I'm new to reloading and would like some advice on shoulder bumping. What I'm noticing is that on the first pass through my FL sizing die the case lengthens of course, and after a couple more strokes the shoulder is back about a half of a thousandth (or not at all), and sometimes further passes will get me about 0.0015 or maybe 0.002, which is what I'm trying to obtain. Adjusting the die less than a tenth of a turn deeper gets me too far, sometimes 0.0035 or more. I can't seem to find the middle ground that gets me 1.2-2 thousandths on the first pass. First time the ram comes down (full stroke) there is a gap between the die and shell holder about the size of a sheet of paper, and second or third the die touches. With no case, the die touches. Appropriate "cam-over" at the end of the stroke. I attribute what I'm seeing to some slop in the press, not sure if I should change anything.
What would you do? Does it sound like I need to work on getting better adjustment or is this acceptable technique?
Equipment:
RCBS Summit press, bolted solidly
RCBS FL sizing dies & shellholder
Measuring shoulder with Larry Willis digital headspace gauge (confirmed my technique with them, measurements are consistent and repeatable)
Norma 6.5 Creedmoor brass, once fired, deprimed and cleaned, lubed