What you have described sounds to me like NECK TURNING, not trimming. It can be done on the inside of the case neck, or the outside. Outside turning will produce a neck that is equal in thickness all around, but inside turning just increases the size of the hole. Theprocess of outside turningis supposed to improve accuracy.

Again, it is all relative. Neck turning without consistency, case fit to chamber, etc is worthless. To me, I am looking at neckturning only because I am at a point where the gun is shooting 1/2" groups and I want to go better. At that point, I have to ask myself:
1) Is there enough thickness runout to warrant this? So far, I think not.
2) Is the barrel/ action/ chamber ready for this? Probably not. I shoot a stock Savage 12 BVSS.
3) Do I have a ball micrometer to accurately measure neck thickness runout? Not yet, but I do have an RCBS casemaster which can be rigged to measure this.
4) Do I have dies for this? Well, I have Forster dies which still have an expander ball. If I had Wilson or Redding dies, I might be in a better position.
5) Since my rifle is a field rifle, should I really be spending my time position shooting now that I have a .5 - .75 MOA long range hunting load. YES

So, I am stuck on question 5, but I do have a nice nect turning setup!

If your rifle is the basic sporter hunting rifle then I would say that you have a very good un-modified rifle. To get any better than what you have achieved would cost you hundreds, if not thousands of dollars and with a stock grade barrel the gains probably wouldn't be worth the money spent. If you are talking about a 100 yard 1/2 inch group then you definately have a good load to rifle match and should be very happy with that.

Yes, 1/2" @ 100 yards. I am hesitant to say this because this is a best 5 shot 100 yard group. An average of 10 groups might be more like .75 MOA, but that also is plenty good enough for me. It is not stock or average hunting rifle. The rifle is a Savage 12 BVSS in 300 WSM. It has been beeded in the stock by me and the scope base has been bedded to the action. Other than that, it is just a pretty good load and a fine Burris XTR scope. Weight(IMO, the biggest impact to accuracy) is about 14 lbs. Carries ok. Last rifle was 12 lbs, so I expect some weight.

Thndchicken hit the nail on the head. Consistancy is by far the most critical procedure in accurate reloading. Neck turning is worthless and a waste of time on a factory chamber. Some can argue it's a waste of time on a custom chamber too and I have 2 of them with tight necks. The next best thing is confidnece. Be confident in yourself. Be confident you have done everything tothe best of your ablitly, be confident in your shot. If you think that weighing cases, bullets and primers helps, then you should do it because it adds confidence. If you think turning necks on a factory chamber adds to accuracy then do it, once again for the confidence.

Even from a bench, few can hold under 1/2" @ 100 yards! That is outstanding accuracy!! Wish I could shoot that well.....