SOUND SUPPRESSOR MODEL HDM
P. 3
The original 6¾ inch barrel was reduced in diameter and perforated
with four rows of eleven 1/8 inch holes. The volume between the outside of
the barrel and the approximately eight inch long outer tube was filled with a
stack of brass screen washers to function as a packing material. Forward of
the muzzle was a stack of similar screen washers with a smaller central hole
to pass the bullet extending to the front cap. The intent was to replace the
screen washer packing every 200-250 rounds – a task that was difficult at
the armorer level and impossible in the field. Packing replacement became
almost impossible if the interval extended past 500 rounds.
The outer tube and front end cap were mild steel. Original specimens
were finished with a standard black oxide (“blued”) finish while subsequent
units has a dark grey phosphate (Parkerize) finish.
Various models of the .22 caliber High Standard pistols, including the
H-D Military have been suppressed by a number of manufacturers. One
company, Automatic Weapons Co in New Mexico in the 1980s, built a num-
ber using a shorter tube with a replaceable copper packing material based
loosely on the original OSS design but more similar to their suppression of
the Ruger Mk1 pistol. Although simpler to repack, service was still required
at intervals of 300-350 rounds.
GEMTECH’S HDMs SUPPRESSION OF THE H-D MILITARY
In 2016, the Gemtech custom shop revisited the OSS suppressed H-D
Military pistol with the goal being to develop a highly efficient integrally
suppressed pistol with easily serviced modern parts that required no part
replacement. Further, the requirement was that the cosmetics had to be
such that it was indistinguishable from the original OSS version. The result-
ing design is an improvement on Gemtech’s Quantum integral Ruger MK-2
pistol. While retaining velocity control to permit the use of HV .22LR ammu-
nition, the Gemtech HDM suppressor achieves a sound reduction in excess
of 35 dB as contrasted to the original OSS design of 20 dB. Photographs of
the original and Gemtech replica are on the next page.
AMMUNITION RECOMMENDATIONS
Special barrel modifications allow the use of both standard and high
velocity ammunition, although the use of standard velocity loadings will be
more pleasing. The weapon functions best using Gemtech subsonic .22LR
ammunition with the 42 grain bullet.
