9MM AR-15 style Carbine Build Documented

Kramer · Feb 18, 2016

After shooting my buddy's stock ammo 5.56 AR-15 at the indoor range,
I decided that I would try a pistol round "rifle" to use indoors.
It would be much more civilized: less noise, less concussion.
I still want a real rifle version, but I figure that can wait for
better weather so I can use it outside.

I wanted to do a 9mm carbine because then I can share ammo with
my 9mm CZ-75. I like to tinker and so wanted to build this from scratch.
But a 9mm AR-15 style carbine is not nearly as easy as a stock 5.56 one.
There is less info out on the net and you need some specialized parts.
And the parts cost a lot more so it is not a cheap build.

I did a lot of research and started ordering parts. They finally all
came and I started to build the carbine. I thought I would document
the build in case anyone else came along wanting to build a 9mm carbine.
I am not finished yet, but have the major assembly that does not
require special tools done. I will continue to post as things progress.
I am a newbie--this is my first build and I just got into shooting,
so forgive me if I get some things wrong. And of course any suggestions
are very welcome.

The biggest challenge was the parts. Here is a list of all the things
I finally ended up ordering. (Note that one nice thing is that the
9mm stripped lower receiver does not require a Maryland form 77R
--at least according to 2A Sales. So I was able to get it cash-and-carry
with just a NICS check.)

Lower receiver:
Black Creek Precision EF9 Model Dedicated 9mm Lightened Forged Lower Receiver

BCG:
CMMG 9MM Bolt Carrier Group

Upper receiver:
Custom 9MM Pistol MUR (Quarter Circle 10)

Stock:
Magpul MAG470-BLK AR-15 Mil-Spec STR Carbine Stock Black (MAG470BLK)

Sights:
Green Blob Outdoors Premium Military, Mil Spec Flip Up,
Folding, Front and Rear Iron Sights Tactical Set for
Picatinny / Weaver Rails Flattop

Charging Handle:
Strike Industries High Polish Aluminum Handle w/ Extended Lock - Black

Foregrip:
Rousch Sports® Ultra Light Super Slim (seven sided keymod) "ULSV2" 12"
Keymod Mount Forend For 5.56/.223 Rifle

Stuff from Job Bob Outfitters:
ERGO AR15/M16 Grip Kit, Deluxe Tactical - 4045 - Black
JBO Lower Receiver Parts Kit WITHOUT Trigger Parts
KAK INDUSTRY 9MM AR15 Buffer 1
Kaw Valley Precision Linear Comp 9MM 1/2x36 Black Oxide
Mil Spec 6 position Stock Hardware Kit-AR15-USA Made
New Frontier Armory 16" Match Grade 9mm Barrel
YHM Crush Washer for flash suppressor
POF AR15/AR10 4.5lb Trigger w/ KNS Anti Rotation Pin

Here is a picture of all the parts ready for assembly (click for hirez image):

Kramer · Feb 18, 2016

Barrel Assembly

I began with the upper receiver. First put the barrel into the receiver.

It was a very tight fit and I could not get it in the last 1/8".

I hunted around on the web for help and noted one person said they
heated the upper receiver with a torch and then the barrel seated
properly. Thought it was worth a try so I got out my mini torch
and heated away:

Worked like a charm. After about a minute or two of heating it
slide in with a little tap:

I installed the barrel nut from my foregrip and hand tightened it.
I don't have a block to hold my upper in a vice nor a torque wrench
so I did not tighten it yet. I will go over to my friends house
later to finish that up. One issue I had is with grease lube.
For a normal AR-15 you are told to put grease on the threads before
putting the nut on. But for a 9mm build, there is no gas tube, and
it seems that is what keeps the nut from loosening. So it seems to
me that it would be better not to lube it so it will have less chance
of backing off.

I then screwed the compensator onto the muzzle. Crush washer
with cup out towards bullet travel. I just hand tightened it
at this point.

I stopped there with the barrel assembly because I cannot
install the floating foregrip until I get the barrel nut
tightened properly.

Kramer · Feb 18, 2016

The Lower Receiver

The lower receiver is from Black Creek Precision, that
seems to be not as well known as Quarter Circle 10.
It is cheaper than the QC10 one and was also available.
It looks to be very high quality. It is custom made
for 9mm colt-style magazines. Here are some pictures of it:

It came with 3 set-screws. I should have looked
at the BCP web-site, but for some reason did not think
about it. So I was not sure what they were for.
I figured out that the one with a long stem was for the
bolt release. The other 2 I did not figure out
until too late. The small one is for holding the
rear takedown pin spring in its hole. The hold is threaded
for it. It would presumably have made attaching the buffer
tube easier. The big set screw with the green tip is an
upper receiver tensioning screw. My understanding is that
it helps eliminate slop when upper is mounted to lower.
Don't think I have much slop so presumably it does not matter.

Kramer · Feb 18, 2016

Lower Assembly

My lower parts kit came with my POF trigger. I found this picture
very helpful in identifying everything (for a newbie like me):

Started with the magazine release. Initially I put the button
on backwards...the ridges are supposed to be on the outside
to give your finger some grip. I pressed the release button
down using a metal rod (arrow on image) braced on a mouse pad to easily screw
the mag catch all the way on.

Next the bolt catch assembly. The set screw BCP provided
(see arrow) instead of the roll pin made this 100% easier.
Just put the plunger and spring in the hole. Drop the bolt
release in and then screw the set screw in. Done.

I splurged on a very nice trigger assembly-the POF AR15/AR10 4.5lb Trigger.
My friend's AR-15 had the same trigger and I really liked the feel of it.
It comes with parts and decent install directions. Only tricky things
were which post goes in which hole (the posts with the raised rectangle
on the end go near the bolt catch) and turning both screws simultaneously
from each side. The retainers do not seem to fit flush with the
receiver, but I assume that is OK.

Kramer · Feb 18, 2016

Lower Continued

Trigger guard was next. One of the harder things because
of the roll pin. I am a little puzzled by the spring
loaded catch on the front attachment. The lower has
a hole right side and an indentation on the inside
of the left side. The trigger guard had the spring
loaded protrusion on one side, but nothing to catch
in the indentation on the left side. And it had small
holes on that side. Perhaps this is normal, but it
seemed wrong. I installed the guard and it seems
to be mounted firmly, so guess it is OK.

The front pivot pin is a bit challenging. I used a technique
from this video with a razor blade to hold the spring and detente
while inserting the pin (see 14 minute mark of video). It worked well.
It was a little hard for me because I could not put the receiver
in a vise; I balanced it on the buffer tube ring which was not exactly
100% stable, but it worked.

The buffer tube was also a little hard because I had no vise capability.
I weighted down the front and it stood up well enough to place all the
parts. But this is where I had a real problem. I could not get the
dumb takedown pin spring to collapse enough to get the backplate seated
ontop of the spring. I tried for 15 minutes. (I now know that the
EF9 receiver included a set screw and threads to pre-compress the
spring in position. I am still not convinced I could have gotten the set
screw in place. The spring just seemed too long even for that technique,
but maybe I am wrong on that.) So I resorted to snipping off about 1mm
of the spring. Maybe that will cause problems in the future with my
takedown pin, but it seems to be plenty firm for now.

I did not have the tool to tighten the castle nut, so I left it hand tight for now.
I will take it over to a friend who has the tool to complete the assembly later.

Kramer · Feb 18, 2016

Lower - Safety, Grip, Buffer, Stock

I installed the safety, safety detent and spring.
This is where I missed another of the special parts
that came with the EF9 lower--the upper receiver tensioning screw.
See that threaded hole behind the grip mount: that is where
I should have put that screw. I can go ahead and take the grip
off and install it later if I think it is really needed.

I put the grip on and started tightening the socket head
grip screw and it got super tight before the grip was fixed
in place. I took it back apart and tried threading just the
screw in with grip off. The threads were just very tight.
So I put some lithium grease in the hole and tried again.
This time I was able to tighten it sufficiently.
The "ergo" grip has a nice rubbery feel. It is a lot bigger
than a standard grip. Have to try it out to see if I like it
being so big. If you had a small hand I would think it might
just be too big.

I got a buffer especially for a 9mm carbine. The spring
is just a normal spring. My research gave no clear indication
of whether a special spring would be necessary. I figure I can
change it easily enough in the future. There was also many
differing opinions on whether to lube the buffer and spring.
I finally just used some teflon lube on them. Trivial to install it.

The Magpull stock was a pain to install. They give this plastic
dummy round that is supposed to lever the retaining pin down
so you can get it over the buffer tube (per their included
instructions). This did not work at all and I hit the net.
Found this video that explains how to really do it:
use a flat head screw driver. After that it was easy. Don't understand
why Magpull do not fix their instructions and just forget about the
dummy round.

At this point everything that I could assemble was pretty much done.
Next attaching the upper to the lower!

Kramer · Feb 18, 2016

Final Assembly

Although I still had things that had to be tightened up
and installed (foregrip), I really wanted to see how things
looked and functioned at this point. So I installed the BCG
and charging handle and attached the upper to the lower.
Tried out all the controls (safety, charging handle, bolt catch).
Only issue was the bolt catch. To make it catch I have to press
on the lower part of it. But I do not have a magazine yet to
install--I have a memory that it changes things with a mag in it.
I slid the foregrip on to just see what it looks like, and I like it!

Update:
I got impatient to mount the foregrip and had an idea
for a wooden jig to hold the upper receiver. I took
a piece of 1x4 and drilled out holes for the pin
blocks on the receiver. Then __gently__ clamped it
and used an adjustable wrench to tighten the barrel nut.
Took a bit of fiddling to get the barrel nut right so
that the foregrip lined up correctly. Tried some shims
that came with the foregrip, but 1-3 of them would not work.
Finally loosened and tightened the nut 3 or 4 times and
was able to get it lined up. Also tightened the compensator
at the same time. The jig worked really well.

I then mounted the sights. They are pretty cheap ones
I found on amazon, but look to be well made. I am a little
puzzled about elevation adjustment. It looks like the front
sight has the adjustment but would require some type of tool
that did not come with the sights. If anyone has any ideas
I would be glad for help.

The only thing remaining (I think) is to tighten the castle nut.
Can't think of how to do that without the proper tool.
I greased the charging handle
and lubed up the bolt with some grease and mobile 1 oil.
Exercised the bolt many times and it seems good to go.

I will update this post once I get it finished and range tested.

Kramer · Feb 19, 2016

Finish and Range Testing

I managed to get the rifle finished and range tested.
Brought the carbine over to a friend who had a tool
to tighten the castle nut on the buffer tube. He also
had a punch to stake the castle nut.

Then it was off to the range. After a way too long wait
for a lane, setup sitting down and loaded one round via
the magazine. Set the target to 7 yards and pop, center
of target, bolt is open. Yes! Two rounds loaded into magazine.
Pop, pop. Two center of target. Second round fed fine.
Here are the first 3 shots:

Proceeded to check the sites out at longer range and
shoot an entire magazine (obtained out of state, 32 rounds).
No problems. Very accurate at limit of indoor range (25 yards).
Gun is a pleasure to shoot. It is very light and easy to handle.
Put 150 rounds through it with nary a misfire.
Very happy! Only negative: loading those colt magazines by hand
is a total nightmare. Have now bought (in the mail) a maglula
designed for this magazine--video I saw makes it look easy.
Let us hope it is as easy as it looks.

outrider58 · Feb 19, 2016

Alphabrew · Feb 19, 2016

Looks good. 9mm ARs are super fun.

I've have/built two 9mm ARs, one in rifle config and one in pistol config. I used the POF trigger in both, it's pretty sweet. I am also using the Battle Arms SS selector. With that and the POF trigger I've noticed I can put the gun on safe even when the hammer is not in the cocked position. One build is a New Frontier glock lower and the other is a Spartan glock lower from JoeBob. The JoeBob one was under $125 shipped during a sale, so I FO'd. I wanted the New Frontier LRBHO upper but got tired of waiting for it.

Here's the rifle, no pics handy of the pistol

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slowpoke · Feb 19, 2016

Nice work Kramer and Alpha. I think the 9mm AR Pistol is desperately looking for a friend of the carbine persuasion.

Kramer · Feb 19, 2016

Thanks outrider. That is quite a foregrip Alphabrew, looks good!
Can't wait to finish mine and try it out.
-Kramer

Gambler · Feb 20, 2016

Nice write up!

dontpanic · Feb 20, 2016

Nice looking rifle. You will have a lot of fun with it. Go up to PA and get some 30rd mags for it.

I used the POF trigger in my 9mm AR as well. Good trigger. I built mine as a pistol and submitted a form 1 to SBR it. I should get my stamp soon.

Kramer · Feb 20, 2016

dontpanic said:
Nice looking rifle. You will have a lot of fun with it. Go up to PA and get some 30rd mags for it.

I used the POF trigger in my 9mm AR as well. Good trigger. I built mine as a pistol and submitted a form 1 to SBR it. I should get my stamp soon.

Thanks!

Yeah, already planning a PA trip. The whole tax stamp thing was a bit too much for me and I was looking to practice rifle style indoors.
-Kramer

rouchna · Feb 20, 2016

Nice work. I built my own as well. It is now a suppressed SBR.

Kramer · Feb 20, 2016

Very nice rouchna. What lower is that?
-Kramer

Suleiman · Feb 21, 2016

Looks fun. Reading through your experience sounded very similar to my first AR build.
The feeling of accomplishment when you send the first few rounds down range is unmatched!

rouchna · Feb 21, 2016

Kramer said:
Very nice rouchna. What lower is that?
-Kramer

Thank you! It's a Quarter Circle 10 lower.

Jasonshooter · Feb 21, 2016

Has anyone else had trouble with their bolt catch bending ? This seems to be a real problem with the 9mm builds , I've done all I could to limit bolt travel and switched springs and buffers ... Any of you guys had this issue ?

9MM AR-15 style Carbine Build Documented

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