I believe my G42 is a new updated model, and it came with “03” magazines. It only experienced some initial hiccups with super weak and inconsistent Freedom Munitions XTP ammo I bought right before they went belly-up (while using the original unmodified factory magazines). But I haven’t had any malfunction with other premium self-defense ammo (e.g., Speer GD, Fiocchi XTP, Underwood +P GD, XTP and GS) and inexpensive range ammo (e.g., CCI Blazer Brass and Aluminum, Remington/UMC, PMC Bronze, FM 100gr reman) that I have ever shot using MagGuts+1 and Vickers Tango down +2. I’m also using the DPM recoil reduction system in my G42, and I have not had a single malfunction of any kind with these mag. extensions and the the DPM systems in my gun. My baby Glock is as reliable and accurate as my other Glocks. It is also a very soft shooter. I really like it.