Correct, it spaces off the shoulder.
I got the trimmer yesterday and it appears to be very well made. I trimmed a few cases and it is extremely fast. Each case takes maybe 2-3 seconds to trim, so you spend more time picking up and setting down cases than you actually do trimming. I think once you really get into the groove you could easily do 10 or 15 cases a minute without trying too hard.
The trimmer is basically an end mill that chucks into your cordless drill, and there is a collar that slips over that and is held in place by 2 hex set screws. The collar has a bevel that matches the case shoulder, and the position of the collar on the shaft determines your trim length. It's a little bit of a pain to get the trim length where you want it - that's one of the few beefs I have with it. I used a case that was already the correct length as a gauge to set the collar.
Here's a picture to show what it looks like - I can't find my camera right now.
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The trim is perfectly even and smooth. There are no burrs on the inside or outside of the neck, so if you were shooting boat tail bullets I don't think you would even need to chamfer. The cases will still need to be chamfered for flat bottomed bullets, though.
Trim lengths appear to be pretty consistent, usually within 1 or 2 thousandths of each other. I did run into one case that ended up about 7 thousandths longer than all the others. Since this trimmer spaces off the shoulder I'm guessing this was a case that didn't get sized down as far as the others, for some reason.
I do think that the hand holding the case will get pretty tired from gripping the cases after a while. I'm guessing a thin pair of grippy work gloves would help a lot.
Overall I'm pretty pleased. It's not a Giraud by any means, but it is ridiculously fast and a heck of a lot cheaper. Is it better than a Possum Hollow? I'm not sure, but its head and shoulders above the Lee trimmers.