Swing the upper open and take a look at the upper receiver just below the feed ramps. If could be that the mags are low feeding and causing problems.

Without a mag in the rifle, pull back on the charging handle, and ride it back forward very slowly.  The B/C shouldn't hang up as it goes back forward.  If the B/C does hang up, try it again, but this time hold the trigger back to see if this solves the binding.

If neither of the upper suggestions are the problem, then it could be a weak recoil spring and/or recoil spring end of coil winding bur that may be hanging up/scrapping on the inside of the receiver extension (buffer tube). If you find recoil spring end is scrapping down the inside of the tube, you can use a file to remove the bur to solve the problem.  Also don't forget to lube the buffer, spring, and tube before reinstalling the parts.

tommygun2000,

The hammer needs to ride the carrier at all times since this lowers the hammer (sears, both primary and disco) below the corresponding sears catch points to allow them to engage/function correctly.  If you lower the top of hammer pad too much, then the hammer will not be lowered enough to allow the sears to engage.

Now having said that, the top of the hammers firing pin contact pad should glide past the firing pin collar as the carrier moves back forward into the locked position.

If your having problems with the hammer/carrier binding with the hammer retained on the disconnect, then the problem may be that the hammers top edge, or bottom of the carrier is rough (surface friction), the firing pin collar is not flush with the carrier ramp (read a bump that the hammer has to climb past on the way forward, or the tail of the hammer may be too long and the hammer is just getting wedged between the carrier, and back of trigger*.

* If the disconnector spring is installed upside down (the correct install is large coil side goes into the hammer rear slot), it will bind the disco in it's correct movement and this binding will act the same as if the tail of the hammer was too long.

Quoted: I'll be ordering a new carrier or maybe a complete setup shortly to replace it.

That's kind of like throwing out the baby with the bath water.  

Why not just polish out the bottom of the carrier with 400-wet/dry sandpaper.  As for if the FP stop collar is little too large in diameter for the ramp, just chuck the FP up in a drill and spin/file the collar down to flush out to the carrier ramp.