It hasn't been proven to work reliably so it is best to pass on it."

I do not own or have experience with the Cprod. magblocks and I have read about reliability issues, but I don't think Cproducts would enjoy having their product slandered in a FAQ. Probably best to edit that part if it is to be included in a FAQ.

Do you think BCM is their own run? I can't believe they would make a barrel that needs a spacer.
I will change my wording about the cproducts block.

BCM 10" Barrel

That's definitely a different profile.  Has Colt used that same profile forever though?  Not arguing, just asking...

Yeah it looks totally different. interesting. I am still wondering what is up with the spacer.



 

You would think that if cutting barrel from blank with all kinds of extra outside diameter that they would have cut the flange correct the first time...

Note the supplied COLT marked barrel above, has a thicker OD behind the sight base, and the BCM barrel is tapered, maybe they cut the OD of the barrel to lighten it (and remove  previous marks)

Too funny that a number of yr ago the "barrel nut wont hold my barrel  from E-Gunparts to my upper" came along... now BCM comes down the pike with barrels and shims so the barrel nut will hold barrel

ohhh i think you are on to something. they took those barrels bought them all cut and turned them down. Interesting. there is just something strange about the spacer.



 

The SMG barrel above was made 1/00. The 16" Colt barrel below was made in '93. I also have a new 6450 and will take pics of the barrel later on...

Colt Sporter 1993


COLT SMG barrel 2000

The '93 to '00 difference is "forever" enough for me.  That is apparently Colt's profile.  I really think the "they turned down thicker barrels" theory is pretty strong right now.

My 3 Colt 9mm barrels spanning ~20 years. 1993 16", 2000 10.5", 2009 16"
The design is the same on all 3.

Can someone read the bolt ramping section and let me know if this is ok.