Ed, if you like range brass you will jest love this new $23.99 trimmer design from Dave Holub. I personally use it and I verify it works exactly as shown in this YouTube video ....
https://youtu.be/XMYAdkeDPBU.... and you can buy it from Ebay and other similar sorts of "cheap source" places.
https://www.ebay.com/itm/223-5-56-Case-trimmer-HMR-WCT-Worlds-Cheapest-Trimme...It is an excellent trick for range brass lovers (and reloaders in general).
Other Calibers available:
(if you pick 8mm Mauser you can cover most of these other cases)
300 Blackout
.308 Win
.30.06
30-30
6.5 Creedmoor
.243 Win
22-250
8mm Mauser
7.62x39
.204 Ruger
6.8 SPC
Think a bit .....
any of the long or short case extended 30-06 family can use the same device by a simple set-up change for correct depth, and by that I mean 308, 7mm-08, 243 Winchester, 30-06, 270, 25-06 etc. etc. It can also do 8x57 and 7x57 as well if you are smart enough to start with the larger necked 8mm body instead of say a 308 body.
Going long bodied (30-06 length) isn't needed, and yes you can shorten the delrin body if you need to (if the hole is too deep and swallows up your case).
It indicates and centralizes off the neck shoulder alone -- everything else (including the neck diameter) is in clearance during trimming.
All it is is a Delrin body with the neck angle and rough clearance size/depth step drilled into it, facing a standard two flute HHS end mill held in place by a set screw. You set the neck length off a trimmed case (proper dimension) and it stays right there until the end mill gets dull (5,000 plus trimming ops) then you take it apart and sharpen the simple straight edges of the end mill with a fine grit diamond file, put it back together and re-set the length and go back to cutting.
No case pressure is needed to get it to cut, but please note the half wrist twist that is applied to each case during cutting -- you are seeking the cleanest clearest mate up angle to the neck taper form to get the smoothest squarest cut.
For equipment, a 3/8 drill is perfectly fine. Half inch drills get too pokey slow though.
If you have several different caliber case mouth diameters of this item, realize that swapping the end mill from A to B gives you a new set of VIRGIN cutting edges at the needed mouth diameters to use all over again ...... And you can buy suitable 3/8" HHS milling cutters for 2-3 bucks each on Ebay or Amazon. I bought spiral ground four-fluted cutters for that low low cost for my set of two case trimmers.
Remember, CLEAN THE BRASS REALLY REALLY GOOD and
resize the brass before trimming as shoulder/neck form consistency is what you get back in overall trim length consistency.
I set up a drill sideways using a small table clamping vise, trim all the cases to length and then pull the trimmer and replace it with a chamfer cutter and lightly deburr the inside of the case mouth. Outside mouth burr is
very minimal and gets removed by firing, cleaning / tumbling and resizing so I generally don't bother with any mouth OD deburr ops.