M77 MkII .223 feed problem...

(Please bear with me guys - I'm going to try to be as specific as possible - the problem is not as complex as the description is long)

I bought this rifle 'used like NIB' years ago. I love it, but it's always had an issue I've sort of learned to live with. It's either worse now, or it's bugging me more. Here's the story: I load 4 rounds into the magazine, looking down from the top, the orientation in well is left (top), right, left, right. Close bolt on 1st rd,; fine, eject, close on 2nd; fine, open bolt smartly, 3rd rd. pops up and out, lying there on the other rds., or if very gently half out of mag. (see pic) Either way, I have to stuff rd. back in, and the bolt loads it fine. Every time. The 4th rd. will chamber OK. I contacted Ruger some years back and they sent me a new mag spring, which never really helped. Thinking that since the 1st rd. (left side) always chambers fine, and the 3rd (left) never does, I'd try stiffening the spring, which I did with some rubber wedges in the spring folds; No better. The mag has no 'lips', of course, but rather milled rails in the receiver that seem to serve that function. In the other pic, the left rail does have a very slightly relieved area back to the point that the follower's relief cutout is. It's a little rough there, but I've never dared trying to smooth it, for fear of taking off metal making the situation worse. It seems the problem has to be that the rail itself (non-relieved) portion is simply too narrow.
I've always hesitated to contact Ruger, as replacing the entire receiver seems a pretty big deal. However, I just read another glowing report of Ruger CS here.

Do you think I've diagnosed the problem? See any possible fix before I call Ruger? Think they'll give the time of day?

"The mag follower should pin the upper round against the left bolt rail. I suspect that you simply have the wrong follower..."
The follower IS pinned against the left rail. It doesn't pop out, just the 3rd rd when cycling after the 2nd rd is ejected. EXCEPT.... I can, and have managed to have it pop out when handled a bit roughly, like getting frustrated, and jamming said round back into the box...
The more I think about it, that's it! - Under normal circumstances, I'm thinking the mag spring has enough tension, and the rail JUST big enough, to secure the round when loading, nice and smooth. It's the 'jump' the round has to make when retracting the bolt that puts it over the edge - literally - and that only happens on the left side when the 3rd rd. comes up.
Hmmm.. Thanks guys. I think I have a good enough handle on the problem to call Ruger, which I will a bit later.
Will let you know what they say.

Well the good news is, I got right through to CS. The better news is, it sounds like they'll make it right. Just got to ship the thing now - the thing is heavy with the laminated stock too.