I have got the hot tip for you on case trimming. Been meaning to relate this for some time. This method is very accurate and fast.
some background first;
On a lathe when you use a 5C type collet your finished part length is at the mercy of the stock's diameter consistancy. On a 5C type collet with a normal pull type of closing mechinism this relationship works out to .003 variation in length for every .001 of diameter change.
So if you use a collet in your lathe to trim cases to length you can get close if every casehead is the same dia.
Problem is they're not! and that results in you having to find the largest and smallest case heads and then finding one that is in the middle and then setting up the lathe around the case in the middle and living with the variations. This is also what is wrong with many case trimming lathes, like my older RCBS. It uses a collet that is pulled into a taper to close it and the length varies based on case head diameter. Some newer ones use the rim thickness as the reference which is also not consistant. Also trimming 100 rifle cases on a crank type trim lathe gets old pretty fast.
Then I remembered I had this device. Have you seen one of these Collet Closers, they are fairly common? Everybody sells them and they are about $50 for a new one and way less for used ones.
This device operates as a "Dead Length Collet Closer". The collet is threaded into an adjustment ring which is captured in the base of the tool. When you operate the lever an excentric pushes a tapered collar up around the collet to close it. The collet never moves in or out, only the closer ring moves, so case head dia is irrelavant to final trimmed length.
I simply use a Lee Cutter with an 8-32 SHCS with the head turned to about .302 for a pilot, and then you hand feed down to the quill stop with the mill or drill press turning.
It is fast and accurate.
The collet is any used up 5C collet or an Emergency Collet with a .470 counter bore about .06 deep turned into the face.
Note: Most all collets are made from 12L14, and then case hardened about .01 deep. It is easy to break thru the case hardening as it is not even that hard, maybe low 50's Rc. Note the collet I used has been faced, and was a normal 1/8" collet before I changed it.
Emergency Collets are made the same way but not heat treated, so they can be easily turnned to what ever diameter or configuration you need to hold a part. I have many that have odd shapes milled into the face for turning of a spud or boring of a hole in a lathe setup which many times is much faster than doing it on a mill. Especially like in a ctr drill, drill, tap scenerio where the tool changes on a mill would eat you up. On a turret lathe it's just a matter of indexing the turret for the next tool a few times, and then you're back at the start for the next part.
Note: There are a zillion cartridges that use the .30-06 case head size so one collet can do alot of different cases. Obviously there are other common case head sizes so you only need a few collets to devote to this project. I have 2 so far.
Hope some of you machinist types can use this info, but the beauty of this is, you don't really need to be that much of a machinist. You could have a shop or buddy make the collets for you and just use a drill press and this type of fixture. The key is the "Dead Length Collet Closer".