John Martz Custom P38 .45 ACP

John Martz built his reputation on conversions that most gunsmiths wouldn't attempt, and this Walther P38 reworked to fire .45 ACP sits right in the heart of that legacy. The slide carries his signature roll mark, MARTZ 45, alongside a low hand-stamped build number that tells you exactly where it falls in his small run of these guns. That marking matters. Martz worked alone, by hand, and the number of .45 caliber P38 conversions he completed can be counted without much effort.

Look past the familiar P38 outline and the differences pile up fast. The original 9mm chambering is gone, replaced by .45 ACP, which meant reworking the locking block, the breech face, the slide, and the frame geometry to handle a fatter, slower cartridge through Walther's falling-block locking system. The barrel runs long, well past the standard 5 inch service length, finished in a satin steel tone that contrasts against the darker frame. It dominates the profile and shifts the balance forward.

The metalwork shows the hand of someone who cared about fit. Brushed surfaces, crisp machining lines, and tight tolerances throughout. The slide retains the P38 and Walther markings up front, and the controls stay true to the original layout: the slide-mounted safety and decocker, the open-top slide, the familiar trigger and hammer. The checkered black grips wear the Walther banner medallion. There's honest handling wear on the high edges and light age marks across the steel, the kind you'd expect on a working custom piece rather than a safe queen.

For the collector who chases Martz's work, the appeal is straightforward. These were one-man creations, never produced in volume, and a .45 ACP example with a clear build number is the sort of thing that doesn't surface often. This one earns its spot on the strength of who made it and how few exist.