non-colt magwell blocks, not that it matters. colt smg upper. car stock. colt style car stock buffer. DPMS pre-ban lower.
 action cycles & loads round. fires once, won't pick up the next rd.  manually cycle action, fire again. same thing again.
 the hammer has a "step" in the face, I am guessing this is a semi-auto hammer. The bolt has been ramped, and runs fine in my full-auto lower.
 suggestions?

I am so overwhelmed with the outpouring of technical expertise from the members of this formum that I am all but speechless.
16 reads, not a single word in reply, not a single e-mail related to my difficulty.

not even a smart-aleck reply!

thanks for the help.

It is strange that nobody has said anything!
When the round is fired is it ejected correctly?
are you getting any jams/stovepipes? I had a problem like this but it just turned out to be simple drag on the bolt. Like a dumbass I had applied some grease to the bolt (dumb) and it slowed the bolt enough that my 9mm became a single shot or jam-o-matic -- I went back to good old CLP.  
If you are using a Colt style one-piece magblock, it might be up a little too high and the ejector is rubbing on the bolt. The ejector should be up in the bolt face area but not so tight that it's acting as a brake.
Sorry I can't give an better reply.

Good Luck

First, welcome to the board.

After the round is fired, is the bolt being blown back?  It sounds like what AR-fan described, as if the bolt isn’t moving backwards.  What mag block are you using?

you have im mail.......

finally suggestions. thanks!
looks like problem is the buffer sticks in the buffer spring. will try sanding the outside of the metal buffer off 1st, before I spend money on another buffer/spring assy.
before I do that, I am having a C-2 "make" it into a SBR (it's preban AR) so I can use my suppressor and a shorty upper on it.
thanks for the response, though it was slower coming than I expected.
raffica22