I've searched far and wide for any information about an after market top-end conversion for the Fiveseven to fire .22 Magnum, or .22LR and so far have come up empty. I see plenty of back and forth about whether the .22 Magnum is as potent as the 5.7x28, but all that nonsense aside, if EVER there is a pistol perfectly suited for conversion to .22 Mag the Fiveseven is it! It already has a nifty delayed blowback system that will work for the .22M, or circumvented for straight blowback with the.22LR. Since it uses an inexpensive slide cover, a replacement slide could be fabricated from sheet steel with a steel breech block to handle the firing pin, breech face, and hammer impact face...much the same as how original SIG 9mm slides were made. The poly cover would make it all look factory. A single stack mag could be easily machined from billet...maybe single stack but the POINT of the conversion isn't to replace the capability of the Fiveseven, but to allow shooters the option to shoot lower cost ammo. Of course even with a single stack mag it would still hold as many or more than the Excel .22M auto pistol.
I know it CAN be done, I'm just surprised the aftermarket...and even FNH has not capitalized on the idea. Being able to slide on a conversion top end would be a major value-added selling point of such an expensive pistol. SIG is an example of doing just that, as are the myriad of aftermarket .22LR conversions for 1911's and Glocks. In this regard the Fiveseven is unique in being built to handle the longer Magnum round.
Considering the prices I've seen for aftermarket barrels I'd thing many would be willing to pay $400-$500 for a conversion top end with magazine(s).