Guess I do now.

New 16" middy, recon barrel with matched bolt and new carrier.

Got the first 20rd mag off no prob, slow fire.  
Put in the next mag, one shot, no feed, again and again. If I was lucky would get two off then nothing.  Would run the carrier back far enough to eject, but not pick up a new round.  Tried different mags, no luck.  Was shooting Q3131, so didn't think it would be a power issue.  Did have a new carbine buffer spring in it, changed that to the old one thinking that might be it, nope.  This upper has a PRI flip up front sight, so I suspected the port was not properly lined up, messed with it a big and no luck.  Finally pulled the bold and carrier out of my M4 and tried it and after 15rds continous I swapped the matched bolt to that carrier and it ran just fine for the next 240rds.  

Then the real test?  Tried the "new" carrier in my M4 and it ran just fine.  

What gives?
Any ideas?

Thanks for the advice Dano, I did run the new carrier in my M4 and it ran fine, I totally understand what you are getting at here, so I'll pull it off and start to slowly polish it up, hopefully that helps!

when you swapped carriers did you also swap bolts?

Quoted: when you swapped carriers did you also swap bolts?

Yes, so I put the matched bolt into the swapped carrier to keep the original bolt with that upper.

That's almost confusing for me to read

yeah it is , did you keep the botls with their barrels or did you swap out the entire bolt carrier assembly when you switched?

Tweak, yes, I kept the bolts with thier barrels.