Lock the bolt back, seat the front of the mag into the rifle, and smack the magazine into place.  I think there are some burrs that cause it to feel like it won't fit, and forcing them seems to clean them up.

I've had 5 of the OE 20rd mags for over 2 years now as well as my 5 of the Ruger 20rd I got with the rifle new and I've never had any seating problems with the OE mags.  The fact is that they fit better, tighter and more secure in the rifle than do the Ruger mags due to their superior construction with a welded tab mag catch vs Ruger's bent tab mag catch.  Because they are a more precise fit, one has to insert them with a bit more care (ensuring that they fully engage the hook at the rear of the op rod spring guide then rocking them rearward smartly to engage the mag catch) . . . . just like we learned how to do it with our M14s in the Army.

I've had discussions with Ruger's mgmt on the design and quality differences between their current mag supplier (Ruger subcontracts their mags out to 3rd party vendors) and OE's and they have remained committed to their current supplier even though OE's are better made and can sell for 1/2 the price.  Interesting.

To be fair, I've had a couple more jams with my numerous OE mags due to differences in feed lips (that I still need to correct and just haven't gotten around to yet) than I ever have with my Ruger mags.

I am also a little hesitant to bend the feed lips until I have a better chance to sit down and look at the aggregate number of mags/start numbering them/etc.

Since I've gotten my 5ea OE mags I use them most of the time rather than my Ruger ones and they have preformed very reliably.  Early last November, I took out all of my mags, both Ruger and OE, to the range with my Mini M14 and did a 'cold weather' test of them just for grins as my initial test had been in warm weather.

Of the 10 mags, 5 of each type, I had 2 failures to feed completely, 1 in an OE mag and 1 in one of my Ruger mags.  However, I removed both mags immediately after their failure to feed and in both cases the rounds were seated with the bullet tips dragging on the front of the mag body which is a failure on my part, not the mag's. I'd failed to tap the mag to ensure that the rounds were sitting at the rear of the mag body as I was trained to do and as I trained others to do in the Army.

After tapping the mags as I should have done, both mags performed reliably.  In the service, we taught the troopers using both the M14 and M16A1, to always tap the rear of the mag body after loading to ensure that the rounds were seated with the bases against the rear of the mag to ensure that the bullet tips were not dragging as this could lead to failures to feed.  I attribute the 2 failures I had to my failure to follow my own teaching, not an issue with the mags themselves.

Funny you mention that.  I noticed a couple of times that with the green follower the OE mags come with, that the second round tends to want to nose forward of the BHO catch, which can make it drag (and might contribute to failure to feed issues).  Sometimes it wouldn't happen until I had loaded 7 or 8 rounds, but I started to keep a close eye on it.  It happened across several of my mags.

Are you switching followers?

I just ordered 2 10-round magazines. $33 shipped is reasonable. I believe you guys, but I want to try them out myself. Hopefully these are as good as the Ruger mags. I have a couple of rifles to test them in.

When will the 20 and 30 round mags be available?!

Dont know, just watch the link...

Infrequently.  Usually a couple times a year.  You just have to keep a lookout.

As for follower replacements, I think Brownells was the only source for the new style anti tilt follower for $6 and Numrich had what looked like the old style for $10. Midway does list them for $5 but have been on back order for quite a while. Til I experience a malfunction I’m not worrying about it. And I’m running 125gr. 300 blackout.

Sigh. Still waiting.