Slightly off but still relevant to this magazine size discussion. Avery long time ago a US gunsmith named Hoyt got a bug in his head to make .45 ACP match pistols out of Luger P08s. It was a cute but impractical solution to a non-problem (many other smiths had figured out how to make the magnificent 1911 perform). He basically welded up, ground, and hardened feedlips on the pistol frame, cut off magazines an inch or so above their base and crimped the spring with follower into it. You loaded your five rounds by pulling the mag, turning the pistol upside down and carefully dropping the rounds into the open frame, then reinstalling the mag base follower unit. Naturally it also had a twelve inch match barrel with mounted sights. I handled one about fifty years ago but never shot it. The owner said it was extremely accurate but the loading procedure was so slow he was constantly hassled by range officers and fellow competitors during timed and rapid stages. It was a design that I also heard of being tried on converting an S&W M41 to the .32 s&w long. The case for Hoyt was the width of the round, and while sawing a Luger down the midline and weeding in spacing had been done before, his solution was actually simpler and cheaper by far. He built an unknown number of them, but are so rare that the prices become astronomical. The idea might work for this long round, but I think just loading the bullet deeper is really the solution.
cheers. Dr Jim