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Oct. 15, 1946;
w. A. SCHAICH’ ,
Filed Sept. 5. 1944
Wilbur A- ?chnl' Ch
Patented Oct. 15, 1946
Wilbur A. Schaich, Spring?eld, Mass.
Application September 5, 1944, Serial No. 552,784
1 Claim.
(01. 42-3)
(Granted under the act of March 3, 1883, as
amended April 30, 1928; 3'70 0. G. 757)
The invention described herein may be manu
factured and used by or for the Government for
governmental purposes, without the payment to
me of any royalty thereon.
duration is sufficient to carry the breech mech
anism to its full recoil position. For example, in
the U. S. carbine caliber .30 M1, the operating
slide is accelerated by the piston to a maximum
This invention relates to a gas system for a
?rearm and particularly to a mechanism for de
velocity of from thirty to forty feet per second,
which velocity is gradually reduced during the
riving motive power from the gases developed
recoil travel of the slide by the energy required
to open the bolt, extract the case, and compress
cure automatic operation of the breech mech
the driving spring, to a value of from six to ten
10 feet per second at full recoil position. This repre
While not limited thereto, this invention is
sents a substantial range of velocity change dur
particularly applicable to ?rearms wherein the
ing the operating cycle and naturally requires
gas port in the barrel is located close to the
higher shock and fatigue resistance properties in
chamber end of the barrel, resulting in the ap
the moving parts.
plication of gases of extremely high pressures to
Accordingly, it is an object of this invention to
within the barrel of an automatic ?rearm to se
the gas system. Speci?cally a gas system in ac~
provide an improved gas system for an automatic
cordance with this invention may be applied to
?rearm particularly adaptable for operation by
an automatic ?rearm similar to the U. S. carbine
high pressure gases.
A further object of this invention is to provide
caliber .30 M1.
The location of the gas port as near as possible 20 a gas system for an automatic ?rearm which is
to the chamber end of the barrel is obviously de~
sirable from the standpoint of reduction in
length, and hence weight, of the operating rod
self compensating with respect to variations in
pressure of the operating gases supplied, to the
member which transmits force received from the
Another object of this invention is to provide
gas system to the breech mechanism to accom 25 a gas system for an automatic ?rearm wherein
plish the conventional functions of an automatic
the gases are permitted to operate on a moving
breech mechanism, namely, unlocking of the
piston by expansion rather than by an impact
breech, extraction and ejection of the ?red case,
and the loading of a fresh cartridge. With con
gases is substantially increased.
ventional gas systems however, utilizing merely 30
blow and wherein the duration of action of the
A particular object of this invention is to pro
a piston and cylinder, and with the piston ar
vide an improved gas system which may be ap-_
ranged to receive the direct impact of the gases,
plied to an automatic ?rearm similar to the U. S.
such location of the gas port produces at least
carbine caliber .30 Ml which will substantially
three well recognized undesirable features, First,
reduce the maximum velocity of the moving parts
the action of the gas on the piston is extremely 35 of the breech mechanism and which will sub
violent and of very short duration thereby pro
stantially increase the time elapsing between ?r
ducing an undesirably high acceleration of the
ing of the cartridge and opening of the breech
piston and the breech mechanism with accom
panying breakage of parts after a few hundred
The speci?c nature of the invention as well as
rounds. Secondly, it is well recognized that the
other objects and advantages thereof will clearly
pressures developed by successive rounds of am
appear‘ from a description of a preferred em
munition normally depart from the average pres
bodiment as shown in the accompanying draw
ing in which:
sure by a substantial margin. Accordingly, a
round developing slightly higher pressure would
Fig. 1 is an elevational view, partly in section,
accelerate the piston and breech mechanism at 45 of the elements of the improved gas system as
an even higher rate than would a normal round
sembled to a ?rearm.
and in many instances would cause the breech
Fig. 2 is a sectional view taken along the plane
2-2 of Fig. 1.
mechanism to open while the pressure in the bar
rel was above the value generally recognized to
Fig. 3 is a sectional View taken along the plane
be safe for opening of the breech. Thirdly, the 50 3—@ of Fig. 1.
short duration of the force exerted by the gases
Fig. 4 is a sectional View of the cylinder mem
on a conventional piston required the accelera
tion of the breech mechanism to a velocity su?i
Referring to Fig. l a gas cylinder bracket I0
ciently high to insure that the kinetic energy
is shown secured to a barrel l in the vicinity of
imparted-to the breech mechanism in such short 55 a gas port 2. The bracket [0 may comprise either
a separate member slipped over the barrel or
may be integrally formed with the barrel. In
the depending portion of bracket it) a longi
tudinal hole ll is drilled parallel to the axis of
the barrel. A tubular gas cylinder element 20 is
inserted into the hole H and retained therein by
any suitable means, preferably by a press ?t
ume and hence the gases must ?ll such volume
before being effective to move the piston 33
Thus one element of delay is in
troduced in the initiation of movement of pis
ton 30.
When piston 3H begins to move rear
wardly, the eifect is to misalign piston port 34
with cylinder port ‘24 and in effect cut off the
entry of further gases into the gas system and
engagement. A radial collar 25 on the rear end of
trap the gases which have already entered the
gas cylinder 29 bottoms against the rear wall
system. Further action of the gases upon the
of bracket m, The top surface of the collar 2! 10 piston is then dependent upon the expansion
is provided with a ?at portion 22 which snugly
of the gases and accordingly a very uniform ac
engages a correspondingly flat surface 3 provided
celerating force is applied to the piston 39, Ex
on the bottom of barrel l and thereby serves to
pansion of the gases will continue until the ports
prevent rotational shifting of the gas cylinder
35 pass rearwardly out of the end of cylinder 23
20 with respect to the bracket H3. As previously
whereupon the gases will be exhausted to atmos
mentioned the gas cylinder 28 is hollow and de
phere. A power stroke of any desired length may
?nes a gas chamber 23 which opens from the
obviously be obtained by increasing the spacing
rear of gas cylinder 2%. A gas port 24 is provided
between the rear end of cylinder 25 and the loca
thru bracket ii! and gas cylinder 20 at a position
tion of cylinder port 24. It is generally desirable
to align with the end of barrel port 2. The port
to have the power stroke substantially less than
24 is preferably made substantially larger than
the recoil movement of the breech operating
port 2 in order to compensate for any. slight mis
member in order that exhaust of the gases will
alignment of parts in assembly. A cylindrical
occur at a substantial pressure, thereby insuring
piston 36 snugly engages the interior cylindrical
surface of gas chamber 23. The periphery of 25 that carbon and other combustion products will
be blown out of the piston and cylinder chambers.
piston 36 is provided with a plurality of annular
When a gas system constructed in accordance
gas recesses 3i which in effect produce a gas
with this invention was applied to a gun similar
seal between the exterior of the piston 38 and the
to the U. S. carbine, caliber .30 M1, the maximum
interior of the gas cylinder 26. Piston 30 is also
partially. hollow, being provided with an axial 30 velocity attained by the moving parts in their
recoil stroke was not over twenty feet per second.
hole 3.‘: opening from the forward end of the
Furthermore the time elapsing between the ?ring
piston. The rear end oi’ piston SS is solid and is
of a cartridge and the opening of the breech
arranged to lie in abutment to breech operating
mechanism was more than doubled. Thus a gas
member 49. Operating member Kit is suitably
system construction in accordance with this in
connected to the breech mechanism (not shown)
vention not only insures longer life of moving
of the ?rearm and arranged to reciprocate and
parts of the ?rearm by decreasing shock and
thereby impart the necessary movement to such
fatigue effects but in addition provides a sub
breech mechanism to produce automatic opera
stantial increase in delay of breech opening,
tion of the weapon. In the speci?c application
thereby insuring opening of the breech mecha
of this invention to the U. S. carbine caliber .30
nism when the pressure remaining in the bar
M1, breech operating member llB comprises the
rel does- not exceed that known in the art to
standard operating rod of such weapon.
be most desirable for opening of the breech and
It should be understood that the full recoil
extraction of the ?red case. It is obvious that a
stroke of operating member to is preferably less
than the length of piston 38 which is inserted 45 gas system constructed in accordance with this
invention is very adaptable to large production
within gas cylinder 2!), thus insuring that piston
manufacture inasmuch as all the principal parts
30 is engaged in gas cylinder 28 during normal
are tubular.
operation of the ?rearm in all positions of the
I claim:
operating member 46. Hence no stops are needed
to retain piston 35 within gas cylinder 20. An op 50 In an automatic ?rearm having a barrel with a
gas port therein and a reciprocating breech op
erating spring 53 is provided to return operating
erating member. the improvement comprising
member Gil to its battery position, and piston 3i)
a gas cylinder secured to the barrel in the vicinity
is in turn returned to a position Within gas cylin
of the barrel gas port, said gas cylinder de?ning
der it! where the forward end of piston 33 bottoms
against the base of gas chamber 23. An annular 55 a rearwardly opening, cylindrical chamber dis
posed parallel to the path of movement of said
recess 33 is provided about the periphery of piston
breech operating member, a cylindrical piston
30 in such position as to lie adjacent to cylinder
slidably and rotatably mounted within said cyl
port 24 when piston 38 is in its battery position. A
inder chamber, said piston having a forwardly
plurality of radial ports 31% are provided, passing
opening hollow portion, the rear end of said
thru the wall of piston 38 and located in the
piston arranged to abut the breech operating
center of annular recess 33. Ports 35 thus assure
member to impart rearward movement thereto,
passage of the gases into the hollow portion 32 of
said cylinder having a gas passage therein com
piston 33 independent of the relative angular
municating between the barrel gas port and the
position of piston 39 with respect to gas cylinder
In operation, a cartridge is ?red and the bullet
is driven thru the bore by the gases thus formed.
After the bullet passes the barrel port 2, a por
tion of the gases are diverted thru the barrel
65 interior of said cylinder chamber, said piston
having a reduced diameter annular groove on
its periphery located in substantial alignment
with said gas passage when said piston is in its
forward position, said piston having at least one
generally radial hole in said reduced diameter
port 2, the cylinder port 24, and the piston ports 70 annular
groove, communicating with the said
' 36 into the hollow interior 32 of piston 30. The
of said piston.
hollow interior 32 is of appreciable volume but
preferably less than 25% of the barrel bore vol
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