Specifications - Gemtech SFN-57 Operation

SOUND SUPPRESSOR MODEL SFN-57™ (5.7mm)
This suppressor contains no expendable parts and may be cleaned by
immersion in suitable solvents and oils. This instruction manual gives the
necessary instructions for maintenance of this unit.
The real limiting factor on the effectiveness of centerfire rifle suppres-
sors is related to the sound of the bullet in free flight. The free flight bullet
noise is related to the general bullet shape and is also directly proportional to
the bullet velocity, and all the 5.7x28mm ammunition (except the SB-193
Subsonic) is supersonic with significant bullet flight noise. The SFN-57 sup-
pressor is capable of reducing the sound of the muzzle blast to below the
level of bullet and action noise. Because of the sound level of the bullet in
flight, it is not possible to truly appreciate the degree of reduction when the
muzzle blast is reduced to less than the bullet flight noise unless subsonic
ammunition is used.
Besides sound suppression, there are other benefits of a sound sup-
pressor which are seldom mentioned. Sound suppressors are exceptionally
effective flash suppressors. This is an important consideration when used in
the flammable atmosphere often encountered in drug labs.
Construction Materials
At the time of printing of this manual, four types of 5.7 x 28 mm ammu-
nition are produced by FN for the P90 Personal Defense Weapon and the
Five-Seven pistol. The standard SS-190 ball ammunition is supersonic and is
identified by a black tip. The practice ammunition has no markings on the
full-metal-jacketed projectile. The SB-193 Subsonic ammunition is identified
by white marking on the full-metal-jacket projectile. The Tracer ammunition,
L191, is identified with a red marker. All three of these factory rounds are
certified for use by FN in the P90 and all are suitable for use with the SFN-57
suppressor.
Gemtech specifically cautions against the use of non-FN approved am-
munition, and use of such ammunition will void both the warranty issued by
FN as well as the warranty for damage to the suppressor.
The SFN-57 suppressor has been specifically designed for use with the
FN 5.7 x 28 mm cartridge. Use with any larger cartridge, such as the 5.56 x
OVERALL EFFECTIVENESS

SPECIFICATIONS

Length:
Diameter:
Weight:
Muzzle threads
Suppression level:
AMMUNITION
6 in.
1.25 in.
5 oz.
M10x1 (1/2-28 for the SAR-57)
varies with ammunition used
High tensile strength aluminum
P. 5