Rifle-firable training grenade and rifle-grenade firing instruction system

Completely inert training grenade intended to be fired by a rifle and a propellant cartridge, comprising a metal tube (1) equipped with a rear stabilizing tail unit (2) and with a front solid part (3) which closes off the tube. This front part (3) carries a hollow nose (4) containing a marking substance (5), this nose (4) being fastened removably by engagement to the front solid part (3) of the tube. The nose (4) is sufficiently resistant to withstand the shot, but is destructible on impact. The solid front part (3) of the tube is produced in one piece with the tube, the diameter of this part being substantially equal to or slightly larger than that of the rest of the tube. The nose (4) engaged on this solid front part has an inner annular shoulder (11) bearing on the front surface (3a) of the solid part (3) of the tube, and the front end of the nose (4) is flat. The nose (4) is shaped so that its wall can break in the event of its impact on the ground.

The present invention relates to a training grenade intended to be fired by 
means of a rifle. Such a completely inert grenade comprises a metal tube 
equipped with a rear stabilizing tail unit and with a front solid part 
which closes off said tube, this front part carrying a hollow nose 
containing an inert marking substance. 
The marking substance contained in the hollow nose can be plaster, barium 
sulfate or any other powdery or liquid product. 
The invention is also concerned with a rifle-grenade firing instruction 
system comprising the above-mentioned training grenade and its associated 
launching cartridge. 
In known embodiments, the nose is fixed to the metal tube which is commonly 
called a sleeve tube or fusion ball. 
On impact, the nose is destroyed and the marking substance gives a visual 
indication of this. 
There are known training grenades comprising a sleeve tube the interior of 
which has a bullet trap absorbing the bullet from a live cartridge and 
which also require the addition of propellant powder. 
Both this bullet trap and the powder are destroyed at each firing, and 
therefore no part of these grenades is recoverable. 
Such training grenades are consequently costly. 
Moreover, such training grenades, because they require the use of live 
cartridges for firing them, present a danger to the training personnel and 
need very large safety clearances for the firing range. 
On the other hand, there are known training grenades which can be fired 
with propellant, that is to say blank, cartridges, but these grenades are 
equipped with a pyrotechnic marker. 
These grenades thus avoid the abovementioned dangers associated with the 
use of live cartridges. 
However, these training grenades too are not recoverable, in so far as the 
pyrotechnic marker has to be reloaded, thereby likewise making them very 
expensive and moreover risking causing fires in summer in the brush of the 
firing ranges. 
Furthermore, these grenades are fired by means of a propellant cartridge 
which does not have the external shape of a true live cartridge, and 
therefore they cannot be used in the loaders of automatic rifles and do 
not ensure an automatic re-cocking of these rifles. 
U.S. Pat. No. 3,156,187 makes known a training grenade, of which the hollow 
nose containing the marking substance is engaged on a rubber block of wide 
cross-section which is fastened to the front of the tube. 
The nose terminates in a rounded tip. This nose has a conical shape of 
relatively high angle, so that, in the event of an impact occurring at a 
low angle of incidence, this nose risks not being broken. In this case, 
the location of the impact is not marked. 
The object of the present invention is to provide a training grenade, the 
nose of which is capable of breaking, even in the event of an impact of 
very low incidence and on very loose ground, without the solid front part 
of the tube risking being damaged under the effect of the shock after the 
destruction of the nose. 
The invention is thus aimed at a training grenade intending to be fired by 
means of a rifle and of a propellant cartridge, this grenade comprising a 
metal tube equipped with a rear stabilizing tail unit and with a front 
solid part which closes off said tube, this front part carrying a hollow 
nose containing a marking substance, this nose being fastened removably by 
engagement to the front solid part of the tube, this nose being 
sufficiently resistant to withstand the shot, but being destructible on 
impact. 
According to the invention, the solid front part of the tube is produced in 
one piece with this tube, the diameter of this part being substantially 
equal to or slightly larger than that of the rest of the tube, the nose 
engaged on this solid front part has an inner annular shoulder bearing on 
the front surface of the solid part of the tube, and the front end of the 
nose has a plane surface i.e. is flat, this nose being shaped so that its 
wall can break under its impact on the ground. 
Thus, after impact, it is possible to remove the destroyed nose from the 
tube easily, so that the latter can be recovered. A new nose can be 
mounted on the tube so recovered, in order to obtain a training grenade 
ready for use. 
The training grenade according to the invention is thus inexpensive, since 
the most costly part, that is to say the tube, can be recovered after each 
shot. 
The front solid part of the tube gives the latter a high mechanical 
resistance which allows it to absorb the shocks on impact. Moreover, this 
front solid part of the tube is capable of trapping a real bullet fired 
inadvertently. This solid part thereby guarantees the soldiers in training 
a high degree of safety. 
Furthermore, during impact, the front of the solid part of the tube does 
not risk being damaged as a result of the inner annular shoulder of the 
nose which protects it. 
On the other hand, because the front of the nose has a plane surface, 
during the impact this will transmit to the nose an axial compressive 
force which will bring about its destruction, even if the angle of 
incidence is very low and if the ground is very loose. 
According to an advantageous version of the invention, the nose has an 
outer wall possessing thinned zones. 
These thinned zones embrittle the wall of the nose, so that the latter can 
burst easily on impact, even on loose ground. By means of these 
embrittling zones, the nose is destroyed in such a way that the tube can 
easily be recovered. 
According to a preferred version of the invention, said thinned zones 
consist of grooves made on the surface of the wall of the nose. 
Preferably, said grooves extend in the longitudinal direction of the nose. 
According to a preferred embodiment of the invention, the nose has a rear 
connector which engages on the solid part of the tube. This engagement 
makes it possible both to remove the destroyed nose so as to recover the 
tube and to reinstall a new nose on the latter. 
The nose can be produced in one piece by molding from a breakable plastic, 
such as polystyrene. 
Other particular features and advantages of the invention will also emerge 
from the description which follows.

In the embodiment of FIG. 1, the training grenade intended to be fired by 
means of a rifle comprises a metal tube 1 equipped with a rear stabilizing 
tail unit 2 and with a front solid part 3 which closes off said tube. This 
solid front part carries a hollow nose 4 containing a marking substance 5. 
According to the invention, the nose 4 is fastened removably to the front 
solid part 3 of the tube 1, this nose 4 being sufficiently resistant to 
withstand the shot, but being destructible on impact. 
The tube 1 has, for example, a total length equal to 235 mm and a diameter 
equal to 33 mm. 
FIG. 3 shows that the nose 4 has a wall possessing thinned zones 6 
consisting of grooves made on the inner surface of the wall of the nose 4 
and in the longitudinal direction of the latter. In the region of these 
grooves 6, the number of which is equal to 6 in the example shown, the 
thickness of the wall of the nose 4 is reduced substantially by half. 
Furthermore, FIG. 4 shows that the cross-section of the grooves 6 is in the 
form of an arc of a circle, the radius of curvature of which can be of the 
order of 4 mm. 
FIG. 5 shows, on the other hand, that the depth of the grooves 6 increases 
progressively from the rear towards the front of the nose 4 and stops at 
some distance from the front end 7 of the nose. 
In the example illustrated in FIGS. 1 and 3, the nose 4 has a rear 
connector 8 which engages on the solid part 3 of the tube 1. 
The thickness of the wall of this rear connector 8 is larger than that of 
the wall of the front part 4 of the nose. 
To make it easier particularly to engage the connector 8 of the nose 4 onto 
the solid front part 3 of the tube, the inner surface 8a of this connector 
has a series of ribs 8b parallel to the axis of the nose 4. These ribs 8b 
have a height of the order of a few tenths of a millimeter. These ribs 8b 
make it possible to center the nose 4 exactly relative to the tube 1 and 
provide air passages which prevent a compression of air during the 
engagement of the connector 8 onto the tube 1. 
Moreover, the front part 4 of the nose has a slightly frustoconical shape. 
The thickness of the wall of the latter decreases progressively between 
the large base and the plane small base corresponding to the end 7 of the 
nose of said frustoconical part. This plane small base forms a sharp edge 
with the lateral wall of the nose. 
In the example illustrated, the nose 4, including the rear connector 8, is 
molded in one piece from relatively breakable plastic, such as 
polystyrene. 
The inner surface 8a (see FIG. 3) of the rear connector 8 of the nose 4 
intended to be engaged on the solid part 3 of the tube 1 possesses, at its 
end adjacent to the actual nose, an annular shoulder 9, on which bears a 
plug, removable or not, or a closing plate 10 (see FIG. 1). 
This plug or plate 10 is produced from plastic, flexible or not, and bears 
on the shoulder 9 of the connector 8. It is engaged, adhesively bonded or 
welded onto this shoulder 9, as appropriate. 
The tube 1 is produced in one piece from metal or alloy, such as aluminum 
or another shock-resistant light alloy. It is produced in such a way that 
it is capable of trapping a bullet fired in error and of swelling the 
solid part 3 sufficiently to alert the firing officer of this error in a 
visible and unconcealable way. Moreover, the tube is protected by a 
colored surface treatment which cracks under the action of the 
abovementioned swelling, thus producing a highly visible ring. 
As can be seen in FIG. 1, the rear tail unit 2 of the tube 1 comprises a 
bush 14 carrying fins 15. This bush 14 is mounted in an annular recess 16 
formed at the rear of the tube 1 and retaining the tail unit 2 axially. 
This tail unit 2 is advantageously molded in one piece from plastic. 
Furthermore, FIG. 1 shows that the bottom 17 of the tube 1 has an axial 
cavity 18 of a size matched to the end of a bullet. This cavity 18 
possesses, at its entrance, an outwardly widened conical surface which is 
extended forwards by a cylindrical blind hole of a diameter equal to 2 mm. 
This cavity 18 serves for trapping the bullet of a live cartridge fired in 
error instead of a blank propellant cartridge. 
The nose 4 of the training grenade according to the invention can, as an 
example, have the following characteristics: 
type of material:polystyrene 
length:140 mm 
inside diameter of the connector 8:33 mm 
thickness of the wall of the nose:3 mm maximum, 1.5 mm minimum 
depth of the grooves 6:0.75 mm 
length of the grooves 6:60 mm 
The training grenade just described has ballistic characteristics identical 
to those of a live grenade. 
Despite the relative brittleness of the nose 4, the latter withstands the 
high acceleration which it experiences during firing. 
During this acceleration, the forces are essentially absorbed by the inner 
shoulder 9 of the connector 8, on which the rim 11 of the plug or late 10 
and the front end 3A of the solid part 3 of the tube come to bear. This 
shoulder 9 associated with a wall of relatively large thickness of the 
connector 8 allows the nose 4 to withstand the shock and also protects the 
solid part 3 in the event of the impact on a very hard solid target. 
On impact of the grenade even on loose ground, the nose 4 bursts and the 
marking powder 5 spreads over the ground. 
This bursting of the nose 4 is the result of the choice of the material of 
which it is made, the thickness of its wall, the presence of the 
embrittling zones 6 and the form and arrangement of these. 
After the impact of the grenade, the tube 1, which is the most costly part, 
can be recovered in order to reconstruct a grenade ready for use. For this 
purpose, it is sufficient to remove the part of the nose 4 remaining in 
place on the tube, namely the connector 8. It is easier to remove the 
latter because the inner ribs 8b reduce the frictional surface with the 
end of the tube. 
This operation can be carried out manually, without a tool, on the firing 
range itself. 
Likewise, the reinstallation of a new nose on the tube can be carried out 
manually without any tool. 
Of course, the invention is not limited to the exemplary embodiment just 
described, and many modifications can be made to the latter, without 
departing from the scope of the invention. 
Thus, the form and arrangement of the embrittling zones 6 on the nose 4 can 
be modified. 
Likewise, the fastening of the nose 4 on the end of the tube by engagement 
can be replaced by other means. 
Thus, the connector 8 of the nose could have an internal thread capable of 
being screwed manually onto an external thread at the end of the tube.