@ar91599
You do not need a gauge. Watch the video Feenix posted. You need your normal die and a caliper is really all. The rifle will tell you when the case is sized properly and the caliper will tell you if you need to trim based on SAAMI specs.
Steve
Lot's of good suggestions here and above.
Your rifle will tell you when you have the right length from base to shoulder, your bolt should fall freely or at least with little to no resistance.
For overall length the simplest solution is the Lee case gauge trimmers.
Use the Lee Cutter and Lock Stud with the Case Length Gauge & Shell Holder to trim cases. Can be used by hand or with an electric drill. Works on all brass less than .475 base diameter. If you are looking for trimming cases with a base diameter larger than .
leeprecision.com
They have different bases and mandrels that are round/caliber specific.
Lee Precision Case Trimming Tools
leeprecision.com
I used the original in conjunction with a cordless drill for many years and it worked great. They do have a specific part now to make it even easier.
If you have a SAAMI spec chamber Hornady Case Gauges work great and they will even make you one to spec if you send them a few loaded dummy rounds.
Personally I've found it difficult to actually measure shoulder bump manually with a caliper but if you slowly set the resizing die down until you have a good fit in the chamber again, the rifle will tell you all you need to know.
If you're loading for multiple rifles shooting the same round you either need separate dies set up to get the optimal fit in each or you compromise on a length that works in all of them. Otherwise you end up having to readjust the dies for each separate rifle and that's a great way to induce errors.
Broz and I use similar T-7 presses and you can just change the tool head and have separate tool heads set up with dies for each rifle. That is not an inexpensive solution but it is probably the best if you're not simply going to set up separate presses for each.
Here's another video using the Whidden, Hornady, and Wilson case gauges.
The Whidden Gunworks shoulder bump gauge enables you to adjust your sizing die to the desired measurement. The bump gauge is attached to your calipers with a set screw and determines the measurement from the base to the shoulder of the case. We now offer a Thumbscrew Pack that will fit the...
www.whiddengunworks.com