7.5mm SIG Stgw.57
assault rifle as used by Swiss army, right side, with bipod attached to
forward position
7.5mm
SIG Stgw.57 assault rifle as used by Swiss army, left side, with folded
bipod attached to rearward position
Semi-experimental 7.62x39
SIG 510-3 assault rifle as made for Finnish army assault rifle trials
in late 1950s
7.62x51 NATO SIG 510-4
assault rifle, as made for export
7.62x51 NATO SIG AMT
semi-automatic rifle, as made for civilian sales
Caliber:
7.5x55 mm GP11 (Stgw.57) or
7.62x51mm NATO (SIG 510-4) Action: roller retarded blowback Overall
length: 1105 mm (1016 mm SIG 510-4) Barrel length: 583 mm (505 mm SIG 510-4) Weigth: 5.56 kg empty (4.25 rg empty SIG 510-4) Magazine capacity: 24 rds (20 rds SIG 510-4)
Switzerland began to experiment with intermediate
cartridges before the World War 2 and, being a neutral
country, closely watched the developments made during and after the
war. Being entirely satisfied with the power and accuracy of its 7.5 mm
GP11 (7.5x55) cartridge, the Swiss army tried to achieve a full power
selective-fire rifle. After a couple of false starts, first with the
gas-operated Sk-46 self-loading rifle, and secondly with the most
unusual AK-53 blow-forward design, the famous SIG company finally
produced a weapon which satisfied the Army in 1955. This was
the 7.5 mm AM-55, a retarded blowback design, developed under the
leadership of the Rudolf Amsler. The basic principles of the action
were borrowed from German WW2 period Mauser 'Gerät 06H' and Stg.45(M)
assault rifles, but with much altering involved. In 1957 the Swiss army
adopted the AM-55 as the Schturmgewehr-57, or Stgw.57 for short. Made
between 1957 and 1983, the Stgw.57 represented one of the finest and
most expensive automatic rifles ever issued to any army in the world.
Chambered for full power 7.5 x 55 GP11 ammunition, the Stgw.57 provides
long range accurate shooting in semi-automatic mode, necessary for the
typical Swiss mountain country, in combination with significant full
auto firepower, thanks to its relatively heavy weight, integral bipod
and a shrouded barrel. In the modified form, known as the SIG-510, this
design was relatively successful, being sold to various South American
countries, most notably Bolivia and Chile, chambered for 7.62 mm NATO
ammunition.
The action of the Stgw.57 was derived from the
roller-retarded blowback system originated by Mauser engineers in
Hitler’s’ Germany. However, the Swiss designers replaced the rollers
with the roller-shaped pivoting flaps, interposed between the bolt head
and the bolt body. The receiver is made from stamped steel, with a
separate trigger unit housing made integral with the pistol grip frame
and trigger guard. The fixed barrel has a perforated steel jacket with
two mounting points for an integral bipod – one near the muzzle, and
another near the receiver. The front part of the barrel is exposed to
act as a rifle grenade launcher. To smooth out the excessive recoil
generated in full automatic fire, and especially by rifle grenades, the
fixed butt-stock is fitted with a recoil buffer. The safety / fire mode
selector is located at the left side of the trigger unit. Stgw.57 is
fitted with large, T-shaped charging handle and with the folding
“winter trigger”, which, when unfolded, extends down below the trigger
guard, enabling the rifle to be used in arctic mittens. Since the
Stgw.57 was designed with the so-called straight-line layout, the
raised sights are mounted on high, folding bases, with the rear sight
being micrometer-adjustable from 100 to 650 metres. The Stgw.57 also
could be fitted with the special Kern 4X telescope sight. Stgw.57 is
fed from curved box magazines, made from steel and containing 24
rounds. The small forend is made from plastic and the gun is fitted
with a side-folding carrying handle. Other accessories include the
sling, the bayonet, and a special small-capacity magazine for blank
grenade-launching cartridges. Export military versions of the
Stgw.57, known as SIG SG-510, were made in 4 basic modifications, of
which only one was made in any significant quantities, the SG-510-4.
This was chambered in 7.62 x 51 NATO, had a shorter barrel, and
non-folding aperture sights. The forend and buttstock were made from
wood. Other versions included the SG-510-1 (exactly the same
rifle as the Stgw.57), the SG-510-2 (a lightweight modification of the
Stgw.57, also in 7.5 mm), and the more compact SG-510-3, chambered for
the Soviet 7.62 x 39 cartridge (produced in late 1950s for assault
rifle trials in Finland). Civilian semi-automatic only versions of the
Stgw.57 were designated as PE-57 (in 7.5 mm GP11) and SIG AMT (a
semi-auto version of SG-510-4 in 7.62 mm NATO).