Whatever you heared is not applicable for the Handi. Full sizing ia what you have to do, but be carefull not to push the shoulder back too far. The case needs to be flush with the back of the chamber. 223 brass is cheap so do not worry about the brass. Polish the chamber will help with extraction.
I agree with Fred.
Personally I am not a big fan of neck sizing for the handi, with the higher intensity chamberings. (Like the 243,308, 25-06, 270, 30-05 and 35 Whelen). Its just a bit different then loading for a good bolt. I feel that the action has too much "spring". If you look at a bolt, the rim of the case is less than an inch from the locking lugs of the bolt. That is very little steel to compress, move or "spring" upon firing. Conversly the Handi has no locking lugs, it has a breech face/recoil shield that the case head sits against. But the barrel is connected some 4+ inches INFRONT of the cases rim at the hinge. This makes for a good amount of steel to deflect or "spring" upon firing. A couple factors are at play here, but it my opinion this is the reason that the neck sizing is not so good in a handi type action. (With high intensity calibers.)
(Many here know this.) What neck sizing does for you is work the brass less thru the body of the case. But also stops you from moving the shoulder with a FL resize. Combined this makes the brass more stable, IE less difference shell to shell. You tend to get better accuracy and longer brass life. But with the Handi and the "spring" in the action is different and the shoulder will move on you. After a couple loadings will no longer close on a your loaded case.
What I do is a modified neck sizing with a standard FL sizing die. Using good brass. Preferably new, but not imparitive. Load and fire an amount of cartridges. Back at your loading bench, be certain the cases are shot from the Handi. Set your die up so its about 1/16+ off the shell holder and tighten it in the press. "Smoke" one with a candle and run it all the way up into the die. This will partially resize the sides and part of the neck. Pay perticular attention tothe soot on the neck and shoulder of the case. Repeat as you adjust the die down. Stop when the complete neck has the soot removed and the shoulder is just kissed by the die. (Be careful NOT to push it back. Its better to stop a couple thousands early.) This is a suedo neck size and has worked well for me when loading for the handi single shot action.
Something else I have found is to avoid the heaviest of loads. It not for the guns strength. Its perfectly safe with any commercially avalible load for the calibers the factory has chambered in it. Its to mimamize the "springing" on the action I mentioned before. I have a couple larger, higher pressure calibers in handi's and I do enjoy them. It's my opinion that the handi would be best served with rimmed cases loaded only to about 45,0000 cup.
CW