Just when you thought it was safe to get back on the forum…(Cue “Jaws” music)
Unless anyone spots any glaring errors or omissions, this is my final draft.
I hope someone (anyone!) learnt something from it. I know I did writing it. If you want to learn more about a particular round/projectile/subject, write a mini-article on it, you learn a lot.
[quote]This Mini article started out purely about the M-22 Frangible bullet, but unfortunately I found it impossible to write this without giving the reason for its development. As such it has turned into an article on the birth of WWII air to air gunnery training.
Practice makes perfect, right? Pilots fly countless circuits, marksmen fire countless rounds, and I’m sure Michael Schumacher has probably lost count of how many countless millions of kilometre’s he has driven in training. So it stands to reason the best way to train aerial gunners is letting them actually shoot at real planes. But using ball ammunition against aircraft could would be dangerous, possibly probably definitely fatal at some point and a waste of resources. So, how do you shoot at a real aircraft with real guns without causing damage to the target aircraft? Posing this question led to one of the US Army Air Forces’ most unusual training programs in World War II, often referred to as Operation Pinball.
In June 1941 the first gunnery school for the training of the aerial gunners who would man the turrets and guns of the bombers of the USAAF was established at Las Vegas, Nevada. Over the next two and a half years, aerial gunnery schools were also opened in Arizona at Kingman and Yuma, Texas at Harlingen and Laredo, and in Florida at Tyndall Field near Panama City and an instructors’ school at Buckingham Field, near Ft. Myers.
At all the schools, the training aids were primitive, consisting of makeshift devices as shotguns mounted on the back of trucks (known as E-5’s) or the more sophisticated gun camera and projection screen trainers, such as the Jam Handy and Waller trainers. The most realistic training came from using gun cameras mounted in actual gun positions of bombers, but it still took time to develop the film and correction to technique could not be given in flight. Theoretically a gunner could go a whole flight without a single round hitting the target aircraft. The man responsible for the gunnery training aids used at Harlingen in 1942 was Major Cameron Fairchild, and he is credited with the idea of developing a bullet that could be fired at a real fighter without actually shooting it down.
To research ways to make a frangible bullet, Fairchild enlisted the help of two professors from Duke University, Paul Gross and Marcus Hobbs. In autumn 1942, Fairchild presented his idea to the National Defense Research Committee (NDRC) where the proposal immediately hit an obstacle, the Army’s Ordnance Department, responsible for development of all weapons and ammunition. They argued that any bullet that was truly frangible would not have the same ballistics as live ball or tracer ammunition and would not fire from normal machine guns. They also worried that if such a bullet were fired at a target aircraft, the plane and its pilot would need special armour and other protection. The results were that the NDRC allowed research to continue but with limited funding and low priority.
The idea was for a .30 calibre round that would simulate the trajectory of the .50 BMG used in bomber aircraft. The weapon used was the T-9 Machine gun. Unfortunately I am having trouble locating any information on it. There were several ideas’s put forward for the projectile but the most successful were glass, ceramics, and lead/Bakelite mixtures. As a result these were the ideas that were concentrated on.
The Bakelite Corporation supplied projectiles and sheets of lead/Bakelite mixture (so projectiles could be hand turned); Ceramics were supplied by the Homer-Laughlin Company and the Ceramics Department of Rutgers University. Corning Glass Works supplied two types of glass projectiles, annealed and processed.
To test these materials, cylindrical projectiles, .310” in diameter and .875” in length, were created and fired through a smoothbore gun with a bore diameter of .313”. The results showed that the ceramic, Bakelite/lead and processed glass projectiles were superior to the annealed glass. The ceramic was no better than the Bakelite/lead and was harder to manufacture, thus leaving two possible projectile materials, processed glass and Bakelite/lead.
The processed glass projectiles were specialled heat treated to induce an effect known as “Prince Rupert’s Drop”. My understanding of this effect is that a small amount of molten glass is dropped into water forming a tear drop shape. The exterior is rapidly cooled while allowing the interior to slowly cool and shrink, creating tension. The bulbous end could be subject to all manner of abuse while the pointed end was extremely delicate and would cause the projectile to disintegrate if even slightly damaged. Sounds perfect for a frangible bullet, and it would probably be fine if fired through a bolt action such as the 1903 Springfield or even a semi auto like the M-1 Garand but the rigors of being fired through a fully automatic machine gun were too much for it, leaving only the Bakelite/Lead. Several Bakelite/Lead compositions were supplied, with three standing out, RD-42-79, RD-42-90, and RD-42-93 (the last set of digits referred to the relative size of the lead particles, Bigger number=Smaller particles). Due to density only the -93 was suitable. The next decision was the projectile shape. After testing the best shape was found to be the same as the standard ball round.
Thus the T44 was born.
Initially called the T44, it was adopted as the M22. There is a round with a different powder was called the T-74. The mottled grey-green projectile is composed of 50% powdered lead bonded with 50% Bakelite by volume. The T-44/M-22 normally has a green over white bullet tip, but can sometimes appear with either no tip colour or just a white tip. These are simply rounds that have escaped the complete painting process. The T-74 has a tan over green bullet tip. There is also a T44E1 which was an Ordnance Department contract to Remington for a frangible bullet similar to Remington’s commercial bullet “Spatterless”, made of lead and sodium carbonate. Testing started in 1944 and the project was cancelled because the bullets broke up upon firing. Further test were made with a zinc type bullet (also broke up) and a M2 bullet jacket filled with lead/zinc dust (too much penetration). The T44E1 project was cancelled in 1945.
One unusual frangible round has a short sharp bullet with a black tip (and a hemispherical base) and was actually for testing the armour plate on the target aircraft.
There is an extremely rare and often faked Frangible Tracer, identified by a red and white bullet tip. According to Chris Punnett’s article on The Development of the Frangible Projectile the only mention of these in the Duke and Princeton reports is the possibility of using tracers to act as a rocket to help match the trajectory of the .50 BMG.
Funnily enough, in correspondence with Chris I have learnt that when he visited Duke University in the early 1990’s and enquired about the T-44 project, they vehemently denied any involvement in war-time projects and claimed they had no records of any such a project.
My records show the M22/T44 has a charge of 11gr of SR4759 (T74 uses SR4900) with a 108gr Bakelite (RD-42-93) Projectile which is lighter than the M2 AP (55 gr WC 852 or IMR 4895 with 165.7gr AP Proj), M1 tracer (50 gr IMR 4895 with 143.5gr Tracer Proj) or M25 tracer (50 gr WC 852 or IMR 4895 with 145.7gr Tracer Proj). Due to the light powder charge the velocity was about 1324fps at the muzzle. The M1 Tracer was doing about 2665fps. As the M22 generated app. 420ft.lbs compared to the M1’s 2263ft.lbs. My guess would be as they needed a low energy round they chose to use a slow moving light projectile which would loose energy quickly. (According to Page 47 of TM 9-1305-200 (Small Arms Ammunition) of 1961 the max range was approx. 1900ft) The requirements for penetration state that the M-22 “shall not perforate aluminium plate at 25 yards” The plate is specified as “3/16 in. Dural 2024 T4 with Brinell Hardness of 105 to 125 under 500 kilogram load.” The accuracy figure in TM 9-1305-200 states 2” at 100 yards which is about 1.9 Minutes of Angle