I had trouble at first with my 22 hornet encore , My chamber is oversize and has to much headspace but not to a level that is of extreme concern . Mine has a synthetic stock and I glued a rubber waher to the forend so each of the forend screws would pass through one, this free floated the for end .
I had trouble finding a bullet that would shoot very well until I tried the hornady v-max in 40 grain , loaded to within .020 of the lands(the bullet is on held in the case by about .040 of bearing surgace) it shoots groups that average .625 and my best group so far is .280 , if I push the bullet in another .100 the groups will stay under 1 inch and with each I was useing 1680 and could duplicate it with 4227 , the 50 grain v-max and the cheap 50 grain TNTs will shoot under and inch also.
Float the forend , dont use a bipod , Shooting off sand bags it makes a difference were your front rest is , Most often closer to the action is best but not a concrete rule .
Also as true on any rifle with a break action the amount of downward pressure you put on the stock will affect the gun , in other words a very light and consitant downward pressure would be best , a right had shooter has a tendency to apply downward pressure with the right hand thumb .
All the above is pretty much true for your NEF also , I have a .223 nef that I have not been able to get to shoot as well as I would like , It will shoot 1 1/4 inch groups but rarely better , I would like to have 1 inch cut off to be sure the muzzle is square to the bore and then have it recrowned of course . This is has fixed more than 1 NEF that I know of .
try these and see if it helps