Does anyone here own an RRA NM A4. I'm looking for a gun I can customize as well as something that is accurate. I'm also thinking of the Entry Tactical. What would the accuracy comparisons be between an Entry Tactical 16" and a NM A4 20". I've heard in the NM model with the 1/8 twist I can use a bit heavier bullet as well. Can I do the same in the Tactical?

Very different animals.  If you want an extremely accurate rifle the NM is it.  It will also weigh around 10-11 pounds, or more, if you balance it out.  My NMA2 weighed 11.  You won't do much "customizing" to one either.  The barrel under the handguards is a solid 1 inch in diameter right out to the front sight base.  The NM free float tube limits doing anything to the front end of the gun (grip area).  If you buy one to customize you will be removing the tube, tossing the barrel etc.

Figure out what you want the rifle to do then research the specs and possible add-ons before sinking the funds into a specialty rifle that isn't a very flexible platform.  If you want to empty entire magazines into a silver dollar at 100 yards from the bench, and don't want to carry it around much, buy the NM.  Otherwise there are better options.

I have NM A2 and love it.  I use it for CMP matches and have complete confidence in the rifle.  I just wish I was a better shot to take complete advantage of it.  As the other poster pointed out, you're really not going to be able to change much, but there really is no need to.  I probably would get the A4 with a removable carry handle if I were buying one today, but that's the only change I would make.  I addded lead to the stock to balance it out, and it's quite a heavy beast now.

Yeah, and a Ruger 10/22 has more recoil!

What are some of the other options you would consider. I'm leaning now away from the NM towards some platform that would let me customize. Maybe heading back toward the main purpose of the gun which is to be lightweight, have a lot of firepower, and easy to maneuver. I also started looking at LMT but they are quite a bit more expensive. On the comparison chart listed somewhere around here, they compare very well to other manufacturers but am I as the average person going to tell. RRA gets very high praise from a lot of folks.