the whole priming with folding trays idea isn't the best one Lee's had. I just am not enamored with that. The idea of having to shake it to feed and more to feed the last three is not my idea of a finished product
So far I've used the folding primer tray on 3 Lee products: 1) Bench Auto Prime, 2) Automatic Case Primer (ACP) Press, and the 3) Pro 6000 (Pro-6k)
1. The Bench Prime worked well but required a certain stroke to vibrate the tray just right to keep the primers flowing. I found it easier to just tap it as I removed cases...it would feed all the primers in the tray.
The weak point was that it required the use of Lee Priming shell holders and the collar retaining it cracked under pressure.
2. The ACP was a major step forward in that it doesn't require shell holders. It auto fed and auto ejected cases. Cases were centered over the priming ram by fingers in the upper assembly. It primed cases uniformally below flush with good feel. This was my first experience with the last 3 primers not feeding if there wasn't a column of primers pushing down.
The weak point of the ACP was that the reciprocating platform that supported the cases would sometimes flip the next primer when rising. A smooth stroke was required for flawless operation
It is still my favorite priming tool for seating Federal primers for my .38Spl match ammo.
3. The Pro-6k is a huge leap forward in handling primers from the tray to the priming station. I didn't even know there was a pin to vibrate the tray until reading about it here...primed my first 200 .45ACP just fine; maybe I'm just used to looking and tapping the tray. It does have an issue feeding the last 3 primers; I just load another full tray as the chute get about half empty.
What I really like about the Lee systems of priming are the trays. I can dump a whole flat of primers in the tray, shake them for orientation, fold it, lock it, and they are ready to go; I usually load 2-5 up before I start.
I hate filling primer tubes. I've done the hunt-n-peck, the Vibra prime hand tools, both DAA electronic primer tube fillers and the Dillon tool. The only thing that seems easier is the primer collator from Mark 7 for their 10-station presses...they got the price down from $1k to just under $700, but you have to own the press first $3500 - $10k