9mm sbr AR platform

[Jeremiah]

A friend of mine is looking to build a 9mm SBR on an Ar reciever, He is looking for advice on Uppers. Who makes them in 9mm , what type of Accuracy do they get out of them? and any issues he should be aware of with building a this type of rifle?

 

[bigcraig]

RRA,J&T are the only folks I buy 9mm AR components from.

I consider my 9mm AR SBR a 100 yard gun. Before I starting having issues with my Eotech, I could hit a standard steel pepper popper at that distance easily.

No issues, as they will run fine right out of the box really. There are some slight mods that can be done for reliability sake, but if it runs fine out of the box, don't mess with it.

 

[Jeremiah]

thanks

 

[melensdad]

Also, Colt and Olympic Arms make 9mm AR components. Oly offers 2 different versions, one uses Sten magazines the other uses standard Glock magazines. I've heard good things about RRA, Colt and Oly 9mm ARs. I believe all are recoil operated, I have an Oly and know it is recoil operated. That means there is no gas tube. The 9mm ARs also use a different weight recoil spring/buffer assembly.

I agree with bigcraig, 100 yards is about it for any practical shooting.

 

[Jeremiah]

I am glad I'm not trying to build this, because If I tcould build one to run sten mags, then I would have a greater desire to buy a Sten

 

[techres]

Let me add a couple of questions:

1. BigCraig, why only RRA & J&T?

2. I know these run great with ball (NFA day is the only reason I consider one), but as a self defense weapon - are they reliable with HP/JHP ammo?

3. Is there much effective differences in terminal power and accuracy between the 5.5"/7"/10.5"/11.5" barrels? Seems like the shorter is the only option if you are thinking of suppressors, but if an A2 KISS SBR is what you want is there any "real" bonus in the longer barrels?

Thanks!

 

[shooter521]

I believe all are recoil operated, I have an Oly and know it is recoil operated.

Blowback operated, not recoil.

I know these run great with ball (NFA day is the only reason I consider one), but as a self defense weapon - are they reliable with HP/JHP ammo?

Mine is. I've run both standard pressure and +P hollowpoints in a variety of brands/styles without any problem.

if an A2 KISS SBR is what you want is there any "real" bonus in the longer barrels?

Velocity. That's why I opted for a 9.5" barrel (which I'll run suppressed anyway) over a 5". If I want to shoot 9mm out of a 5" barrel, I've got a Glock 34. And longer sight radius, as well.

 

[absrio]

My RRA 10.5" puts a the WWB 115grn out at 1300fps. I have some 147grn XTP's loaded up I want to try to see how it feeds HP but I do not see a problem. Mine hates UMC 250rd bulk pack. Out of a 32 round mag I will have FTE issues on about 7 rounds or so. I love shooting the 9mm ar pistol almost more so than the 223. I sighted mine in at 25 yards I have yet to get much further out than that.

 

[in812]

I have a few questions i have considered building a 9mm sbr also lets start with the mags which style to go with and why ?
1) colt ar
2) uzi modified
3) sten
are their any other options ? anyone had any problems ? I'm thinking the uzi mags because i can machine them and they cost less but i have a few sten mags so ?

mag well adapter ? their are a lot of mfg's out there what have you had experience with ? I've been looking at the hahn-precision


bolts ? are all the 9mm bolts interchangeable ? it looks like the sten mag conversion would have the mag forward can you use a ar15 bolt carrier or is the 9mm BC special ?

hammers ? can you modify std ar hammer or use a std ar hammer ?

buffers and springs can you use a H2 buffer and std spring ? or ?

finally Barrel's I thinking 10 1/4 or 11 1/2 length wanting to go with a SS barrel
who mfg's SS ar 9mm bbls in the shorter lengths ? what twist ? all I've found in SS is 16"

One last thing does anyone make a side cocker upper for the ar 9mm setup or maybe a hand guard with cocking rod setup through the gas tube hole ?

 

[melensdad]

Blowback operated, not recoil.

Thank you. And absolutely correct. Must not have had my coffee yesterday when I posted that.

I have a few questions i have considered building a 9mm sbr also lets start with the mags which style to go with and why ?
1) colt ar
2) uzi modified
3) sten
are their any other options ? anyone had any problems ? I'm thinking the uzi mags because i can machine them and they cost less but i have a few sten mags so ?

I went with Sten because with a mag well adapter block I can use totally unmodified magazines. Nothing better than keeping the magazines stock for gun 1 and being able to use them in gun 2.

 

[shooter521]

lets start with the mags which style to go with and why ?

Colt (or the Metalform equivalent thereof). Reasons are several-fold, but the biggest one has nothing to do with the mag, but rather the system that uses it:

1) The Colt-style 9mm carbine is a proven system, with bolts, receivers, barrels and mag blocks available from a variety of manufacturers (Colt, RRA, Garrison, Hahn, TROS, Bravo Co, etc). The Olympic 9mm carbine is a proprietary design; its components are not interchangeable with the Colt style, and no other vendors are making Oly-compatible parts, AFAIK. Further, Oly no longer lists a STEN-compatible 9mm carbine on their website; they seem to have put all their eggs in the Glock magazine basket with regard to that caliber.

There have been a few guys who have modified Colt-style 9mm carbines to accept STEN mags, but from what I understand, this is a major undertaking.

Regarding the mags themselves:

2) Colt-style mags are made for the commercial (and LE) market, and are new-production. STEN mags are 50-60 year old military surplus, and condition can vary widely. Additionally, as with all surplus, supplies are going down and prices are going up; STEN mags aren't the cheap, plentiful solution they once were.

3) Colt-style mags are smaller and lighter, which makes them easier to carry (not a big deal if the gun is just a range toy).

4) Colt-style mags activate the gun's last-round bolt hold open, making the manual of arms pretty much identical to your .223 carbines.

I'm thinking the uzi mags because i can machine them and they cost less

Uzi mags will work fine in your Colt-pattern carbine, IF 1) you properly machine the bolt clearance in the back and the mag catch cutout in the side to match a Colt mag, and 2) you don't want/need the last round hold-open feature.

I had a machinist friend of mine convert a number of UZI mags for me back in the day. Biggest thing is to start with good mags (IMI, FN or South African) to begin with; even then there was quite a bit of variance in fit from mag to mag. I did like having several capacities available (20, 25 and 32rd), and the mags were built like damn tanks. But again, with prices going up and supplies going down, UZI mags may or may not be a cost-effective solution, especially when you factor in the time and effort required to machine them. You can get C-Products mags, which are essentially Colt clones, for less than $20 a pop these days. Metalform mags (which Colt used as OEM until just recently) aren't much more expensive at around $30.

mag well adapter ? their are a lot of mfg's out there what have you had experience with ? I've been looking at the hahn-precision

Colt, Hahn or RRA would all do fine. The mag block in mine is a two-piece design from JRW Sports. It's about 10 years old, and dates from the dark days before RRA and everybody else jumped in and opened up the 9mm AR market. It's ugly, but it works. Ameetec Arms makes a mag block that accepts un-modified UZI mags. It looks a little clunky (extends out the bottom of the magwell) and has its own separate mag release button, but seems to work well if you don't want to machine your mags or pony up for Colts (pun intended).

are all the 9mm bolts interchangeable ? it looks like the sten mag conversion would have the mag forward can you use a ar15 bolt carrier or is the 9mm BC special ?

The 9mm bolt and carrier, regardless of whether you're talking the Colt or Oly system, are unique to 9mm and not compatible with .223. As previously mentioned, the Colt-style and Oly 9mm bolts are not compatible with each other. All of the Colt-style 9mm bolts (Colt, RRA, Garrison) should be interchangeable.

hammers ? can you modify std ar hammer or use a std ar hammer ?

Speaking strictly about the Colt-pattern guns here: you can modify a standard .223 hammer (the M-16 or DPMS "smooth front" AR style works best), but it's much easier to just drop in a 9mm hammer, which can be left in for use with .223.

buffers and springs can you use a H2 buffer and std spring ? or ?

9mm carbines (again, talking about the Colt system) require a 9mm buffer, but that, too, can be left in for use with .223 in most cases.

finally Barrel's I thinking 10 1/4 or 11 1/2 length wanting to go with a SS barrel
who mfg's SS ar 9mm bbls in the shorter lengths ? what twist ? all I've found in SS is 16"

Not aware of anybody offering a stainless 9mm barrel. You can get short (<16") 9mm barrels from Rock River, TROS or Bravo Company.

One last thing does anyone make a side cocker upper for the ar 9mm

I seem to recall some folks have used the ASA side-charging upper in their 9mm builds; you'll just have an empty gas tube hole since the uppers are built for .223. Not a big deal.

HTH!

 

[absrio]

I use the Colt style which means I can use CPproducts SS mags if I wanted to but I use Promags right now and have had great results.

For magwels there are lots of options dedicated verse slide in the magwell. I bought the RRA and I highly recommend it, been 100% reliable.

For the Hammer since I bought a RRA complete Upper I bought thier 9mm hammer at the same time. If you do not go with that you have to get your bolt ramped then use a DPMS style hammer. I used a regular spring and ordered a dedicated 9mm heavy buffer from Spikes Tactical. It is supposed to help protect the bolt release, keep the bolt closed longer, and reduce recoil.

I have not seen to many SS barrels for 9mm. Most of the 9mm barrels will be 1/10 or 1/15 twist. If you find a 16" SS barrel you can always have it cut down.

Spikes Tactcial does have a few side cocker uppers for the 9mm. You have to call them to get info.

 

[bigcraig]

Shooter521, pretty much summed everything up in regards to 9mm AR's.

A couple of things I recommend, only because I feel that do offer improvement and/or work well.

1) Bolt ramping: The idea behind this mod is to match the same contour of a 5.56 carrier, thus reducing some wear on your FCG. This is not totally necessary, but I like it.

2) Hahn mag blocks: IMHO these are the best made and come in different configs. (And yes I have tried a others.)

3) CProducts mags: All of mine have worked very well for me, and they are now cheaper than when I first bought them, around $17, which is hard to beat for a 32rd smg mag.

4) Slasher 9Q buffer: This buffer weighs 9oz, made of stainless steel and is longer. The extra length is good as it reduces the distance the bolt travels which helps reduce the risk of breaking the bolt catch.

 

[shooter521]

4) The extra length is good as it reduces the distance the bolt travels which helps reduce the risk of breaking the bolt catch.

I would submit that this is only an issue in Colt 9mm SMGs/carbines, or in conversions that make use of the Colt 9mm bolt catch itself. Many conversions are designed to work with the existing 5.56 bolt catch, which has a different geometry and is FAR less prone to breakage.

 

[bigcraig]

I would submit that this is only an issue in Colt 9mm SMGs/carbines, or in conversions that make use of the Colt 9mm bolt catch itself. Many conversions are designed to work with the existing 5.56 bolt catch, which has a different geometry and is FAR less prone to breakage.

Damn you and your superior knowledge!