I am thinking of looking for a 9mm carbine, my only requirments are reliability, the ability to use iunmodified sten mags, and low price.

Any suggestions?

Sounds to me like a SOCOM mag block and an Oly 9mm upper.

Same thing I'm gonna do...

Quoted: Sounds to me like a SOCOM mag block and an Oly 9mm upper. Same thing I'm gonna do...

Yup, that's your only option....

Check out Hi-Point Model 995 carbine. It doesn't look like much but it really is an impressive little shooter. Plus it uses pistol mags.  They sell for about $159.00. We have sold quite a few and have had none come back! Well, we did have one come back. The owner took it apart and put it back together wrong.

Quoted: Check out Hi-Point Model 995 carbine. It doesn't look like much but it really is an impressive little shooter. Plus it uses pistol mags.  They sell for about $159.00. We have sold quite a few and have had none come back! Well, we did have one come back. The owner took it apart and put it back together wrong.

I was wondering if anyone else would mention the Hi-Point.  They're cheap, but they're good.  Kind of like the Kel-Tec P-32.  OK, well maybe not quite THAT good.

Mine has functioned flawlessly, and grouped el-cheapo ammo in less than 5" at 100 yards with iron sights.  Enough to make head shots...

For the price, they cannot be beat.  I'm not sure if I would trust my life to it, but it's a lot of fun.

Oh yeah. I forgot to mention that Hi-Point 995 carbine also comes with a scope mount.
Garand_shooter: I am also a fan of the M-1 Garand. Own 6 of them. 5 WW2 Springfields and 1 H&R.

also a Marlin camp 9 uses S&W model 59 mags, I have one it was $ 300 and shoots nice and is  reliable

Master Piece Arms makes both a M11 pistol and carbine that accept unmodified sten mags. I own the M11 pistol (MPA30) and have had no problems with it and the $2 magazines I bought from Tapco. The pistol cost me $350 and came with a magazine and fake silencer.

The carbine version is called the MPA20. As of now MPA doesn't have a website, but you can contact them at 770-832-9430

It's roughly 15 years old, and not box magazine fed, but my Ruger .44 (Now Deerfield) Carbine is among my favorites.
Not sure what you want the rifle for, but this one is relatively light, quite accurate, low recoiling, and fun to shoot.  Suggested.

I guess I would be expecting too much to think that people who frequent a website called "AR15.COM" would not recommend the Hi-Point. Or any Hi-Point for that matter.

I had one. Took it apart. Crap. Put it back together. Shot it a bit. It worked (20 rounds). Still crap. Stuck it in the closet a while. Then I traded it off on a M1 Carbine, and all was well.

Trade in value? $65.

The stock is made of cheap plastic; apparently melted-down Big Gulp cups dyed black. It is hollow and has those ribs they put in cheap hollow plastic things to (not) stiffen them.

The magazine well itself has ribs inside it to (not) stiffen the pistol grip, which are PERPENDICULAR and EXPOSED to magazine travel. This means your mag can, and will, catch on at least one rib during insertion. Carving them off doesn't really help since those ribs are actually what guides the mag in the proper direction and angle. I suppose filling the hollow spaces in with epoxy would work, as well as actually stiffening it, something the stiffening ribs don't do anyway.

The stock itself flexes. Just grab it and twist. Not too hard, you might break it!

It flexes every time you fire, too. It feels like you're trying to shoot a three-foot-long black rubber dildo.

The blowback bolt looks and feels like it's made out of melted-down Hot Wheels pot-metal die-cast toy cars.

The way they retain the action in the stock is so laughable, it's not.

The sights suck.

Their "finish" is Krylon. And they can't spray evenly, either, mine had runs in the paint, including a full 4" long run on the side of the barrel.

The trigger is the same cheap plastic as the stock, and is connected by a bent piece of wire.

I could go on and on and on, but you get the idea.

Did it work? Yes. (for the 20 rounds I fired before trading it, so that means absolutely nothing at all)
Did it inspire confidence? No.
Did it inspire pride of ownership? No.
Did it inspire pride of craftsmanship and/or quality? No.
Did it inspire the feeling of a good buy? No.
Did it inspire the feeling of reliability? No.
Did it make me embarrassed to be seen in public with it? Yes.

But, I suppose that's what I get for buying crap, so I really shouldn't complain.

Other than that I can't give any suggestions on 9mm carbines since I haven't owned any others.

Quoted: It feels like you're trying to shoot a three-foot-long black rubber dildo.

Oh my...  

Yeah, it's crap but it works.