I've found that...as good as Metalform mags are..that some of their flat followers need a little tweak to work like John Moses intended.
Ya gotta be careful, though...or you'll snap the shelf off and warp the top of the follower.
Hold the follower in front of your face, so that you're lookin' at the front end of it...slidestop shelf to your right. Grasp the top with a pair of wide pliers...as close to the front as the shelf will allow, and use the widest
pliers that the shape of the follower will allow without causing the rear leg to bend outward and mess up the angle.
Wedge a slot-tip screwdriver blade between the split in the follower and
apply a little quick leverage toward the shelf. It'll be trial and error until you
develop a "feel" for it, so be patient.
What you want to see is a very narrow "V" split between the shelf and the
front of the cartridge ledge. This tweak not only establishes that "V", but it tends to put a slight upward slant on the shelf toward the outside, and
make the engagement with the stop lug more positive. Look at the top
of the follower to see the "V". When you can see a little sliver of light
between'em...it's just about right.
Install it in the magazine and try it. There's a chance that you may have to
take a couple of shots at it before it works...so take your time and don't
put a lot of leverage on the shelf. They break off like right now when ya
don't use a delicate touch.