.408 Cheyenne Tactical -- A Novel 2,000-Meter Tactical Cartridge

- Part II -

 By John D. Taylor

            Colonel Michael D. Wyly proposed that as we enter the 21st Century the Mental Agility Theory would place the Technology Superiority Theory under a greater challenge than it experienced in the past (1).  The core of the latter is founded upon high-performance aircraft, smart bombs, long-range missiles, and electronic sensors, secure communications and computerized information technology -- all to be utilized against a less sophisticated foe.

            On the other hand, logic fundamental to the Mental Agility Theory proposes that technology central to the Technology Superiority Theory can be circumvented by a determined foe whose numbers are so dispersed that as targets, they are too numerous to be neutralized by the Technology Superiority Theory.  The U. S. experience in Vietnam serves as a supportive example.

            In order to counteract such a dispersed force, a defender would be required to field a body of equally or more agile, well-trained individuals.  To some extent, in response to terrorist activities, this description can be extended from the military to federal, state and local law enforcement levels.

            The Technology Superiority Theory will continue to prevail for the foreseeable future.  However because we are influenced by our military past, particularly Vietnam, the transition

from the Technology Superiority Theory to the Mental Agility Theory has accelerated.  This was exemplified during Desert Storm where small groups of dedicated U.S. Marines were deployed behind enemy lines before the initiation of the ground attack, 39 hours later.  Their purpose was several-fold, including instilling confusion among the enemy.  They were successful, and in the end, tactics, not technology, prevailed.

            The Mental Agility Theory proposes that an enemy force with some sophisticated technology, but behaving in an untraditional manner, would be able to dismantle a nation's technology.  As preventative measures, Colonel Wyly predicts that the traditional solider of our past -- the one with agility, toughness, field training etc., will rise in importance during the next century as well as his primary weapon, his rifle!

Even though some evolutionary dead-ends have been encountered -- best exemplified by the Flechette firing rifles (2), the evolution of rifle and cartridge since the Vietnam conflict has not been one of new advancement in design; but instead, one of improvements of existing designs.  Turn-bolts as well as semi- or select-auto designs of yesterday remain with us today now with major improvements in accuracy, ergonomics and reliability.  With the exception of the .338 Lapua Magnum cartridge, calibers of today are the same as those used during the Vietnam era.  However today their components have improved greatly which have provided the shooter with greater precision and distance.

            Due to the emergence of tactics proposed by the Mental Agility Theory in relation to the potential of increased terrorist activities, many in military and federal law enforcement leadership positions believe that in the future, "combat" may become limited to small or restricted areas -- in

some cases in urban environments. 

Battlefields of tomorrow will be desolate compared to those of the past.  This is evidenced as the number of soldiers per unit area has dropped from a high of that found at Waterloo to conflicts of today.  It appears reasonable that the numbers per unit area will continue to drop resulting in fewer targets.  Projectile saturation of a given per unit area will yield minor benefits.  Instead, precision projectile placement will become paramount -- in some cases, precision projectile placement at long distances.  As a result, new weapon systems and their cartridges are being developed to meet these needs.

            Previously, I brought to your attention a new long-range cartridge that my partner -- William (a.k.a. Willi) Wordman and I were in the early stages of designing (3).  The cartridge is called the .408 Cheyenne Tactical or .408 CheyTac (Figure 1).  This article describes our progress since my previous article. 

We believe that the .408 CheyTac will become the sniper cartridge of choice for targets, especially hard targets between 1000 and 2000 meters.  In addition, we believe that it will fill an ongoing need for a cartridge that will be a major improvement over the 7.62mm NATO currently being used in the General Purpose Machine Gun (GPMG). 

For sniping, we envision the .408 CheyTac  projectiles penetrating light armor carriers, communication centers, grounded aircraft etc. and at the same time, limiting the collateral damage to innocent non-participants.  The time is emerging for such a sniper cartridge.

            For the GPMG, the .408 CheyTac  is ideal as an enhanced cartridge over the 7.62mm NATO used today in the GPMG.  Today a major gap exists between the 7.62mm NATO cartridge and the .50 Browning cartridge.  Should that gap be filled with a new cartridge -- intermediate between the 7.62mm NATO and the .50 Browning cartridges?  For over a score of years, some have claimed that the U.S. Army has desired such an intermediate cartridge for their GPMG.  The logic is that the 7.62mm NATO cartridge is too light, while the .50 Browning cartridge is too heavy.  An intermediate cartridge would extend the benefits of the 7.62mm NATO, while at the same time not assume the detriments of the .50 Browning; e.g., weight of cartridge, amount of space taken by the cartridge etc. 

It appears that the military's search has been more casual than serious.  Perhaps the reason is that the adoption of a new military cartridge is not common and only occurs when a genuine need exists.  Perhaps that need has yet to emerge.  At the time of its introduction, the .338 Lapua Magnum cartridge was proposed to fill this intermediate gap, first as a sniper cartridge and as an after thought, a cartridge for the GPMG. 

The parental cartridge case for the .338 Lapua Magnum is the .416 Rigby (for a review of the history, see 4, 5).  Today, the .338 Lapua Magnum cartridge is considered by some to be a true intermediate between 30 and 50 calibers, while in reality its physical and ballistic characteristics are closer to a 30 caliber than to a 40 caliber -- the 40 caliber representing the intermediate.  A true intermediate cartridge would not only be intermediate in caliber, but intermediate in cartridge size, projectile weight, kinetic energy and effective range as well.  The .338 Lapua Magnum is an excellent long distance anti-personnel cartridge for distances up to 1300 meters, but the majority of its useful kinetic energy is exhausted by 1000 meters, which makes it a less effective anti-material cartridge beyond that distance.

            Even if the military's quest to find a true intermediate cartridge has been casual, why didn't someone design one?  Development of hunting and benchrest cartridges via "wildcatting" is not that common, but a dedicated core of wildcatters searching for the right combination does exist.  The same cannot be said for a dedicated core of wildcatter searching for the right military cartridge.  There is no incentive for such a search.  As a result, either cartridge designers were uninterested in the challenge or those few wildcatters interested in a new military cartridge were unable to identify an ideal parental cartridge case to serve their needs.  With the latter, the logical approach would be to modify an existing cartridge case, which is larger than 40 caliber and neck it down to fit a 40-caliber projectile rather than designing a new cartridge case de novo. 

It is reasonable that one would take a pre-existing 50-caliber cartridge case and neck it down to 40 caliber.  For example, necking down a 50-caliber cartridge case has been achieved with the .50 Browning as well as with the .50 Browning spotter round.  The .50 Browning cartridge case probably has been necked down to most of the popular calibers including the .223.  However, I argue that necking down a .50 Browning cartridge case to a 40 caliber would not represent a true intermediate because the resulting cartridge remains a .50 Browning, which is housing a 40-caliber projectile.  It does not represent a cartridge where the cartridge case and projectile are proportionally intermediate between the 7.62mm NATO and the .50 Browning cartridges. 

For a true intermediate between the 7.62mm NATO and the .50 Browning cartridges, the cartridge case must be intermediate as well.  Approximately three years ago, I published a study on large caliber parental cartridge cases (6).  Focusing on desirable characteristics including a cartridge case without a belt, my study revealed that several cartridge cases could be considered as good candidates for the intermediate between the 7.62mm NATO and the .50 Browning cartridges.  One stood out among the others; it was the .505 Gibbs cartridge case.

Assuming the .505 Gibbs was the ideal parental cartridge case, the next step was to mate the .505 Gibbs cartridge case with a 40-caliber projectile.  Caliber sizes ranging from .400 to .436 were examined.  Existing 40-caliber projectiles such as the .416 were not considered because this novel caliber was to become associated with military usage rather than a caliber associated with big game hunting.  In the end, .408 caliber was selected -- one full caliber larger than the 7.62mm NATO (.308 Winchester) cartridge and slightly one full caliber smaller than the .50 Browning cartridge (Figure 2).

The .408 Cheyenne Tactical  Cartridge Case

The .505 Gibbs cartridge made its appearance as the .505 Rimless Magnum cartridge.  Later, it became known as the .505 Gibbs cartridge -- in part due to Ernest Hemingway's short story entitled, The Short Happy Life of Francis Macomber.  While on safari in Africa with Robert Wilson, a professional hunter and guide, Francis Macomber demonstrated cowardice in the face of a charging lion.  Wilson used what Hemingway called a .505 Gibbs cartridge and the name stuck.  In addition, the illustrious and famous African hunter, John "Pondero" Taylor (no relation) often referred to the cartridge as the .505 Gibbs.   When the Mauser action became available in

1898, a number of British gun makers designed dangerous game cartridges that could be used with it.  George Gibbs of Bristol introduced the .505 Rimless Magnum cartridge in 1913.  It was the largest of the cartridges designed for the Mauser action.

            The .505 Gibbs cartridge was designed for a maximum chamber pressure of 45,065 psi (Piezo) with most commercial loads yielding chamber pressures in the mid-30,000's psi accompanied with muzzle velocities in the low-2,000's fps.  What brand of .505 Gibbs cartridge case was available to conduct initial studies?  One manufactured by Bruce Bertram of Bertram Bullet Ltd. (Australia) was selected, but Bruce was manufacturing his cartridge case for chamber pressures associated with the original .505 Gibbs cartridge.  Would the Bertram cartridge case, in its original state be the best choice to launch a 40-caliber projectile to meet the desired goal out to 2000 meters? 

Rather than "reinventing the wheel," Willi and I examined the approach that Jim Bell (MAST Technology, Las Vegas, NE) and Boots Obermeyer (Obermeyer Barrel, Bristol, WI) utilized with another turn-of-the-century dangerous game cartridge -- the .416 Rigby, in order to sire it into the .338 Lapua Magnum cartridge.  Taking cartridge cases from the .505 Gibbs (Bertram Bullet), from the .416 Rigby (Bertram Bullet & MAST Technology) and from the .338 Lapua Magnum (Nammo Lapua Oy), Willi made longitudinal cuts that allowed morphological comparisons to be made between cartridge cases.  Jim Bell's secret was a redesign of the cartridge case web.  Part of the redesign was an increase in web thickness.  In addition, the web from Nammo Lapua Oy's .338 Lapua Magnum cartridge case was also thicker than that from Bertram Bullet's .416 Rigby cartridge case, but not as thick as that found with the MAST Technology's .416 Rigby cartridge case. 

At the time of the development of the .338 Lapua Magnum cartridge, Jim Bell had taken one of his .416 Rigby cartridge cases, strengthened the web and redesigned the case to the .338-.416 cartridge (4).  Later Nammo Lapua Oy made some additional modifications, when they started to manufacture their cartridge.

The longitudinal halves were sent to Bruce Bertram for his review and comments.  I was hoping that he would take a hint and volunteer to make his next batch of .505 Gibbs cartridge cases with a strengthened web.  He did and the next batch of Bertram's .505 Gibbs cartridge cases displayed a strengthened web, but with a step built in between the wall and the web.  Even though the wall and web were not continuous, but instead interrupted by the step, the cartridge case was clearly stronger than its predecessor and preliminary testing was ready to proceed.

During this period, I was engaged in writing two articles on the .338 Lapua Magnum cartridge (3, 4) and as a result, I spent some time with both Jim Bell and Boots Obermeyer for background information.  Based on insight from these two gentlemen, it became clear that if the cartridge's design and its subsequent manufacturing were to be accomplished correctly, a cartridge case that was especially designed for the .408 CheyTac  cartridge should be created de novo. 

Jim's son, Jay Bell (Figure 3), was beginning to take a leadership role in MAST Technology so we met with Jay and his father in order to ask for help in order to move the project forward.  Even though Jim had played a prominent role in the development of the .338 Lapua Magnum cartridge, it appeared that his son, Jay would soon become immersed in the .408

CheyTac  project.  Traditions of progress that go from one generation to the next always works for me.

            My sense is that Jay Bell is a businessman first, and a cartridge case designer second.  He quickly brought Willi and I out of the clouds to reality when he started talking about the cost of this project.  Even though 1000 cartridge cases would more than serve our needs, MAST Technology could not get geared up for a production run for less than 30,000 cases.  We asked ourselves, "Where would we store 30,000 cases?" 

A compromise that served both of our needs was found.  Jay felt that there might be a market for a cartridge case lager than the .416 Rigby, which traditionally has been a big seller with MAST Technology, and he liked everything that I said about the .505 Gibbs cartridge.  In the end, MAST Technology decided to manufacture two cartridge cases: .408 CheyTac  and .505 Gibbs.  Both cartridge cases possess strengthened webs with the wall facing the interior continuous with the web in the configuration of a descending arc into the web.  To change the configuration from the .505 Gibbs to the .408 CheyTac  cartridge case requires one additional tooling step.  At that time, we were still experimenting with the overall dimensions of our cartridge case, so the first two thousand .408 CheyTac  cartridge cases manufactured were in the .505 Gibbs configuration displaying our head stamp (Figure 4).  Because these cartridge case hybrids will require neck sizing, Willi constructed a fixture that will fire-form them to the .408 CheyTac  neck dimensions. 

Dave Manson (Dave MANSON Precision Reamers, [a.k.a. Loon Lake Precision], Grand Blanc, MI) made the first two chamber reamers.  One reamer chambered two barrels used in our

tests, while the other was sent to Lloyd DeSantis (RND Manufacturing, Longmont, CO).  It would be used to chamber a new semi-auto gas rifle in the .408 CheyTac  caliber once Lloyd had completed the RND 2000 Tactical prototype chambered in the .338 Lapua Magnum cartridge.  However before he could start the project, the infamous and sly Pete Forras  -- best known for shenanigans appearing on the pages of Precision Shooting magazine, put a spell on Lloyd resulting in the chamber reamer being enticed away from him.  It's now making stops at every rifle builder located in the Pacific Northwest.  Recently a Canadian rifle maker telephoned to thank me for the reamer and to inform me that his just completed big game rifle will shoot the ".416 Cheyenne" cartridge.  His cartridge will use commercial .416 projectiles.  This is probably the first of many wildcats to come.    

The .408 Cheyenne Tactical  Projectile       

            It was clear during the early stages of the cartridge's design that the projectiles would be solids and would be manufactured via a CNC lathe.  A starting design point was required and that turned out to be the 300gr .338 Sierra Match King projectile.  Proportionally, enlarging the 338 caliber to a 408 caliber was easy.  This led to the development of two projectile designs: one with a driving band and one without.  The projectile with the driving band turned out to be 12grs lighter than the one without the driving band (Table I). 

Projectiles with two boat-tail angles; i.e., 5 and 7 degrees are currently under study.  Research conducted by NASA and others revealed that boat-tail angles greater than seven degrees increase tail drag.  As a rule of thumb, 6.5 degrees appears to be ideal for projectiles subjected to supersonic velocities (7, 8).  The ogive and meplat diameter in relation to the .408 caliber were

determined using the projections first outlined by Krasnov (9).  The bronze alloy utilized for the first two projectiles was C93200 with 7% lead and a Brinell hardness scale of 72.  Another alloy with 30% lead content is in early stages of investigation (Table I).

            The projectile's overall length of 2.00 inches is not envisioned to change; however, it is possible that it might become slightly shorter in case instability is detected during flight during upcoming tests.  At this time, projectiles have only been taken out to 1000 meters (1194 yards), but not farther.  Performance was outstanding and no evidence of instability was found.  As yet, projectile yaw and pitch data beyond 1000 meters has not been collected.

Because the research has not reached the point to where the ballistic coefficient (BC) of the projectiles under various conditions can be measured, "McDrag" modeling (11) is being utilized that provides a wide range of possible BCs.  For design purposes, a conservative BC of 0.88 is being utilized but the actual BC is probably closer to 0.9

            Table II provides specifications and properties for the cartridge case and three projectiles currently under study.  At this time, we are happy with the cartridge case specifications.  Future research dealing with full automatic fire in the GPMG may result in increasing the body taper another 0.5 degree but at this time, the taper of 0.5 degree appears to be adequate.

Development of Prototype Rifle - Prometheus

            For cartridge development, a shooting platform was required.  Some cartridge developers approach the task by putting together a "bare bones" rifle without any consideration to its overall

appearance and details in the machining.  These platforms are usually referred to as "shop mules."  A shop mule was constructed; but Willi is a perfectionist so he constructed an elegant shop mule -- he called Prometheus.  In its finished state, it represents a great custom rifle that will hold its own to the eye of any critical rifle maker (Figure 5).   

The heart of any rifle is its barreled action.  Because the rifle was intended for tactical shooting, a light turn bolt repeater rifle made from titanium was the goal.  Willi and Gordon Robertson (5 Star GR, Trinidad, CO) completed the design.  However before a prototype was constructed, Willi discovered a rifle action manufactured by Tony Gilkes, which was impressive, particularly the 45-degree angle on the locking lugs (Figure 6).  Several conversations with Tony convinced us, that his aluminum receiver would be ideal.  Rather than constructing the newly designed action, our full energy was now devoted to the development of the cartridge.  We did not abandon the newly designed action; the design is now be digitized for CNC construction with the assistance of the tactical stock maker, Goran Stanojevic (A & N Enterprises, Scarborough, Ontario, Canada) and will be constructed at a later date.  

Gilkes aluminum receiver is reinforced with steel inserts in those areas of stress.  The two problems' encountered with the receiver were that it was a single shot and the bedding block was too short to satisfy our needs.  Willi quickly magazine-ported the receiver and constructed a magazine.  In addition, he made a new V-shaped bedding block.

            We turned to John Krieger (Krieger Barrels, Inc., Germantown, WI) for two fluted barrels.  Since the caliber is new, Krieger performed a few tricks to achieve the .408 groove diameter and .400 bore diameter.  Subsequently, the barreled action was sent to McMillan

Fiberglass Stocks (Phoenix, AZ) to be stocked.  At the time, John Davis was with McMillan handling custom stocks, and he adapted the Big Mac stock to attach to Willi's V-shape bedding block, which was accomplished via four bolts that terminated with two bolts on each side of the forearm.  The rifle was braked by Bruce McArthur's PGRS brake (Flint & Frizzen, Clark, MI) and was scoped by a Leupold Vari-X 6.5-20x50mm power boosted to 20-50 (Premier Reticle Ltd., Winchester, VA).

            Even though the completed shop mule weighed 24 pounds and was barrel-heavy, it was ready for cartridge load development.  During the period that the loads were being developed, ways in which the weight of the rifle could be reduced were explored.  One approach would be to send the second barrel to Christenson's Arms to be turned and graphite-wrapped. 

On a return trip from California, I stopped by Christensen's Arms in St. George, Utah (Figure 7) and spent a pleasant day with Evan A. Mitchell (Operations Manager & Master Gunsmith) and John Mogle (Sales).  During the visit, they convinced me that graphite wrapping would not only improve the accuracy of the second Krieger barrel, but would also reduce heat accumulation, which in turn, would maintain a constant bore diameter.  As a bonus, the barrel would lose weight as a result of the process.  When the Krieger barrel returned from Christensen's Arms and replaced the fluted barrel, the rifle became 5.5 pounds lighter and was no longer barrel-heavy. 

Critical tests, contrasting the accuracy between the Krieger fluted and the Krieger fluted barrel turned down and graphite coated by Christensen Arms have yet to be scheduled.  However, the first 3-shot group at 100 yards using our cartridge cases manufactured by MAST Technology

and our projectiles yielded a 0.323 MOA at 100 yards that has yet to be achieved with the fluted barrel.  As a side note, we have been able to obtain 0.6 MOA with Bertram Bass cartridge cases at 1000 meters, which at the time was not being shot for groups.

Initial Cartridge Load Development.

Note: Because studies were performed with cartridge cases from Bertram Bullet Ltd. and not MAST Technology, ballistic characteristics and powder loads should be viewed as tentative and not as absolute.  Ballistic characteristics and powder loads discussed here represent comparative values only; i.e., contrasting one type of powder with another. Therefore, all ballistic data presented here must be considered tentative until studies have been repeated and refined with MAST Technology cartridge cases.  That data will be presented in a subsequent article.

            Cartridge load development was accomplished with the assistance of Dr. Steve Faber (Fabrique Scientific, Batavia, IL).  During load development, a strain gauge was glued to the barrel over the chamber region (Figure 8).  This was connected to the Peak Strain Meter, developed by Dr. Faber (10, 11).  The Peak Strain Meter is a small plastic cased meter powered by a single 9V battery providing an LCD numerical readout of the strain reading.  The gauge is a thin plastic film with a resistive circuit pattern about " by " that measures to the nearest millionth of an inch, the elongation in the rifle's chamber when the cartridge is fired.  The strain is proportional to the chamber pressures, which determine relative pressure or absolute pressure when calculated using a pressure vessel formula.

The following powders were examined: Ram Shot's Big Boy, Reloader 25, VihtaVuori N165, N170, N560 and 20N29.  Figure 9 demonstrates a comparison between five different powders propelling full body projectiles in the Christensen graphite barrel.  Note that the VV N170, N560 and the Reloader 25 have similar rise times.  In addition the VV N560 and Reloader 25 have similar muzzle pressures that are greater than do those of the other powders.  The VV N560 is represented here as a lower charge than the Reloader 25, but it keeps pace with the Reloader 25 due to its double base composition.  Ram Shot Big Boy is a ball powder and demonstrates a higher rise time than the other powders. It demonstrates an advantage of a rounded peak (i.e., longer sustained pressure) over the other powders, but with the higher powder weights -- necessary for desired muzzle velocity as shown in this figure, it loses this advantage.

The studies with the Bertram Bullet cartridge cases did reveal one tentative conclusion.  The slow burning large caliber magnum powders appeared to burn slightly too fast for the .408 CheyTac  cartridge, while the powders typically used for .50 Browning cartridge appeared to burn slow.  In other words, chamber pressures recorded, using the typical large magnum powders were in the low 70,000s psi (MVs from 2750 to 2850 fps) even though the cartridge cases were not close to being filled.  On the other hand, chamber pressures using VV 20N29 were in the high 30,000s to the low 40,000s psi (MVs from 2350 to 2450 fps) with the cartridge case filled to capacity. 

Similar results appear to be the case with the MAST cartridge cases.  Jay shipped eight cartridge cases for our approval before the order of 2000 cartridge cases was finalized.  With our best maximum loads (using several different powders, but not VV 20N29), chamber pressures

were in the low 70,000s psi with muzzle velocities in the low 2800s fps -- an additional 17 grains of powder can be added before reaching a compact load.

The relative burning rates of several VihtaVuori powders (Nammo Lapua Oy, Finland) used the studies ranged from N165 = 47; N170 = 41; and 20N29 = 36 (13).  For the future our focus will be centered between burning rates of 41 and 36.  We shall first examine the VV 24N41, which has a burning rate of 38.  This may be an ideal powder for the .408 CheyTac.     

            For comparative purposes only, a summary of the results using cartridges made from Bertram Bullet cartridge cases are presented.  They reveal chamber pressures recorded generally in the high 50,000s psi with muzzle velocities in the mid to high 2600s fps; while chamber pressures recorded in the low to mid 60,000 psi yielded muzzle velocities in the 2700s to low 2800s psi.  We anticipate that the final loads with the MAST Technology cases will yield similar chamber pressures and muzzle velocities.

Future Development of the .408 Cheyenne Tactical  Cartridge: Sniping

            The first 2000 cartridge cases recently arrived from MAST Technology.  As mentioned previously, these cases are not neck sized because the final design is being fine-tuned.  A second order of 10,000 is on tentative order for late summer to early autumn; these will represent the final design.

            Dave Manson offered access to one of his CNC lathes for additional projectile development.  Bronze alloys with multiple lead concentrations are available (Table II).  The

initial load development studies focused on projectiles made from bronze alloy C93200 that contained 7% lead and displayed a Brinell hardness of 72.  C94300 (Special) bronze alloy, which contains 30% lead with Brinell hardness of 30 has been turned into projectiles but as yet, has not been fired.  The projectile with the higher lead concentration has a greater weight.  Future studies will include a review of the bronze alloy C93000 series with different lead contents in order to determine engraving characteristics, weight to muzzle velocity characteristics, characteristics of projectiles in flight and terminal ballistics against hard materials; e.g., light armor, cinder block etc. at various distances up to 2000 meters and beyond.

            During cartridge load development, Dr. Faber was able to make measurements that contrasted chamber pressures as the projectiles, with and without driving bands (full body), translocated through the barrel against the resulting harmonics of the barrel (Figure 9).  Even though his results are preliminary without proper controls, it might be interesting to examine the data (Figure 11). 

In order to obtain direct comparisons between the two types of projectiles, readings were selected where the variable of maximum chamber pressures or amplitudes were similar.  See the top half of the graph.  Both projectiles reach approximately the same maximum chamber pressure or amplitude, while the projectile with the full body reaches this maximum point earlier in time. The driving band projectile builds pressure at a slower rate than does the full body projectile due to the reduced resistance during the early stages of its translocation. This is the reason the driving band projectile requires more powder to produce the same peak pressure as does that of the full body projectile.

The lower curves on the graph represent the output of the strain gauge that Dr. Faber mounted laterally at the bottom of the barrel located near the action. The negative deflection of the curve represents the proportion to the torque on the action due to recoil. The recoil force is proportional to the projectile acceleration, which is proportional to the pressure curve above, minus the bore resistance effect.

The driving band projectile displays an initial jump into the barrel, lands and then decreases its speed during the engraving into the barrel's rifling.  The recoil curve shows the initial movement and the projectile decreases in speed.  Then at the 500-microsecond mark, the projectile becomes fully engraved and breaks free of this resistance resulting in increased acceleration. The pressure curve displays an exponential pressure rise at the beginning and a definite inflection point where the projectile breaks free with the pressure rise becoming more linear. The full body projectile engraves gradually over a greater distance and the initial projectile movement is smoother, without the initial jump effect. The pressure rises to a higher point by the time the engraving is complete, due to the greater engraved length, and pressure rises faster and peaks earlier.

The full body projectile curves were measured with the Christensen graphite-coated barrel, while the driving band projectile curves were measured with the steel barrel.  These differences could undoubtedly influence the vibration curves and more than likely accounts for the reason the graphite barrel curve displays a higher deflection than the steel barrel even though

the pressure curves are of similar amplitude. The lighter more flexible graphite barrel exhibits more deflection for the same impulse. Despite the difference in the two barrels, the curves are quite similar, except for the blip due to the driving band and the fact that the full body projectile's

curve peaks earlier and is shifted earlier in time than the driving band projectile's curve. The bullet exit point is also a bit earlier - around 1900 microseconds.

This preliminary experiment suggests that the initial bore resistance is a significant factor in barrel vibration. The driving function for barrel vibration is the acceleration of the projectile, which is not simply equal to the pressure curve times the bullet base area, but a combination of that force minus the frictional force. There is also a pressure gradient that will reduce the force seen by the projectile's base as it accelerates compared to what the pressure curve at the breech indicates.  This frictional force is most significant during the early stages of projectile translocation and can have a major effect on the pressure rise times, as well as giving rise to blips in the barrel vibration curve as seen in the driving band projectile's case. The barrel vibration frequencies are a direct result of the applied frequencies, that is, the frequency content of the bullet acceleration curve.

Dr. Faber's preliminary results demonstrate that the engraving force can introduce high frequency components to the acceleration curve as seen on the initial part of the driving band projectile vibration curve. High frequency components of significant amplitude would be undesirable, since they would result in greater changes in barrel deflections with small changes in projectile exit times.  Additional experiments are planned with proper controls.

            With the arrival of the new cartridge cases, the first tests will be to shoot for groups out to 2000 meters.  During this period, the ballistic coefficients at various speeds will be determined.  Also during this period, other powders will be examined with the hope of filling the case. Finally, terminal ballistics tests will be conducted against armor at various distances.  Final tests on the

Cartridges are anticipated to be completed by late summer, 2000.  Results will appear as Part III in Tactical Shooter magazine.

            Near the end of the preparation of this article, we joined forces with Warren Jensen (Lost River Ballistic Technologies [LRBT], Arco, ID) to review our design using Prodas 2000 software (Arrow Tech Associates, South Burlington, VT) and if not ideal, to propose a replacement.  Prodas 2000 is an advanced program that creates projectile models, calculates their mass properties, estimates their aerodynamics and stability and simulates test firings.  Warren is a West Point graduate, with a concentration in ordinance engineering and after graduation, spent five years testing, evaluation and use of long range small arms and ammunition.  With LRBT, he currently enjoys major success with 30 caliber designs that are known for extreme accuracy and extended supersonic flights.  LRBT utilizes a proprietary copper nickel-alloy that possesses higher tensile and yield strength along with hardness potential than copper alloys currently being used for solid projectiles.  We feel that this alloy may be ideal for anti-material intervention. Warren will be designing several projectiles for us and for the foreseeable future, we plan to focus on these projectiles rather than the earlier ones.  External and terminal ballistic data will appear as Part III in Tactical Shooter magazine.

            Running parallel with the final stages of cartridge development will be the construction of at least two new prototype rifles that will lead to the manufacturing of production models.  As

mentioned previously, Lloyd DeSantis is designing and will make a semi-auto gas rifle.  Lloyd plans to enlarge his RND 2000 -- currently chambered for the .338 Lapua Magnum cartridge.  I expect a prototype within several weeks for testing.  I suspect if Lloyd is not careful, Pete Forras

will somehow capture the rifle during the testing and a bounty hunter will have to be hired in order to retrieve it.

            The second rifle will be a turn-bolt breakdown modeled after Bill Ritchie's (E.D.M. Arms, Redlands, CA) Windrunner (.50 Browning).  The Windrunner (Figure 11) is an outstanding, rugged rifle that received high marks during a recent USSOCOM testing.  One competitor at these trails was the Barrett M95 turn-bolt action -- the two rifles are very different.  The barrel is hand-removable via an Uzi-style barrel nut.  The electro-discharge machined (EDM) action originates from a billet of aluminum.  A steel insert in placed in the receiver for the engagement of the locking lucks.  The bolt displays an extremely smooth flow.  Because it is a breakdown model, including the barrel, the rifle can be stowed in a hard or soft case smaller in size that what would normally be used for a rifle firing the .50 Browning cartridge.  This rifle yields 0.5 MOA groups at 1000 yards using appropriate cartridges in the hands of trained shooter. 

            Willi and I have joined forces with Bill to downsize his Windrunner by one-third.  We anticipate (hope?) to diet the 34-pound Windrunner down to 19 pounds.  The first step in the plan will be to convert an existing Windrunner to the .408 CheyTac  cartridge.  A barrel the size of a .50 Browning with a .408 CheyTac bore, ordered from Ernie Stallman (Badger Barrels, Inc. Bristol, WI) will be mated to the Windrunner.  A recently manufactured bolt head will accommodate the .408 CheyTac cartridge.  This rifle along with the shop mule, Prometheus will be used for additional cartridge testing as outlined previously.

The second step of the plan will be to construct a prototype de novo.  The dimensions for the Windrunner's receiver will be downsized by one-third in order to create a new EDM program. A new receiver will be made by EDM.  We anticipate the prototype will be finished by this summer -- about the same time as Lloyd's prototype gas gun is completed.

            Assuming the prototype meets our expectations, we have asked EDM Arms to manufacture the first 35 rifles with Christensen's graphite coated barrels for civilian sales -- the first two have already been spoken for including one with a 007 series number from an ex-Special Forces veteran who recently ordered a RND 2000 in the .338 Lapua Magnum caliber for his wife.  Don't mess with this couple!  The receiver will be investment cast finished by EDM.  A name for the model shooting the .408 CheyTac cartridge has been tentatively named Intervention.  Obviously, we believe that there is a potential military market and will explore that market as the little brother to the EDM Arms Windrunner.

            In Europe, Gnter Kirnst tter (AMP Technical Services, Puchheim, Germany) has designed a novel bullpup, turn-bolt takedown in three models: DSR No. 1 (Police), DSR No. 1 (Subsonic) and DSR No. 1 (T. F. [Military]).  Figure 12 illustrates Police model.  Gnter anticipates that he will have a Police model in my hands by this July.  I'm looking forward to testing the second of his rifles -- the first was an Erma SR 100.  I plan an article in Tactical Shooter showing the evolution of one design to the next.  The evolutionary step is major or macroevolution. 

The first 150 rifles of the Police model will be completed by April with 30 going to the German Special Forces.  The Police model will accommodate three different barrels for three

different calibers: .308 Winchester, .300 Winchester Magnum and .338 Lapua Magnum cartridges.  Changeable bolt heads and magazines will be included.  Rifles will be sold in a given caliber, but it would be possible to accommodate all three calibers with one rifle.  The Subsonic model will more than likely be chambered in the 12.7 Anthis cartridge.  G nter would like to chamber the Military version with a caliber larger than the .388 Lapua Magnum cartridge, but smaller than the .50 Browning cartridge.  He is currently taking a very close look at the .408 CheyTac  cartridge.

            An important question deals with the availability of ammunition.  We plan to make available loading dies, cartridge cases and projectiles to reloaders by late summer 2000.  Jeff Hoffman of Black Hills Ammunition has expressed interests in loading cartridges for the commercial market and this is currently being explored.  Some, if not all of the cartridges, will be match.  Other avenues abroad for manufacturing are being explored. 

Future Development of the .408 Cheyenne Tactical  Cartridge: GPMG

Early testing will be conducted with an automatic, magazine-fed .50 Browning converted to the .408 CheyTac caliber.  Many of the tests will be held on the 8000-meter artillery range at Camp Grayling, military reservation located in Grayling, Michigan.  Assuming the .408 CheyTac cartridge withstands the rigors of full automatic testing, a FN MAG 58 or one its clones will be converted to fire the .408 CheyTac cartridge.  We have firm plans to address

conversion of cartridge feeding as well as availability of novel cartridge links.  Results will be addressed as Part IV in Tactical Shooter magazine.

John D. Taylor, Ph.D.

Professor, Wayne State University

Detroit, Michigan 48202

Date: March 13, 2000

Acknowledgments: Willi and I would like to thank Dr. Steve Faber for his continuing assistance while playing a leadership role in our internal ballistics and harmonic studies.  In addition, we want to thank Jim and Jay Bell of MAST Technology who shared their knowledge with us and spent time with us to insure the design of an outstanding cartridge case. We also want to thank Christensen Arms, particularly Dr. Roland Christensen, Evan A. Mitchell and John Mogle for the kindness and help extended to us during our studies.  Special thanks goes to Dave Manson of Dave MANSON Precision Reamers for making his special talents and shop available for our studies.  We are happy to become associated with Bill Ritchie of E.D.M. Arms and look forward to the new breakdown, turnbolt chambered in the .408 CheyTac  that we expect to see during the fall of 2000.  Thanks to Bruce Bertram of Bertram Bullet Ltd. for strengthening the web in his .505 Gibbs cartridge used during the initial phases of the study.  My understanding is that he has strengthened the webs in other turn of the century cartridge cases that he manufactures and sells.  Finally, we want to thank my doctoral student, Carlos Maldonado for the images as well as becoming our main test shooter.

 References

1.       1.      Wyly, M. D.  Combat in the 21st Century.  U. S. News and World Report.  March 16, 1998.

2.       2.      Stevens, R. B. and E. C. Ezell.  1985.  The SPIW -- The Deadliest Weapon that Never Was.  Collectors Edition, Toronto.

3.       3.      Taylor, J. D. 1998. .408 Cheyenne Tactical -- A Novel 2,000-Meter Tactical Cartridge. Part I. Tactical Shooter, Vol. 1, No. 2, pp. 70-74.

4.       4.      Taylor, J. D. 1999. The .338 Lapua Magnum Cartridge: Origin, Development and Future. Part I. Tactical Shooter, Vol. 1, No. 12, pp. 52-66.

5.       5.      Taylor, J. D. 1999. The .338 Lapua Magnum Cartridge: Origin, Development and Future. Part II: The Men Behind the Cartridge. Tactical Shooter, Vol. 2, No. 1, pp. 22-25.

6.       6.      Taylor, J. D. 1997. Parental Cartridge Cases: The Future. Shooter's News, June, pp. 15-27.

7.       7.      Drysdale, W. H. and B. P. Burns.  1988.  Structural Design of Projectiles, In: Gun Propulsion Technology (ed. L. Stiefel), Progress in Astronautics and Aeronautics, Vol. 109, pp. 133-158.

8.       8.      Moss, G. M., Leeming, D. W. and C. L. Farrar.  1995.  Military Ballistics.  Land Warfare: Brassey's New Battlefield Weapons and Technology Series into the 21^st Century.  Vol. 1.  Brassey's, London.

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