I am going to assume that you have the basic 79° crowning cutter and an appropriate pilot, yes?
If you are going straight from the hacksaw finish to the crowning kit you may have problems if your sawn cut is not square to the bore.
If you know any Machinists at least ask them to face the sawn end square before continuing.
If not, saw as good as you can then check with a set square and file it if it is a little bit off.
Also, remove any burrs, VERY CAREFULLY, that get pushed into the bore, BEFORE!! you insert the pilot of the crowning kit.
If you want to end up with an accurate rifle, DO NOT, run the crowning cutter in your favourite cordless drill! Get a tap wrench or some other means of rotating it by hand. You have much more control this way.
Use lots of cutting fluid, rapid tap, Rocol RTD or equivalent and take it slowly, removing the tool frequently and cleaning out chips. I would do 1 rotation, clean, relube, another rotation etc etc. It is important that you keep the chips clear so that they do not get around the pilot and mark up the bore.
Hope this helps.
