fb-That's quite a lot to take in.
Originally, I had received two new magazines of which the spring was installed backwards and due to a previous post you showed some pics of what it was suppose to look like so, I disassembled and reinstalled correctly.
I don't know if the slide stop has much to do with this but the machining on the rod that goes through both sides is terrible(notice the photo) the notch in the center is smooth, however. The little tab that extends into the frame and triggers the slide to lock back seems to be a bit long to me and may also be rubbing the bullet ogive. I guess you'd say the 230 gr has a "chunky" ogive and with that, it could possible be al problem as well. If the cartridge moves forward a bit as you're shooting and say it's the last one in the magazine, it could move forward enough to rub against the tab on the slide stop. Again, not sure if that's the problem.
With the magazine being basically new as is the spring and the recoil spring has less than 500 rounds, I don't think either of these is the problem area.
All in all, I think the shooter is fine and the same ammo was shot with the Glock today and in times past at the range it's been used. While these two are not perfect each and every time, I just don't know without grasping for straws, where I'm at with this. If it were me, it seems there would have been problems with the Glock 30 and the 4506 as well. both have had the same ammo with "nary" a hitch. What's your feelings on the slide release? Tool marks causing a problem or the extended tab or it's angle?
Might I ad that the slide stop pin is the devil to get out. I have to take the end of a wooden dowel or anything hard plastic to shove it out.