Well,
That may work.. but its not correct. the fact that your seeing a bulge form, should be telling you something!
Yes you can use a FL sizer to neck size. You need to "smoke" the case. Back the die out a couple turns and set the lock ring. (NOT the set screw.) Re-size the case. Notice how the residue is removed from the neck of the case only. By quarter turns, repeat this until you are ever-so slightly from meeting the neck shoulder junction of the case. Here is where you must be careful as you do not want to move the shoulder back at all. Lower the die just a bit, remove the Case and closely inspect the shoulder, you should be able to see the light contact. This is all you want. Now hold the die AND locking ring. Remove while holding position. Once loosened, tighten the lock screw on the lock nut. Your die is set to Neck Size only.
I do this for all calibers (accept autos). If an improvement is realized. I go out and buy a set of LEE NECK SIZING DIES. Then reset the FL die to FL resizing. As a rule, all my guns shoot reloaded, neck sized cases. Be sure the cases stay with that gun/Once neck sized, they are NOT interchangeable with ANY OTHER GUN.
I have herd the argument before about only using FL sized cases fro hunting. IMHO, Its HOG WASH!! What do I go to the trouble of working up accurate loads for then??? All modern bolt actions have the ability to remove the firing pins. Just remove it and run all cases thru the gun at home to assure there will be no problems, if your worried.
I have loaded multi hundreds of thousands of rounds. I know if there will be a problem with a particular cartridge after I seat the bullet. Pay attention to what your doing and don't be distracted. You will see/feel any inconsistencies. Sure I have made mistakes, we all do, but you will find them if you watch and be aware of the problem areas.
I have a spot directly in front of me, eye level, at my bench where my scale sits. I have a couple of my problem cases. This serves as a constant reminder of what happens when you so not pay attention!!
Hope this helps and is understandable.
CW