Lots of information in this thread and I felt like I had to read a ton of posts to piece together some information on my recently purchased RIA 51738 (Edge clone type model) to make an informed decision regarding reliable magazines. Just wanted to do a quick re-cap to possibly save people the time and effort of reading all the posts I had to go through in this thread and a couple others.
-The first route where you don't have to mess with anything regarding magazines on this 40 S&W model seems to be to buy the MBX magazines for Para/Armscor. At $130 a piece, that quickly becomes a chunk of pocket change, though a reportedly reliable option. Not a bad choice, but it didn't make sense to me. Seemed silly to buy a "budget" competition gun and then buy a bunch of super expensive magazines.
-The second reliable route seems to be using STI mags, which may or may not work with your factory magazine release, and also becomes expensive fast once you get into tuning and replacing base plates, followers, etc. This was my first inclination. My reasoning was that even though it would ultimately be almost as expensive as the first option, these were magazines that could later be used in any other STI platform if I were to upgrade. Ultimately, I went with the cheaper option to keep some extra money in the budget for any changes/upgrades needed on the firearm itself.
-The third route is basically buying a factory magazine tube and using some form of base plate and follower combination that is reliable. This is the route I took, though it seems like some people's luck has been hit or miss depending on what parts they settled on. I ended up using the ACT P16 magazines from Greg Cote ($22), Taran Tactical Universal STI/SVI Follower ($10), matching Taran Tactical 140mm Spring ($9), and Dawson Precision base plate for Para HiCap ($35) for a total cost of $76/magazine with a 21 round re-loadable capacity. They have been very reliable so far. I did file the protrusion that engages the slide stop off on the follower to improve reliability. Prior to doing so, the mags would occasionally not drop free and it seemed like it was sometimes causing binding within the tube. They seem to be functioning very well now. I've had about 2 failures in roughly 400 rounds, both of which were with my 170PF reloads. Factory loads have been 100%. Thinking that a lighter recoil spring will probably increase reliability with my reloads to 100%.
-I also changed the factory magwell out to the larger Taylor Freelance "Fattie" and it works well with my chosen magazine setup with no modifications.
-Got a Ghost "The One" holster for 1911 & Clones, and it seems to fit great.
I wanted an Edge, but decided to go with the "budget" option for now and am not disappointed since I went into it with the realistic expectation that it would require at least a little bit of work. Have another buddy that wanted an Edge, and has the money for it, that shot the RIA 51738 once and then promptly tried to buy it off of me when he realized that it's hard to find in stock and is really good "bang for the buck".
Happy shooting!