RedBall Sports makes high capacity magazines for Hi-Point pistol caliber carbines. Earlier TFB reported about their 9mm magazines and recently the company announced that they are now making .45 ACP magazines for Hi-Point 4595TS Carbines.
Arguably one of the most significant drawbacks of the Hi-Point carbines are the single stack magazines. Having a pistol caliber carbine with only a 9-shot magazine is not fun, neither practical. That’s why RedBall Sports 20 round magazines can be a really good addition to these guns. RedBall magazines are not simply extended versions of the Hi-Point single stack magazines but they become double stack outside the grip. This allows having a shorter magazine length compared to if it was a completely single stack one.
These RedBall Sports magazines are made of steel. They are heat treated and have a black oxide finish. The polymer part at the middle portion of the magazine is probably designed to provide a stopping point on the magazine well of the carbine. That middle polymer part is not a coupler. The magazine has a single piece construction.
Right now these magazines are available for preorder on the company’s website. The MSRP is $27.99. The orders will start shipping by March 30, 2018.
I think if the company has figured out how to make such magazines (long single stack portion transitioning into a double stack) work reliably, then they should also make them for single stack subcompact pistols. Imagine this kind of extended magazine for a Glock 43 (or any other similar pistol) which will become double stack outside of the grip. That probably would be similar in thickness with the grip and would provide a full-size grip. That way you could carry the handgun with its original magazine for the sake of concealability and have such an extended one (say of 12 or 15 round capacity) for the reload in case if you need more than 6 rounds in a defensive situation.