Last week I bought a 'TEC-9' or Intratec DC-9. I know it's a cheap ghetto-gun, but I thought it would be fun to have this little SMG looking thing for blasting.

The problem is that sometimes the rounds won't chamber and they end up with the bullet pressed down into the case. This happens often, I can't fire 4 rounds with out it doing it.

Any suggestions?

Also, this thing would be a lot of fun with a red dot on it, does anyone make a mount?

Here's the typical things to do with a mis-feed that's pushing the bullet back.

1. Get a new magazine.  Bad mags are the "usual" cause.

2. Try a different brand/type of ammo.

3. CLEAN the gun.  Really well.  Then lube it properly.  
Clean and LIGHTLY lube the magazine.
Make sure the mag spring is in the right way, and not stretched or kinked.

4. Try a new recoil spring.

5. Check the magazine latch to insure it's not holding the magazine too low.  (Do this only AFTER trying a new magazine.  Could be the magazine, not the catch).

6. Have a QUALIFIED gunsmith polish the feed ramp.  
The idea is to DE-BURR or SMOOTH the ramp, NOT make it shine like a mirror.  
Remove the absolute MINIMAL amount of metal you can possible get by with, and don't change the shape or size of the ramp.
MOST people who "polish" ramps ruin them and actually make more trouble.

I beleive they're out of business.

I'm shooting regular Winchester '100 round Value Pack' 115gr. FMJ hardball.

I've read in some places that as long as you use hardball, they're totally reliable, while others say that they never work.