Many aftermarket mags for the Minis don't do well but these OE brand are made significantly better than even Ruger's as you can see below. I'm usually not a fan of 'aftermarket' mags but these actually fit significantly better in my Series 583 Mini's mag well with a much more solid lockup. They are more precise and have very little play as do the Ruger mags.
I've done feeding testing pitting the 5 OE straight 20rd mags I own with 5 Ruger brand curved 20rd mags I own and the OE actually were slightly more reliable. I fired 2 mag loads from each mag, both slow fire and rapid fire, and only had a single failure to feed. It was from a Ruger mag.
As a result, I sent Ruger's CEO a message with the results of my testing and evaluation, commenting on the higher manufacturing, and assembly quality of the OE mags vs Ruger's current subcontract's mags along with the pictures below. Shortly thereafter, Mr. Eric Schellhorn, Director of Sportswear & Accessories, Ruger® Firearms contacted me on 4/30/2018 to discuss my evaluation of the OE brand mags for the Mini I set to Ruger via the ‘Tell the CEO’ link. He informed me that Ruger does not make any of their mags, rather they subcontract them out. I responded to his message with the following:
"Based upon my message it’s clear that I believe that Ruger should review the design, manufacturer, and costing basis of your 20rd mags with your supplier paying special attention to the detail design of the mag lock tab on the rear and the quality of assembly and welding.
Let me suggest that you or your staff purchase some OE Brand 20rd Straight Mini-14 mags from CDNN (quickly before they run out) and evaluate them for their design, quality of manufacture, and costing. I think Ruger and your mag supplier would benefit from reviewing them together."
He responded with a phone call to me where we discussed my testing methods and results, evaluation and conclusions, and other comments. He was very interested in my evaluation of the quality of both mags, both in their design and manufacturing. I again suggested that his staff acquire a few OE mags and do their own testing and evaluation of them. I also mentioned that while the OE brand 20rd mags are every bit as well made, and candidly designed with a better mag catch tab, as Ruger's subcontractor's 20rd mag, the OE brand mag at $14.99, is ½ the price of the going rate of $29.99 for Ruger's mag.
He agreed to look into the OE mags but as of now, a full year later, I've not heard anything, nor seen anything further on the Mini's mags. Below is my pictorial comparison I sent to Ruger between the 2 brands for you to see for yourselves and make your own conclusion.
OE mag on left, Ruger mag on right. Note that the OE mag has a much better mag catch tab that's spot welded in place like the M14/M1A mags while the Ruger mag catch is a thin formed loop:
OE mag on left, Ruger mag on right. Note that the OE mag has a slight roundout at the forward edge of the mag so it feeds the rd more smoothly and also note the quality of the spot welds and forming of the mag body:
OE mag on left, Ruger mag on right. Note that the OE straight mag is slightly more compact than the curved Ruger one. Also note that both mags show the same crisp bends and good manufacturing quality. There is a slight difference in the feed lips, however, my testing revealed no advantage to either design. BTW, the view of the mag catch tab is blocked by the mag body because of the camera angle [my bad]:
