I am thinking of buying a DPMS "custom"
made 24 extreme does anyone know about these
rifles?

What do you mean by "custom"?  I recently bought a DPMS Deluxe 24.  It has the fluted bull barrel ~1" in diameter.

I've only put 100-150 rounds through it so far but i has worked great.  DPMS also took time before I bought to answer several of my emails and a few calls too.

Custom in this case means that it will be a
"southpaw" as to I and my son are left handed
when I was talking the the rep he said it
could be done for a few $ more.
My main concern is feeding it! I bought a
Bushmaster DCM last year super accuracy
but it jammed 20%. the mags it came with
sucked they sent me two more one was the same
I bought two of DPMS's ,the bushy didn't like
those either. A Vietnam era 20 worked the best
but in Jersey that's a 20K fine and confiscation
of all arms.  

The Bushmaster 10rd mags are crap.  IIRC, it is still legal to use USGI mags that are temporarily blocked to 15rds or less.  You could also buy Colt 20rd mags that are blocked to 5rds.  Sarco in Stirling, NJ did sell USGI 30rd mags that were blocked to the legal 15rds.

Hmm,  I'm left handed but didn't even think about getting a lefty rifle!  I guess I'm just too used to shooting em the 'wrong' way.

I've only shot a little out of the DPMS mag maybe 20-30 rounds and it worked fine.  I got a steel made in england 30 rounder the day I went shooting and then got some Colt 20 rounders and it has not mis-fed yet (200 some rounds so far).

I just need a ton of ammo now!