For all you handle pullers out there...(sorry, it's a bit wordy)...

Many of you, I am sure, if asked whether it was a waste of money to spring for the Dillon [insert other brand if necessary] press cover and/or quick-change covers, would likely respond "YES". Had I not happened into them with some equipment I picked up used, I likely would not have spent the money on them myself. Many of you use old sheets, pillow cases, trash bags, etc., primarily for dust/debris mitigation, but...

I have a 550 mounted to a bench, in a spot that I was only slightly concerned about. So slightly, in fact, that I had even forgotten my concerns, and have continually procrastinated on re-arranging the loading room (in the basement). Well, a few nights ago, we had an overflow incident in the bathroom on the main level. I did not discover it until a bit later, and the water locations/patterns on the floor led me to believe it was very minor. It did not raise major concerns at the time.
Next day, I was in the loading room to grab something, and had a "HOLY SHIT!!!!" moment. The empty, and exposed, loaded cartridge bin on the covered press was filled to the rim with water. A glance at the ceiling confirmed that water had migrated along the baseboard in the bathroom, and traveled down along the furnace duct, and into the load room (from the ceiling). Definite water stains on the ceiling around the heat register, and some water staining on the bench, as well. I guess the overflow was more involved than I thought.
On to the good news...I could see no evidence of water damage to the press cover, so I tentatively unzipped it and removed it. What do I see? Thankfully, nothing out of the ordinary. I could not find any signs that any of the water had entered the press. Nothing on the top side of the tool head, powder measure, primer system, and nothing in the shell-plate area either. Needless to say, I immediately unbolted the press, and moved it. There was some minor swelling of the bench where water had migrated under the strong-mount legs and congregated around a couple of the bolts.

I tossed the remaining primers, and the small amount of powder that was still in the hopper as a safety measure, but that's about it for loss.

Press Cover = 1; Water Leak = 0.

Was my press in a less-than-ideal location? Yes, my bad, but I am very glad that I had that cover on. Had it only been fabric, and not something water proof/resistant, I would definitely have had to break down /dis-assemble the entire press, toolhead assembly, etc., and thoroughly clean and lube.

Just my experience in this situation, but thought I would put it out there for consideration. Maybe at least an upgrade from sheet/pillow case to trash/plastic bag?