It seems you are no longer an active loader but you want to question what a serious loader is. If you just reload ordinary ammo, especially pistol ammo you may never notice your press springing. I tested my Bair C press against a1st generation Rock Chucker with the same machine gun fired 30-06 brass using the same sizing die. The C press sprang open .007. The RC only .002. If you are happy with that sort of performance you are not a serious reloader. I respond to a lot of reloaders questions on this and other sites. One of the most common problems is guys discover at the range that some rounds will chamber and some will not. This is often caused by using a light duty press and rushing through the sizing process without verifying alk cases will chamber. I bet I have answered that question 100 times.
Yes I could form .30-06 to .25-06 and to .243 but the shoulder would vary in location with the C press. So would yours unless you checked it and sized the brass several passes. I know because I have seen the shoulder location variations. I once reformed 100 new .303 Brit cases with a Rockchucker and I easily got .002 variation just due to variations in lube and sizing speed and number of passes. I know exactly what happened and why because I measured the head to shoulder datum length of each and every one with my caliper. There would have been far worse variation using a C press. Using the Rockchucker I was able to size each case 2 passes and get them all exactly the same to within the resolution of my calipers and as checked in the rifle. I used the stripped bolt and chambered each of the 100 cases. Each case had a light one finger drag when rotating the bolt closed. I find that cases formed with that uniformity are likely to last longer and are more accurate.
D