I think I have both ends of the spectrum covered, as far as bench priming tools go (at least the ones that are designed to be tube/tray fed), with the both the Forster Co-Ax Primer Seater and the Lee Auto Bench Prime
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The Co-Ax is very precise, smooth feeding, and gives great feel to seating the primer. It is of all metal construction
It doesn't require the use of shell holders for different cases as the jaws are adjustable. The primers feed from a tube with the primers facing forward to minimize potential injury should a primer ignite.
Primers slide into the tube from the built-in tray, the tubes have a 50 primer capacity
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The Lee Auto Bench Prime is mostly metal, but the priming assemblies...and of course the tray...are made of plastic.
It requires individual Lee Priming Tool Shell Holders to work with different case sizes. Primers feed from Lee's folding primer trays which will orient and hold 100 primers.
It is very important to completely release the priming handle between each stroke to aid in reliable feeding of primers from the tray to the priming assembly...don't remove the O-ring as advocated on YouTube
Observations:
1. The Lee looks more awkward than the Co-Ax but is actually capable of higher rates of priming as you can use both hands to place and remove cases
2. The Co-Ax allows for more adjustment to your specific case size, but it takes more effort (3 screws to adjust)
3. The Lee tray is more convenient...you don't really have to touch the primers at all...but the hinge is folded plastic and an obvious wear point. Also it will sometimes require a bit of jiggling to help feed primers
4. The Co-Ax is more rugged, but also cost twice as much