OK, question:

I've got an M203.  I've a Knight's QD mount.  I've got an RAS.  I don't have yet but will soon have a Bushmaster 14.5" M4 upper.

How the heck does the 203 mount to the RAS?  I know the front mounts to the barrel with the QD mount.   But how does the rear of the 203 attach?

ok, I cant help you with your question, and I'm sorry. But, I gotta know, is it a real 203 or a 37mm launcher?

KAC RAS bottom handguard panel(Not the rail panel, it is the bottom the handguard section)has to be removed.  you simply clamp on the M203 just as you would with any other M16/M4 rifle.  

If you have a free folat RAS, you are SOL.  

I thought about getting a M203 with 37mm tube, but just can't see spending the 2500 for a flare gun.  well, I actually could, but just got too many project in froint of me.

Please post some picture of the 203, you lucky dog, I love that thing.

It's a real 40mm in the flesh.  Here's a photo:

[img]http://mysite.verizon.net/vze2wxvr/files/M203.JPG[/img]

Now was I supposed to pay a tax stamp on this??? ;)

Phil, you could only be asking this question because you don't have the Operator's / Armorer's Manual that comes with the M203 QD Mount.  Send me a mailing address and I will send you one.
Basically, the rear end of the M203 receiver is about 270 degrees of a circle and has a big diameter roll-pin at its 6 o'clock position.  The 270 fits around the chamber and projects back into the barrel nut's forward facing groove.  The roll pin passes into the 6 o'clock gas tube notch of the barrl nut.
The QD latch itself passes over the barrel groove in front of the front sight.  If you upper is milspec, you should have no problem.

How in the hell did you get a 40mm grenade launcher in NY?  Any NFA weapons are not allowed in NY, or at least I though?

There's a guy on http://www.lightfighter.com selling a 203 RAS mount...  the actual RAS mount.

In the trading forum.

Answers:  

Answer #1:  NFA weapons are generally not allowed in NY.  However, large bore destructive devices like an M203, a Street Sweeper, a cannon are all legal.  However, getting local law enforcement sign-off is out of the question, considering I live in New York City.

Answer #2:  The M203 is for my registered receiver M16.  Which is stored in Florida with rest of my class 3 weapons.

Alex_F, I took a look - I do see a QD mount for sale which is used to secure the front end of the M203 to the M4 barrel - is that what you were referring to?  By the way $300 on that part is way out of market, I just paid 175 for one.

My mistake!