Some info from experimenting, searching and replies from others:
1) May 2, 2017 - Jimmy0861 posted that Ruger mags would not work in the Hunter stock. My fault, I did not remember this conversation or I would have brought it up since it conflicts with item #2 below.
2) Aug 10, 2018 - Jimmy0861 posted that Ruger AICS .223/5.56 magazines are correct for the Hunter American stock. Based upon that post, since the Ruger mags are readily available, reasonably priced, and I already have 3 of them, I decided to order the stock for my Ruger American Ranch Rifle in 300 Blackout when they become available. Oh, the Ruger AICS mags work perfect in my Ruger Precision 5.56 rifle.
3) Aug 29, 2018 my Hunter stock arrives, but all my Ruger mags are too low to feed (bolt doesn't touch the base of the cartridge), but do snap in place. Magpul tech support suggests "tolerance stacking", so I install the stock on another Ruger American with the same failure to feed in the same manner. Stock repeatedly removed and reinstalled with no improvement X3. Stock and trigger guard bolts installed to torque specs using a torque screwdriver.
4) Trying the Ruger mags without the Magpul trigger guard installed (holding them as far up into the stock as they will go), they are still too low to feed. Note: Even with the trigger guard installed, it's not like the trigger guard is holding the magazines low in the stock that you can overcome by putting hand pressure on the bottom of them in an attempt to hold them up further in the stock.
5) Trying the Ruger mags without the action in any stock (holding them against the bottom of the action...a bit awkward to do), they do feed with the bolt face making good contact with the bottom of the cartridge.
6) Magpul tech support suggested filing on a Ruger mag...that doesn't work. A flaw in filing is that no matter how much material is removed from the top of the mag, the Magpul mag catch will only hold the mag so far into the stock. Another flaw is that removing material from the feed lips to allow the cartridge to stick up further results in the the magazine not holding the cartridges in the mag (feed lips are too far apart). There's only a short distance between the feed lips holding the cartridges and the feed lip distance is too far apart to hold cartridges in the mag.
7) Magpul tech support (another person) says to buy an AI (Accuracy International made) polymer .223 magazine. I am unable to find any for sale and AI doesn't seem to list them anymore. I get a message that says AI discontinued them a few years ago due to the magazines having a tendency to split along the seam lines. Can find AI STYLE magazines made by other than AI, but hate to spend $ hoping something works. Waiting for a reply from Jimmy0861 as to what specific magazine brand and model will work. I want the stock to work for me as it looks and feels great. Magpul tech support (both people) said do not alter the stock or it can't be returned.
Edited to add: Examination of the plastic and metal parts without taking the stock assembly apart showed no casting flaws or blobs of metal or plastic that would interfere with the rifle action being properly placed into the stock assembly. All surfaces looked nicely smooth.