My thought on the LEE Auto Prime and Bench Prime
I started out using the newer Lee Auto Prime just because it came in my press kit, The tray and primer ram system aren't perfect, it will hang once in a while, or the primers will stop feeding from the reservoir into the chute and it takes a few taps to get them going again, but its not too bad,
The little "Open, Lock, On" latch on the tray that's designed to allow you to "Open" the tray to load it with primers, "Lock" it closed but not allow primers to flow out, and finally click it to ""On" to allow primer flow is actually the biggest issue...
After loading the tray with primers, then switching to "Lock" I'd then put it on the primer, and sometimes accidentally flip it back to "Open instead of "On" and would dump the tray all over. (My fault, but its easy to do)
And the "Lock" position doesn't work all that well to stop the primers from flowing out, Occasionally after you switch it to "lock" then tip it up to insert into the primer handle body, primers flow out of the chute anyway.
Easy work around for this is just insert the tray into the primer handle body before you load it with primers. OR load the tray, switch it to "Lock" and put your finger over the end of the opening until you have it in position to insert to the Primer handle body.
A lot of people have posted the Auto Prime and or Ergo and Bench prime are junk and they broke the primer ram inserts right away because they were plastic, etc... (they all use the same type of plastic housed primer ram and the same tray) but I've never broken anything on the Auto prime or Bench prime and have used them for a few thousand rounds...IMHO you'd have to be cranking on it pretty hard in order to break the ram housing, or get a primer jacked up in the ram chute and keep forcing it...
Like others said, a little quality grease on the metal linkage pivot points helps a lot to smooth it out,
One gripe about the Auto prime is that slot in the finger side of the handle is uncomfortable after a short while, but enough people must have complained, because now they offer a "comfort grip" you can buy for $7.50 and snap it on. ( I haven't tried it yet, but will probably order one)
They also now have the "Ergo Prime" which looks to be similar an Auto Prime with a smoother body and the lever relocated to the front instead of the back so it has no uncomfortable slot, based on the looks of it, the Ergo Prime would be a lot more comfortable to operate, but its a few buck more than the Auto Prime and even the Bench Prime (which I don't really understand?) but I haven't actually used an Ergo Prime so I cant say 100% for sure...
I also have arthritis pretty bad in my hands so I decided to give the new Lee Bench prime a try, it still uses the same type of plastic ram housing and the same tray as the Auto Prime and Ergo Prime, but the priming is much easier.
Its basically an Ergo Prime redesigned to mount on a bench with a better leverage handle,
The first time I used it, I had feeding problems and also ruined quite a few primers, but after a little research, I found that Lee was recommending to remove the Rubber O-ring on the body which was supposed to act as a little bump stop cushion for the lever when it returned to the "Up" position, supposedly it was limiting the lever return travel a bit too much and wouldn't allow enough clearance for the next primer to drop into position. After removing the O-ring it fed much more reliably.
I also mounted it a little better and slowed down a little till I got the feel for it, I actually really like it now.
I have it mounted to a board I clamp to the bench when I need to use it and I clamp it at a slight angle (not directly at my face obviously) so after removing the primed case, I can see the next primer that dropped into position, every once in a while a primer will drop wonky and I can see it and easily correct it before I smash it into the pocket, If you operate the lever smooth and make sure your returning the lever fully back "Up" the less often wonky drops happens, "Slow is Smooth, Smooth is Fast" ...
The bench prime is definitely MUCH easier on the hands, you can prime with just 1 or 2 fingers on the lever, just be careful not to press to hard, it has a lot of leverage and a whole different feel than the auto prime. But you still get a good feel,
It probably sounds like a lot of negative issues from this post, but its really not, especially for the cost... just wanted to give you an honest thorough review...
A little learning curve, and patience and both the auto prime and bench prime work just fine for me... the RCBS hand primer is almost twice as much $, and their Tube feed bench mount is over $100, I'm not knocking them, I'm sure they're fine, I just didn't want to drop that kind of money into a priming tool.
The auto prime was basically free with my press kit, and the bench prime was around $28 online
Hope this helps ya