.303 British "RL 1938 B IV" incendiary


D.Dietz’ notes say that it is a rare incendiary. How rare?


Vlad, unfortunately this is not what I would call a “rare” round. Here in the UK you can buy these for about £3 each, or about $4.75. I have seen them cheaper as well. Do you have any .303 rifles? If you have more of them try shooting one somewhere that allows tracer. They are filled with White Phosphorous which is forced out of a hole in the side of the bullet in flight and will produce a spiral smoke trail.


I have a strong feeling that either TonyE or DocAV will jump all over me when I post this because they are right most of the time and I am not.
I believe this is an anti aircraft round. I will say no more than that to reduce my subsequent humiliation.


No Vince, it was used for anti-aircraft fire, but it was principally an air service store. As Falcon says, it left a smoke trail due to the phosphorus being spun out of the weep hole and igniting on contact with the air. For this reason it was often referred to (particularly by Kynoch) as a smoke tracer.

It came into service in 1928, although the prototypes had first been made in 1918. The WWI Buckingham Mark I was the round nosed incendiary, the B.II was the spitzer version and the B.III was the flat nosed type which was designed to punch a better hole in balloon fabric.

The next stage was an experimental incendiary (which evolved into the B.IV) with a step in the bullet jacket designed to cut a larger hole in the balloon fabric so allowing more hydrogen to be dragged out behind the bullet and ignited by the phosphorus.

The B.IV stayed in service for most of WW2, the last examples being made at RL Woolwich in 1943. However, it had largely been replaced at that date by the B Mark VII which was a particularly effective incendiary.

Have a look at this YouTube footage. The first few seconds show B.IV rounds being fired and leaving their distinctive smoke trail.




Just helping TonyE
Tony, what is “air service store”?


An “air service store” means that it was usually issued and used by the RAF.


Here’s a sectioned projectile. The large part in the center is the lead plug. It has 3 deep grooves that run the length of the plug. These grooves allow the phosphorus to have contact with the air so as to burn and produce the smoke trail. There is a fusible plug in the jacket (in this picture it is on the bottom portion of jacket just above the case neck and below the lead plug). Note also the copper cup which sits between the lead plug and lead base. The copper cup defines the annular air space and I suspect prevents the lead from melting and clogging the vent hole in the jacket.