The way I have done it on my 30/30 94's is keep the brass separate for each gun and then take a fired case (normally 30 grns of 3031 with a 150 Sierra JHP but check the data as I am doing this from memory) and then sit with the gun and the press in the loading room.
First trim, chamfer and clean your fired cases. I trim every time on rifle. (Funny as I never trim a pistol round but that is another issue).
Take the fired case first try to feed it in the chamber. Feel the resistance (stop as soon as you start building resistance as otherwise you will be sizing the case in the chamber and putting a lot of stress on the mechanism) and then go to the press and with the die screwed way out (3/8" give or take) size it. Wipe the lube off and try chambering it. Feel the resistance build in the lever. You can normally get the lever to close more easily but then the resistance builds before the lever closes.
Screw the die in a quarter or half a turn and repeat.
Keep this up until the case will enter the chamber and the resistance starts to build just as the lever snaps closed or slightly before for maximum case life. Go a bit deeper (half turn) for hunting loads where you don't want the resistance caused by a bit of gunk on the case when you are looking for that fast follow up shot.
Keeping the cases separate for each 30/30 is a big deal. I am not sure why, but the chamber lengths between the different guns is really noticeable. Basically the headspace is variable between each of them. To me it is not worth fixing as keeping the brass separate is not a big deal.
This is what my shooter (early 1964 vintage) 94 will do at 100 yrds. 50 shots off the bench. The ammo was made following the procedures outlined above.
