Wait, why can't you just take out the whole decapping assembly from the sizing die, and then just run the completed rounds up into the die? Is the concern that the bullets themselves will be deformed, dislodged, swaged? Is there something else I am missing? I loaded a few hundred rounds of 7.7x58 Japanese Arisaka and when I was at the range, three of them would not let me close the bolt all the way. It was close, but even with a little more-than-usual force, I could not close the bolt so I took them out and out them aside. I have been planning to just re-resize the completed rounds (after pulling out the decapping stem). I set my dies to only bump the shoulder back about 0.002 inches and I think these rounds probably just did not get bumped back enough? I don't know. Maybe the length is just a little too long and the bullets are hitting the rifling? It is once fired brass from that rifle, so maybe they should not need to be sized anyway and hence would not benefit from re-resizing?
But you can you just do that, remove the decapping stem and resize the loaded rounds?