[mrerick]

I checked around for some background on grips and the potential for damage like this.

The grips were made from a "Z3" phenolic resin based Bakelite which was mixed with wood flour (cellulose) as a filler.

Type Z 3 compounds were materials based on phenolic resins that were heated to 170 degrees Centigrade and pressed under very high pressure in closed molds.

The resin is a fixed setting thermoplastic that should not re-melt after this treatment.

The early grips used on Krieghoff Lugers are noticeably smoother and finer grained than the Mauser grips. Krieghoff probably used a very fine wood flour. The Mauser grips a coarser one.

Sturgess notes: "Mauser pattern, (grips) often show considerable surface roughness or traces of delamination and often swelling on the inner face from movement and water absorption by the laminated paper filler through cracks and surface micro-
porosity."

The most likely cause of the deformation is moisture absorption.

If these flew in the belly of an airplane, and were exposed to surrounding air they were made very cold and dry quickly, then warmed up in what is potentially a moist enviornment. That could lead to uneven absorption of humidity and the warping.