Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: CHAMBERING OF LOW-ENERGY TRAINING AMMUNITION IN
AUTOMATIC FIREARMS
FIELD OF THE INVENTION
This invention relates to the field of firearms and
provisions for modifying semi-automatic firearms for training
purposes. In particular, it relates to reliable chambering in
firearms that have been modified to straight blow-back action
so that they can fire low-energy training ammunition.
BACKGROUND TO THE INVENTION
In military and police firearms applications almost
all of the ammunition consumed is used for training. For some
training purposes, however, normal ammunition is not adequate.
An alternative type of known training ammunition, represented
by United States Patent 5,359,937, fires a low-mass projectile
relying on a special, low-energy cartridge designed to provide
cycling of suitably-modified, recoil-operated automatic
weapons.
An advantage of the low-energy training ammunition
is that it has a shorter range and lower penetration capacity
than standard ammunition. This permits use of smaller, less
secure firing ranges as training facilities. If standard
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ammunition were accidentally employed in these facilities,
unexpected dangers would arise from the increased striking
power and range of such standard ammunition.
The weapon modifications required to permit cycling
while firing low-energy training ammunition generally include
replacing or modifying the barrel, and sometimes replacing or
adding certain other components, depending on the weapon
involved. These modifications also take safety into
consideration. For example, in 9 mm automatic firearms, the
caliber of the substitute barrel may be smaller than the
diameter of the projectiles in standard 9 mm ammunition. If
an attempt is made to chamber a standard round in such a
training-adapted firearm, the design of the chamber and barrel
will not normally permit entry of the standard projectile.
This ensures that such modified weapons cannot fire standard,
live ammunition.
Firearms of other calibers, such as caliber .45, may
also be converted to fire the same low-energy training
ammunition using similar training barrels as for converted 9
mm pistols.
The low-energy cartridge represented by United
States Patent 5,359,937, in combination with a substitute
training barrel, provides recoil actuated cartridge case
ejection through a pure blow-back action. Such a system, when
firing appropriate marking cartridges, makes an effective
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close-range, force-on-force training system. Hits, which are
non-lethal, are denoted by red, blue or other coloured marks.
This system enhances the realism and training value of
interactive scenario tactical training because it allows
trainees to use their service weapons in a representative
manner in exercises simulating, for example,
counter-terrorism, close quarters combat, urban fighting,
protection of dignitaries, trench clearing, and fighting in
wooded areas.
When firing standard ammunition, with its abundant
associated energy, it is necessary in many weapons,
particularly handguns, to lock the barrel to the slide during
the beginning of their rearward motion for a period long
enough for the projectile to exit the barrel muzzle while the
breech is still closed. This allows the chamber pressure to
drop before the breech opens to eject the spent cartridge
case. A locking mechanism couples the slide and barrel
together for the first portion of the recoil, and then
releases the slide. Thus, in such normal weapons, the barrel
recoils, at least partially, with the slide. Upon unlocking,
the slide continues its rearward travel while the barrel stops
in the proper position to receive the next round from the
magazine to be chambered.
In a training barrel it is necessary to omit this
barrel-locking mechanism and, by so doing, the recoil action
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becomes pure blow-back of the slide only. This must be done
because there is not enough energy in low-energy training
cartridges to precipitate sufficient recoil to carry the
barrel and the slide rearwardly in their standard
configurations. A training barrel of the type addressed by
this invention is similar in most aspects to the standard
barrel for a particular pistol which normally relies on a
barrel locking mechanism, but is modified, in part, by
removing this locking mechanism, so that the barrel and the
slide are no longer held together for the first portion of the
recoil cycle.
In some converted pistols, however, after the
barrel-locking mechanism has been removed so that the weapon
can fire low-energy ammunition, as represented by United
States Patent 5, 359, 937, the barrel does not move rearward far
enough, if at all, after firing to be in its normal position
to receive the next round to be chambered. This happens
precisely because the barrel is no longer locked to the slide,
which would normally carry the barrel to the correct position
before unlocking and leaving it there.
It is, therefore, an objective of this invention to
provide a conversion barrel system for this class of firearm
that will contribute to the proper positioning of the barrel
for chambering.
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A way to do this for certain 9 mm pistols, such as
the Walther P-5, has been described in PCT Patent Application
PCT/CA/00174 dated 14 March 1997 and conceived by the same
inventor as herein. This PCT application provides a system for
the positioning of the barrel for chambering by adding a
spring-loaded device to the bottom of the training barrel
which, upon firing of the weapon, positively moves the barrel
rearward to its required position for receiving the next
cartridge from the magazine in a manner which is completely
independent from the motion of the slide. The present
invention does the same thing in part, but in a different
mechanical configuration.
Even if the barrel were carried to its most rearward
position, which is most favourable for chambering of the next
cartridge, trouble-free chambering is not assured because the
motion dynamics of the low-energy training cartridge as it
leaves the magazine and enters the chamber are not the same as
those of a service cartridge. This is due to the much lower
weight of the training cartridge with its paucity of
propellant and thin-walled plastic training projectile.
There is also a difference in weight distribution,
which means that the center of gravity of the low-energy
training cartridge is shifted rearwards compared to standard
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service cartridges with their greater amount of propellant and
heavier metal projectiles. In addition, the external shape of
the low-energy cartridge is not identical to that of service
cartridges, and this too contributes to differences in the
chambering process. The training cartridge may, therefore,
require additional guidance as it moves from the magazine to
the chamber to ensure that it does not jam during this
high-speed transfer involving both vertical and horizontal
movement. The invention herein, in one variant, addresses
this consideration as well by providing a removable feed ramp
extension to the end of the training barrel. The ramp must be
removable with respect to the training barrel because it is
not possible to insert it integrally with the training barrel
without modifying the slide and/or the frame. Such
modifications are not acceptable because the weapon must be
capable of being reconverted back to the firing of service
ammunition by simply removing the training barrel and
reinserting the service barrel.
A second objective of the invention, therefore, is
to provide a supplementary, moveable feed ramp between the
magazine and the entrance to the chamber that will greatly
increase the probability of proper chambering of the next
low-energy training cartridge to be fired.
A way to do this for certain 9 mm pistols, such as
the Sig 225, has been described in United States Patent
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6,276,252 issued 2 August 2001, as conceived by the same
inventor. This application describes a system for ensuring
proper chambering of low-energy training ammunition, as
represented by United States Patent 5,359,937, by fitting a
removable ramp extension to the chamber end of a Sig 225
training barrel, such extension extending rearward towards the
top of the magazine in such a fashion as to allow smooth
passage from the magazine to the chamber of the next round to
be fired. The present invention does the same thing in part,
but by means of a different mechanical configuration.
The invention in its general form will first be
described, and then its implementation in terms of specific
embodiments will be detailed with reference to the drawings
following hereafter. These embodiments are intended to
demonstrate the principal of the invention and the manner of
its implementation. The invention in its broadest and more
specific forms will be further described, and defined, in each
of the individual claims which conclude this specification.
SUMMARY OF THE INVENTION
This invention is directed to an automatic pistol
adapted to fire low-energy training ammunition wherein a
training barrel that omits the barrel-locking feature normally
present is substituted in place of a standard service barrel.
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The invention firstly provides a system for the positioning of
the training barrel for chambering by adding a spring that
bears on the barrel which, upon firing of the weapon,
positively moves the barrel rearward to its required position
for receiving the next cartridge from the magazine. This
occurs in a manner which is completely independent from the
motion of the slide. Without this positioning mechanism, the
training barrel would be too far forward from the top of the
magazine and the incoming cartridge would not necessarily
enter the chamber cleanly, hence provoking a weapon jam
whenever such misalignment should occur.
According to one aspect of the invention, a firearm
is provided with a slide and a training barrel which at no
time are locked together during the firing cycle, and the
training barrel is provided with a downwardly protruding lug
preferably located under the chamber. In one variant this lug
has two legs which longitudinally straddle a slide lock lever
located transversely in the frame of the firearm and limit
longitudinal motion of the barrel in at least one direction.
The firearm to which this invention is applicable is
conventionally provided with a recoil spring which extends
between the frame at its rearward end, and the slide at its
forward, muzzle end. This recoil spring is conventionally
located over a recoil spring guide rod aligned at its forward
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end by the slide and thrust rearwardly at its rearward end by
the recoil spring to rest against the frame.
According to the invention, the recoil spring guide
rod is provided at its rearward end with a small barrel
positioning spring, nested within its core and acting along
the same axis as the recoil spring, but passing above the
surface of the frame to bear against the forward facing
surface of the front leg of the training barrel lug.
When the weapon is in-battery and ready to fire, the
barrel positioning spring is at maximum compression because
the slide has pushed the training barrel to its farthest
forward position during chambering of the low energy cartridge
to be fired. When firing occurs, the slide recoils without
pulling the barrel back with it. Even though there is nothing
obstructing rearward movement of the barrel after the slide
has recoiled, the barrel would normally not move rearwardly
without the barrel positioning mechanism of the invention
being present.
Rearward motion of the training barrel is effected
by the barrel positioning spring as it bears on the forward
facing surface of the front leg of the barrel lug, its spring
force being expressed in the rearward direction because the
recoil spring guide rod does not move relative to the frame.
Travel of the barrel with respect to the frame is
limited by the combination of a slot present in the lower end
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of the barrel lug and a transverse pin mounted in the frame --
conventionally, the "side lock lever"-- which passes through
the slot. This slot is bounded by the two downwardly directed
legs that are extensions of the barrel lug. When the pistol
is in-battery the slide lock lever restrains the frontward
facing surface of the rear leg of the barrel lug, and when the
slide is at its maximum rearward position the rearward facing
surface of the rear leg of the lug is restrained by the frame,
thus limiting rearward travel of the barrel. The latter
configuration places the barrel at its most favourable
position relative to the magazine for facilitating
trouble-free chambering of the next round to be fired.
The mechanical characteristics of the barrel
positioning spring in compression must be such that the spring
will be capable of readily lengthening from its compressed
state to move the barrel positively back to the required
position for receiving the next round. The barrel is free to
move rearwardly only while the slide is displaced rearwardly
in its recoil cycle. The barrel positioning spring is only
partially extended after rearward travel of the barrel ceases,
providing a residual rearwardly-directed force so that the
barrel will not move forward again until the slide of the
weapon commences to chamber the next cartridge. Since the
strength of the barrel positioning spring is much less than
the strength of the recoil spring associated with the slide,
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the motion of the slide will not be impeded as it returns to
close the chamber and push the barrel forward in preparation
for firing of the next round. In doing so, this action of the
slide recompresses the barrel positioning spring, readying it
for the next cycle, as well as advancing the barrel to its
forward, in-battery position.
As a further feature of the invention, an additional
element for ensuring proper chambering of ammunition is
provided by fitting a removable ramp extension to the chamber
end of the training barrel. The bottom lip of the barrel
chamber is slightly dished at the chamber entrance to form a
normal feed ramp. The extension ramp is mounted on the frame
and is directed rearwardly towards the top of the magazine to
allow smooth passage from the magazine to the chamber of the
next round to be fired. Without this ramp extension, the
barrel chamber, even after being optimally positioned
rearwardly by the barrel positioning spring, as described
above, may be positioned too far from its standard position
adjacent to the top of the magazine and the incoming cartridge
may not necessarily enter the chamber cleanly, thereby having
the potential to jam the weapon.
In the case of the Colt .45 caliber 1911 automatic
pistol the feed extension ramp is fitted onto the frame and
engages with the downwardly protruding lug under the chamber
of the barrel by a sliding fit. The feed extension ramp in
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this case is provided with two forwardly facing arms,
respectively slidingly fitted into longitudinal grooves formed
on the right and left sides of the lug. The forwardly facing
arms of the feed extension ramp position the upwardly facing
guide surface of the ramp extension in line with the chamber.
The extension ramp serves to fill the gap between the top of
the magazine and the entrance to the chamber when the barrel
has travelled to its most rearward position under the
influence of the barrel positioning spring. When chambering
of the next round to be fired occurs, the round is guided into
the chamber by the extension as the slide moves forward into
the firing position.
No modification is effected to either the slide or
the frame. The feed ramp extension is removable and can be
installed in some firearms by inserting (e.g. by first press
fitting) it into the frame prior to the slide/training barrel
assembly being attached to the frame. Upon assembling of the
barrel into the frame, the feed ramp is seated so that it is
aligned with the barrel, beneath the chamber.
The foregoing summarizes the principal features of
the invention and some of its optional aspects. The invention
may be further understood by the description of the preferred
embodiments, in conjunction with the drawings, which now
follow.
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SUMMARY OF THE FIGURES
Figure 1 is a partial cutaway, cross-sectional
side-view of a caliber .45 pistol modified to fire low-energy
ammunition, as represented by United States Patent No.
5,359,937, with a fully-chambered low-energy cartridge.
Figure 2A is a side view of the 9 mm training barrel
used in the modified caliber .45 pistol of Figure 1 in
combination with its recoil spring, recoil spring guide rod
and barrel positioning spring.
Figure 2B shows a cross section of this barrel at
the point where the barrel positioning spring passes above the
frame to contact the barrel.
Figure 2C is a perspective view showing details of
the recoil spring guide rod with the barrel positioning spring
in place.
Figure 3 shows the pistol of Figure 1 after firing
with the slide in its most rearward position, ready to be
moved forward by the recoil spring. The spent case from the
chambered low-energy training cartridge of Figure 1 after
firing has been ejected from the weapon and the next cartridge
from the magazine is in position to be chambered by the
returning slide.
Figure 3A is a cut away section of the weapon
showing the next cartridge to be chambered in relation to the
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feed ramp extension just after the slide begins to move
forward.
Figure 4A is a side view of the 9 mm training barrel
used in the modified caliber .45 pistol of Figure 1 in
combination with its removable feed ramp extension and its
position relative to the slide lock lever when in-battery.
Figure 4B depicts the feed ramp extension in
perspective view.
Figure 4C is a partial end view showing the grooves
in the barrel lug into which the arms of the feed ramp
extension are slidingly fitted.
Figure 4D shows the barrel of Figure 4A and its
position relative to the slide lock lever when the barrel is
in its most rearward position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 a 9 mm training barrel 1 is shown
mounted in a standard .45 caliber slide 2 which is assembled
to a standard .45 caliber frame 3 so that the converted weapon
will fire low-energy training ammunition 4, as represented by
United States Patent 5,359,937, loaded from 9 mm training
magazine 5. Recoil spring guide rod 6, upon which recoil
spring 7 is mounted, is firmly anchored between the slide-
mounted barrel bushing 8 at the muzzle end and shoulder 9 of
frame 3 such that recoil spring guide rod 6 is immobilized
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with respect to frame 3 by the pressure that the recoil spring
7 applies to the flange 6A on the guide rod 6. Enlarged
flange 6A on the guide rod 6 abuts the shoulder 9 on the frame
3 to effect this immobilization.
Figures 2A, 2B and 2C show barrel positioning spring
seated and carried within a bore 6B in the rearward end of
recoil spring guide rod 6. The protruding end of this spring
10 bears against the forward facing surface of barrel lug 11.
Barrel positioning spring 10 and recoil spring guide rod 6 are
10 assembled by loosely inserting the positioning spring into the
hole 6B drilled in the rearward face of the guide rod.
Positioning spring 10 is then compressed by spring guide rod
6 as the sub-assembly, spring 10 and rod 6 (Figure 2C) , is
pushed into place against the forward face of lug 11.
The weapon configuration in Figure 1 is in-battery
with recoil spring 7 at maximum extension and barrel
positioning spring 10 in maximum compression. When
in-battery, training barrel 1 is in its most forward position
with the forward facing surface of rear leg 12 of barrel lug
11 abutting transverse slide lock lever 13 mounted in frame 3.
Rearward movement of training barrel 1 from its
forward position after firing is effected by barrel
positioning spring 10, which is in compression at the time of
firing. Since recoil spring guide rod 6 does not move
relative to frame 3, barrel positioning spring 10 is
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constrained to expand rearward only. As soon as slide 2 has
completed its initial movement rearwardly (under the influence
of the expanding cartridge case as detailed in U.S. patent
5,359,937) the training barrel 1 is unfettered because the two
components are not locked together. At this moment the
rearward-directed force provided by compressed barrel
positioning spring 10 pushes training barrel 1 rearwardly
until the barrel 1 is brought to a stop when the rearward
facing surface of rear leg 12 of barrel lug 11 abuts frame 3,
as illustrated in Figure 3. Training barrel 1 is thus at its
most rearward position with the entrance to chamber 16 being
located just above and forward of the top of magazine 5. This
is the preferred position for receiving the next round to be
chambered from magazine 5.
The forward motion of slide 2, which first chambers
the next training cartridge 4 to be fired, then picks up
training barrel 1 in the normal manner of the firing cycle
(Figure 3A) and moves it forward to the in-battery position
ready for firing of the next round. This compresses the
barrel positioning spring 10 and readies it for the next
cycle, as shown in Figure 1.
Also shown in Figure 1 is feed ramp extension 14,
which is separately inserted into and rigidly held by frame 3.
Arms 17 of the feed ramp extension slidingly fit around barrel
lug 11 as depicted in Figures 4A, 4B, 4C and 4D. Feed ramp
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extension 14 is a separate piece, non-integral with barrel lug
11, because the training barrel 1 and feed ramp extension 12
cannot be otherwise assembled into the weapon without
modification to either or both of slide 2 and frame 3.
In Figure 4A training barrel 1 is in the in-battery
position relative to slide lock lever 13, as described above
and also shown in Figure 1. After firing, when training
barrel 1 is in its most rearward position, the relation of
slide lock lever 13 to training barrel 1 is shown in Figure
4D, again as described above and also shown in Figure 3.
Figure 4B depicts feed ramp extension 14 with arms 17 at its
forward end and upwardly facing guide surface 18 at its
rearward end. Barrel 1 is able to move relative to feed ramp
extension 14 because grooves 19 formed in the sides of lug 11
are slidingly fitted between arms 17 of feed ramp extension
14, as shown in Figure 4C. Feed ramp extension 14 may be made
of tempered steel.
The presence of feed ramp extension 14 may be
required even after barrel positioning spring 10 has placed
training barrel 1 in the most favourable rearward position as
possible for chambering of the next low-energy cartridge 4, as
described above and illustrated in Figure 3. The gap between
the entrance to chamber 16 and the nose of projectile 20 of
low-energy cartridge 4 may still be too large for reliable
chambering without the presence of feed ramp extension 14,
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which fills the gap, as shown in Figure 3. The next
low-energy cartridge 4 from magazine 5 will, therefore, be
smoothly guided by upwardly facing guide surface 18 of feed
ramp extension 14 into chamber 16 when slide 2 moves forward
to its in-battery position of Figure 1 . This action is shown
in Figure 3A wherein the returning slide has advanced the
cartridge 4 into contact with the ramp extension 14.
The functioning of the combination of the subject
barrel positioning mechanism and subject ammunition loading
mechanism has been tested many hundreds of times with complete
success and reliability in Colt .45 1911 pistols converted to
fire 9 mm low-energy training ammunition as represented by
United States Patent 5,359,937. Individually or in
combination, these two mechanisms are also applicable to other
semi-automatic firearms that fire low-energy ammunition,
including blanks.
CONCLUSION
The foregoing constitutes a description of specific
embodiments showing how the invention may be applied and put
into use. These embodiments are only exemplary. The
invention in its broadest and more specific aspects is further
described and defined in the claims which now follow. These
claims, and the language used therein, are to be understood in
terms of the variants of the invention which has been
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described. They are not to be restricted to such variants,
but are to be read as covering the full scope of the invention
as is implicit within the invention and the disclosure that
has been provided herein.
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