Actually the Norc barrel nuts are a little off as well. The Norc ones are longer than standard. Not a lot but enough that handguards don't fit properly.
This is the reason you cannot readily swap out standard hand guards onto a DA556 without removing material from the guards where the barrel nut teeth fit into them.
You will notice the barrel nut is always slightly past the notch in the guards where they are supposed to go. Ditto with the CQA clones. You could just dremel out the guards in the recess to make the notch wider all around though.
I just went through this entire process on my barrel swap with my M16A1 clone.
The Norc DA556 has round caps. You will need to swap this for a triangular 0.625" diam hole one.
You will need to remove the gas block.
The Norc pins can be a bear. I have attempted to remove 3 gas blocks in my time. 2 of them I was successful relatively easy and 1 would not come out; the Norc DA556 lol
Here's the kicker, if you cut off the gas block to change the cap and barrel nut, you have to find a new gas block, the taper pin holes will very likely not line up.
Now you're looking at smith work to redrill the pin holes. Tier 1 did mine (outstanding work) but it was $200 for work and shipping plus an almost 5 month wait. They could not hammer out the pins either they had to physically cut the FSB off.
So remove block (if you can) swap the round cap and barrel nut for NA standard type (unless you want to dremel out the A1 handguards you may not have to change the barrel nut. I just swapped mine as I had the block off at that point anyway.
FYI the norc DA556 barrels are excellent quality, mine shoots 55gr FMJ bulk like a fackin' lazer. Very well made.
A1 is the way to go brother, best AR15 config of all time
