The die is supposed to size the case down from chamber dimensions a bit, so using the same size reamer defeats the purpose of the die.
A resizer die made with chambering reamer will not re-size the case, some reamers are made so that they require a neck reamer to finish off the chamber and make the leade, they can be used to make a neck sizer die. Notice I said make a die, out of steel that is then hardened. If you try and ream out a 280 FL sizer with a 280 AI chamber reamer, you will ruin the reamer, it cannot touch the hardened die. The only way to cut a die is to use a carbide bit, or diamond or some other exotic cutting material. I have enlarged the neck of numerous dies, to correct over working the necks of brass. I use a carbide bit, one for drilling glass, others have used Hi-Roc bits, they should work. Beware, there is alot of screaming steel, smoke and hot stuff flying when you do this, and you may break a bit or ruin a die. That being said I have always been able to complete the task successfully.
