One last thing, at least for the time-being, that I was thinking about.
You don't always have-to, nor will you want-to, necessarily trim a case (especially in batches) before you begin working-up a load.
Here's why.
Decide on the projectile you are going to use (and this especially holds true with 5.56 for instance but sometimes with some of the 30s) and then check your COAL against your load data ... is the projectile you are planning on using cannelured? If so do a dry run and see what depth you'll need that brass to reach in order to lip your crimp solidly in the cannelure. If the neck is too long then you'll need to trim and rim ... if too short then you've got a problem, if just right then you're Goldilocks.
Now the cannelure issue does not come into play too often in 30 cal (unless you occasionally run into it when working up some M21 milspec loads or something) ... but the practice of doing a dry run on seating depth is a good one when precision reloading BEFORE you trim a bowl full of brass.
I'm probably going to draw some wicked chaff for what I am about to type here friend ... but I wouldn't spend the money on a Thompson unless you're talking about one of their new bolties (you're talking about the Center Encore). I get Thompsons for some of the wildcat stuff and I was shooting them back in the 70s (glorified accuratized pistols with awesome grips)... but what you want, for .308, is a good bolty for what you apparently want to accomplish.
Consider this ... unless you and I are talking about two different beasts.
Look in most reloading manuals and you'll notice something in quite a few. You'll see data for "Rifles" and "Pistols" and even "Cowboy" ... and then you'll see "Thompsons." There's a reason for that. Short barrels, recoil considerations, burn rates, pressure curves ... why limit yourself to those margins?
And I even get the single shot Pro Hunter series, I do. One shot one kill etc., I get it but ...
Get yourself a good bolt gun for .308 and you'll never regret it. Preferably magazine fed. The cartridge was designed for bolt guns and milspec semi autos ... not single shot pistols with longer barrels.
Anyways, pardon me overstepping my boundaries and if I offended in any way ... but you've got all that beautiful .308 and x51 brass, make the most of it. It's made for hunting and paper punching and defending your property and it is the absolute finest all-around cartridge ever necked down from 30-06 brass ... make the most of it friend.
If you really wanna do Thompson Encore in a bad way look at 7mm Mag or 300 Win Mag or even 300 SWM. Now you're talking a reason to buy a Thompson Pro Hunter.
You can get a Savage 110 or any number of solid well built bolties (Mossberg now makes a really good one) for less money than you'll pay for the Thompson.
Anyways, sorry for the LWR. Just caught myself ... reads as if I am advising my Son. Mea culpa
/advice rant off