TRACER PROJECTILE SEALING AND IGNITION ENHANCEMENT

Abstract

A tracer projectile used in a tracer round for a firearm, the tracer projectile including a body having a forwardly directed tip, a rearwardly directed trailing end, and a cavity formed in the trailing end of the body with a rearwardly directed opening. A tracer composition is contained in the cavity. An igniter sealant overlies the tracer composition, closing and sealing the rearwardly directed opening of the cavity. The igniter sealant is a hardened layer protecting the underlying tracer composition, sealing the cavity from moisture ingress, and is flammable to ignite the underlying tracer composition.

Description

FILED OF THE INVENTION

This invention relates to Ammunition and more specifically to tracer projectiles.

BACKGROUND OF THE INVENTION

After the advent of automatic weapon technology there emerged a need to be able to guide the stream of projectiles at night or under adverse conditions where conventional sighting methods were ineffective. Prior to and during World War 1 major military powers developed projectiles which included brightly burning chemical compounds that created a “trace” or streak of light that could be used in aiming.

Typically these “tracing projectiles” are interspersed with standard bullets, armor piercing variety or other types in a proportion of one to five per each five rounds depending on operational requirements. Due to the rapid firing rate of the automatic weapon and the comparatively slow response time of the human eye, the traces produced appear to be a continuous “beam of light” to the operator.

To produce a tracing round, a hollow base projectile is packed with a pyrotechnic composition or base charge designed to burn brightly in the visible or non-visible spectra. The base charge can be directly packed in the hollow base, a previously formed pyrotechnic compound pellet can be inserted into the cavity, or a previously similarly packed cup can be inserted into the cavity. During packing a conical shape of the surface of the chemical compound is finally impressed, to provide a larger surface area for ignition. An igniter charge is commonly layered over the base charge to facilitate ignition.

The base charge as well as any igniter charges are quite hydrophilic and are often sealed against moisture and protected with varying degrees of success. Conventionally, either no sealant is applied, varnish is applied to the surface as a sealant and moisture barrier, or copper discs are pressed into the base to protect the compound during storage prior to loading.

Unfortunately, since the invention of the tracing projectile more than one hundred years ago there has been little progress beyond improved chemical compositions for the main pyrotechnic charge. At the US Army Lake City Army Ammunition Plant (LCAAP) facility, machinery produced for WW-1 preparation of 0.30 caliber tracing projectiles and originally designed to be driven by overhead shafts and leather belts are still used today to make 7.62×51 mm M62 Tracers.

In addition, the current designs of tracing projectiles specify a thin Copper disc “seal” be placed over the base of the bullet covering the chemical compound which neither fulfills the function of preventing moisture intrusion nor enhances ignition of the compound due to its inflammable nature. Copper tracing projectile discs are apparently only present to protect the compound from damage from bullet tips when stored in bulk containers prior to loading into cartridges. Moisture penetration is confirmed by the fact that LCAAP projectiles are stored in desiccant containers to preserve their function and some current US specifications call for 70-yard minimum ignition which may be the best that can be achieved with an inflammable metal disc in the way of the flame from combustion within the cartridge.

An additional problem with conventional tracer projectiles is that the combustion of material from the large cavity quickly changes the ballistics of the projectile causing it to deviate from the path of the conventional projectiles fired with it. This result is exacerbated by the increased cavity needed to provide space for the conical depression to increase surface area.

It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.

An object of the present invention is to provide a sealed tracer projectile that protects the tracing compound, enhances ignition and provides a moisture resistant seal as well.

SUMMARY OF THE INVENTION

Briefly to achieve the desired objects and advantages of the instant invention in accordance with a preferred embodiment provided is a tracer projectile used in a tracer round for a firearm. The tracer projectile includes a body having a forwardly directed tip and a rearwardly directed trailing end. A cavity is formed in the trailing end of the body with a rearwardly directed opening. A tracer composition is contained in the cavity, and an igniter sealant overlies the tracer composition, closing and sealing the rearwardly directed opening of the cavity. The igniter sealant is a hardened layer protecting the underlying tracer composition, sealing the cavity from moisture ingress, and is flammable to ignite the underlying tracer composition.

Also provided is a method of fabricating a tracer projectile including the steps of providing a projectile body having a forward end, a trailing end, and a cavity in the trailing end with a rearwardly directed opening. A tracing composition is placed in the cavity, the tracing composition having a rearwardly facing surface. A fluid igniter sealant including an epoxy resin, a mercaptan hardener, and a flammable additive is mixed. The fluid igniter sealant is deposited over the surface of the tracing composition, closing the rearwardly directed opening. A hardened igniter sealant is formed by curing the fluid igniter sealant The hardened igniter sealant overlying the tracer composition, closing and sealing the rearwardly directed opening of the cavity, the hardened igniter sealant protecting the underlying tracer composition, sealing the cavity from moisture ingress, and being flammable to ignite the underlying tracer composition.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific objects and advantages of the invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof, taken in conjunction with the drawings in which:

FIG. 1 is a sectional side view of a conventional NATO tracer projectile;

FIG. 2 is a sectional side view of a tracer projectile according to the present invention;

FIG. 3 is a sectional side view of another embodiment of a tracer projectile according to the present invention;

FIG. 4 is a simplified flow chart of a method of fabricating a tracer projectile according to the present invention.

DETAILED DESCRIPTION

Turning now to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is directed to FIG. 1 which illustrates an example of a conventional tracer projectile generally designated 10. Projectile 10 includes a jacket 12 and a point filler 14 filling a forward end thereof. A cavity 15 is define by jacket 12 extending rearwardly beyond a base 16 of point filler 14 to an open rear end 17. A tracer composition 18 (base charge) is packed into cavity 15 against base 16. To enhance ignition, a conical depression 20 is formed in tracer composition 18 to increase the surface area which is available for ignition. Conical depression 20 is coated with an ignition layer 22 and potentially, as illustrated, a sub-ignition layer 24 between the ignition layer and the tracer composition 18. Conical depression 20 is maintained in these layers to continue to provide a greater surface area to facilitate ignition. Open rear end 17 of jacket 12 is closed by insertion of a closure cup or disk 25 which is crimped in place by rear end 17 being deformed inwardly. While somewhat effective in protecting and preventing damage to the underlying charges, closure cup or disk 25 is suspect as a seal when moisture is present. Since tracer composition 18, ignition layer 22 and sub-ignition layer 24 are hydrophilic, the presence of moisture and an insufficient seal create defects in projectile 10 and possibly a completely unusable projectile 10.

An additional problem with conventional trace projectile 10 is that the combustion of material from the large cavity quickly changes the ballistics of the projectile causing it to deviate from the path of the conventional projectiles fired with it. This result is exacerbated by the increased cavity needed to provide space for conical depression 20.

Turning now to FIG. 2, an example of a tracer projectile 30, according to the present invention, is illustrated. Projectile 30 includes a body 31 having a jacket 32 and a point filler 34 filling a forward end thereof. A cavity 35 is define by jacket 32 and extends rearwardly from a base 36 of point filler 14 to an open trailing end 37 of jacket 32. A tracer composition 38 (base charge) is packed into cavity 35 against base 36. In tracer projectile 30 of the present embodiment, the tracer composition 38 has a flat rearward surface 40. One of ordinary skill in the art will understand that tracer composition 38 can be any one of a variety of well known tracer compositions. A layer of igniter sealant 42 is deposited over rearward surface 40 of tracer composition 38. Igniter sealant 42 adheres to jacket 32 and completely closes and seals open trailing end 37 without the need for a closure cup or crimping. Additionally, igniter sealant 42 acts as an igniter for tracer composition 38, a moisture barrier and since it is a hardened material, protection from impacts.

It will be understood that while tracer projectile 30 includes a jacket 32, an unjacketed projectile can also be employed with cavity 35 formed in the base thereof. Referring now to FIG. 3, a tracer projectile 130, according to the present invention, is illustrated. Projectile 130 includes a body 131 having a forward tip 133 and a rearwardly directed trailing end 134. A cavity 135 is formed in and defined by trailing end 134 of body 131 with a rearwardly directed opening 137. A tracer composition 138 (base charge) is packed into cavity 135 with the level of tracer composition slightly forward of trailing end 134 within cavity 135. In tracer projectile 130 of this embodiment, tracer composition 138 has a flat rearward surface 140. One of ordinary skill in the art will understand that tracer composition 138 can be any one of a variety of well know tracer compositions. A layer of igniter sealant 142 is deposited over rearward surface 140 of tracer composition 138. The conical area that would be in the conventional tracer projectile is not present and is now filled for an increase of volume of tracer composition 138 of 15% or more. Igniter sealant 142 is an adhesive sealant, such as a two part epoxy, a one part epoxy which is generally light cured, a urethane adhesives, acrylic adhesives and the like, with flammable additives. The adhesive sealant is used in igniter sealant 142 with the addition of flammable additives. Igniter sealant 142 is deposited to completely fill the remaining, now flat space at trailing end 134 of body 131, which then cures to form a hardened seal across the entire surface. Trailing end 134 of body 131 is protected from damage prior to and after assembly in a cartridge. In use, the flame of gunpowder combustion causes flammable igniter sealant 142 to uniformly light the surface of underlying tracing composition 138 while also providing protection for tracing composition 138 before loading and against the initial thermal and pressure spike that expels projectile 130. As a result, more uniform ignition of tracers is obtained, the distance the visible trace occurs may be manipulated, the balance of the bullet due to weight distribution changes through tracing compound combustion is able to be altered for longer distances matching the trajectories of standard projectile and the total volume of composition 138 is increased for extended range before burnout.

In the previous embodiments, igniter sealant 42, 142 can contain formulations which delay the ignition of the tracer while still assuring initiation. Upon firing, the projectile may appear dimly visible or visible only within the infrared spectrum until the surface combustion of the igniter sealant 42, 142 penetrates to underlying tracing composition 38, 138. At that time the tracer may be seen for a longer range by virtue of a delay in the ordinary ignition range of the projectile. Further extension of visible burning range is increased with the increased internal volume of tracing composition 38, 138 due to the elimination of the conical depression. Similar changes in the distance which trajectory disturbing imbalances accrue, enhancing accuracy and trajectory match also improve. In this manner, a reliably sealed and igniting tracer projectile can be produced that rather than burning from, for example, 70 yards to 2,950 yards with only a 660 yard match to the standard projectiles, the tracer may burn from an agreed upon ignition range, then last longer than the 2,880 yards above and loses balance more slowly due to more volume of compound at the base of the projectile. This enables an estimated distance of trajectory match to the other four rounds it is supposed to be guiding to the target to increase substantially.

In the previous embodiments, ignition sealant 42, 142 is an epoxy resin with hardener that will seal and protect the underlying tracer composition. The epoxy with hardener will cure very hard for protection and prevent moisture ingress. Flammable additives are added to both the resin and the hardener and can be adjusted for a quick hot burn or a slower cooler burn as desired. The flammable epoxy resin includes at least 60% by weight epoxy resin and 40% or less by weight flammable additive. The hardener is at least 60% hardener by weight and 40% or less by weight, flammable additive. The preferred hardener is a composition of Mercaptan Terminated Polymer (60-100% by weight), Substituted Aminophenol (7-13% by weight) and Carbon Black (1-5% by weight). The epoxy resin is preferably a Bisphenol A Epoxy Resin. To these compositions are added a flammable additive. The flammable additive can include one or more different agents including a carbonaceous agent and a metallic agent. The carbonaceous agent includes but is not limited to carbon black, nitrocellulose, nitrosamines, and hydrocarbons. Metallic agents include but are not limited to powdered metal such as powdered aluminum and the like.

Turning now to FIG. 4, a method of fabricating a tracer projectile is illustrated. Step 210 includes providing a projectile body having a forward end, a trailing end and a cavity in the trailing end with a rearwardly directed opening. Step 212 includes placing a tracing composition in the cavity. The tracing composition is formed to have a rearwardly facing surface. Step 214 is mixing a fluid igniter sealant. The fluid igniter sealant includes an adhesive sealant such as an epoxy resin, a mercaptan hardener, and a flammable additive. However it will be understood that other adhesive sealants such urethane adhesives, acrylic adhesives, and the like, can be used with flammable additives to provide the fluid igniter sealant. As described previously. Step 216 is depositing the fluid igniter sealant over the surface of the tracing composition and closing the rearwardly directed opening. Step 218 is forming a hardened igniter sealant by curing the fluid igniter sealant. The hardened igniter sealant overlies the tracer composition, closing and sealing the rearwardly directed opening of the cavity. The hardened igniter sealant forms a layer protecting the underlying tracer composition, sealing the cavity from moisture ingress, and being flammable to ignite the underlying tracer composition.

The present invention is described above with reference to illustrative embodiments. Those skilled in the art will recognize that changes and modifications may be made in the described embodiments without departing from the nature and scope of the present invention. Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof.

Claims

1. A tracer projectile used in a tracer round for a firearm, the tracer projectile comprising: a body having a forwardly directed tip and a rearwardly directed trailing end;a cavity formed in the trailing end of the body with a rearwardly directed opening;a tracer composition contained in the cavity; andan igniter sealant overlying the tracer composition, closing and sealing the rearwardly directed opening of the cavity, the igniter sealant is a hardened layer protecting the underlying tracer composition, sealing the cavity from moisture ingress, and is flammable to ignite the underlying tracer composition.

2. The projectile as claimed in claim 1 wherein the igniter sealant comprises: an adhesive sealant; anda flammable additive.

3. The projectile as claimed in claim 2 wherein the adhesive sealant includes one of an epoxy, a urethane adhesive, and an acrylic adhesive.

4. The projectile as claimed in claim 1 wherein the igniter sealant comprises: an epoxy resin;a mercaptan hardener; anda flammable additive.

5. The projectile of claims 2 wherein the flammable additive includes at least one of a carbonaceous agent and a metallic agent.

6. The projectile of claims 5 wherein carbonaceous agent includes at least one of carbon black, nitrocellulose, nitrosamines, and hydrocarbons.

7. The projectile of claim 1 wherein the igniter sealant comprises: a first part having at least 60% by weight epoxy resin and 40% or less by weight flammable additive; anda second part having at least 60% hardener by weight and 40% or less flammable additive by weight.

8. The projectile as claimed in claim 1 wherein the body comprises a jacket having a forward end corresponding to the forward tip of the body and a rearward end corresponding to the trailing end of the body, a point filler filling the forward end of the jacket, and the cavity defined by the rearward end of the jacket and extending rearwardly from a base of the point filler to the rearwardly directed opening.

9. A tracer projectile used in a tracer round for a firearm, the tracer projectile comprising: a body having a forwardly directed tip and a rearwardly directed trailing end;a cavity formed in the trailing end of the body with a rearwardly directed opening;a tracer composition contained in the cavity having a flat rearwardly directed surface; andan igniter sealant including an adhesive sealant, and a flammable additive, overlying the tracer composition, closing and sealing the rearwardly directed opening of the cavity, the igniter sealant is a hardened layer protecting the underlying tracer composition, sealing the cavity from moisture ingress, and is flammable to ignite the underlying tracer composition.

10. The projectile as claimed in claim 9 wherein the body comprises a jacket having a forward end corresponding to the forward tip of the body and a rearward end corresponding to the trailing end of the body, a point filler filling the forward end of the jacket, and the cavity defined by the rearward end of the jacket and extending rearwardly from a base of the point filler to the rearwardly directed opening.

11. The projectile of claims 9 wherein the flammable additive includes at least one of a carbonaceous agent and a metallic agent.

12. The projectile of claims 11 wherein carbonaceous agent includes at least one of carbon black, nitrocellulose, nitrosamines, and hydrocarbons.

13. The projectile of claim 9 wherein the igniter sealant comprises: a first part having at least 60% by weight epoxy resin and 40% or less by weight flammable additive; andthe second part having at least 60% hardener by weight and 40% or less flammable additive by weight.

14. The projectile as claimed in claim 9 wherein the adhesive sealant includes one of an epoxy, a urethane adhesive, and an acrylic adhesive.

15. A method of fabricating a tracer projectile comprising the steps of: providing a projectile body having a forward end and a trailing end;providing a cavity in the trailing end with a rearwardly directed opening;placing a tracing composition in the cavity, the tracing composition having a rearwardly facing surface;mixing a fluid igniter sealant including an adhesive sealant, and a flammable additive;depositing the fluid igniter sealant over the surface of the tracing composition and closing the rearwardly directed opening; andforming a hardened igniter sealant by curing the fluid igniter sealant, the hardened igniter sealant overlying the tracer composition, closing and sealing the rearwardly directed opening of the cavity, the hardened igniter sealant protecting the underlying tracer composition, sealing the cavity from moisture ingress, and being flammable to ignite the underlying tracer composition.

16. The method of claims 15 wherein the flammable additive includes at least one of a carbonaceous agent and a metallic agent.

17. The method of claims 16 wherein carbonaceous agent includes at least one of carbon black, nitrocellulose, nitrosamines, and hydrocarbons.

18. The method of claim 15 wherein the fluid igniter sealant comprises: a first part having at least 60% by weight epoxy resin and 40% or less by weight flammable additive; anda second part having at least 60% hardener by weight and 40% or less flammable additive by weight.