Grenade, Hand, No. 75, Anti tank (Hawkins)

                 The No. 75 grenade was in fact a small anti tank mine or anti vehicle mine.  The was not enough explosive in an individual mine to cause serious damage to a tank, or more correctly the heavier tanks produced later in WWII but would seriously damage or destroy wheeled vehicles.  The Mk. I was introduced for service in June 1942 but was likely in service prior to that.  It was declared obsolete in March 1946.  The Mk. II was introduced in June 1943 and declared obsolete in July 1955.  The Mk. III history is slightly more interesting, not officially introduced during the war it was declared obsolete in December 1945, then reintroduced for service in March 1949 and extended to Naval Service in November 1953.  It was again declared obsolete in July 1955.                 

Grenade, Hand, No. 75 Anti-tank Mk. I

This grenade was officially adopted for British service in June 1942.  It was adopted for use by American Airborne troops in the drops on Normandy in 1944 and perhaps after.  It is commonly known as the “Hawkins Grenade”.

 The body is a 1 pint capacity flat tin with a short neck and screw cap at one end.  The igniter holder is made of tinplate and formed to make two igniter pockets.  The holder is then soldered to the centre of the body.  Slots are cut into the holders on the upper side and tabs at the end of the pockets that are bent in to retain the igniters in position.  Support brackets are soldered onto either end of the body.  The striker plate attaches to the support brackets by tabs.  The striker plate has a transverse groove formed in the centre that projects out the bottom and forms the striker.  The striker groove is positioned directly above the slots in the igniter holder.  The body is filled with Nobels Explosive No. 704B plus four exploders, Burrowite plus four exploders, or a combination of 1/3 Burrowite and 2/3 Nobels.  The exploders are cylindrical pellets 7/8 inch diameter and three inches long of Polar Dynamite and are placed in the body at the lower end directly under where the detonators would be.

 The igniter assembly consists of an “Igniter, No. 75 Grenade Mk. II” and a No. 27 detonator.  The igniter operates by chemical reaction.  It consists of a tinplate tube closed at one end by flattening the tube.  A circumferential groove is formed on the inside of the tube about half way down.  A lead washer is pressed into the groove inside the tube.  The hole in the washer is filled with a composition of potassium chlorate, sugar and charcoal.  A small glass vial containing a mixture of 93% sulphuric acid and 7% nitric acid is contained above the washer in the closed end of the tube.  Cotton wool packing protects the vial.  A thin rubber sleeve is rolled onto he open end of the igniter to provide a means of attaching the detonator.

 The grenade is painted buff.  The manufacturers mark, date of manufacture and designation are embossed into the side of the grenade opposite the striker plate.   Filling details are stencilled onto the bottom of the grenade.

 For use the igniter must be prepared by inserting the detonator, open end first, in the open end of the igniter until it rests on the lead washer.  The rubber sleeve is then rolled down to hold the detonator in place.  The igniter is then placed in one of the igniter pockets of the grenade detonator first.  The tab on the igniter pocket is then bent in to hold it in positon.  The operations are then repeated for the other igniter pocket.  When properly done the glass vial portion of the igniter is directly under the slots in the igniter pockets.  The grenade can then be placed as a mine or thrown in the path of a vehicle.  When the grenade is run over, the striker plate bends and  forces the striker groove down onto the igniter assemblies.  When the glass vials are crushed the acid comes into contact with the composition in the lead washer.  A chemical reaction occurs and a flash produced that initiates the detonator and causes the grenade to explode.


Ike with Paratrooper, D Day

                 Grenade, Hand, No. 75 Anti tank, Mk. II

This is an improvement on the Mk. I to correct some of the defects of the original grenade.  The body is the same as the Mk. I and in fact may have the Mk. I designation embossed on the body.  The igniter holder has been modified to have two inclined pockets to give more reliable initiation by placing the two detonators close together so that the detonation of one will cause the detonation of the second.  The tabs at the end of the igniter pockets have holes to take a soft wire wire pin which hold the detonators in place.  The body is strenghtened directly under the head of the detonators by having a saddle piece soldered on.  The central bridge of the saddle piece lies between the open ends of the igniter pockets and prevents sideways movement of the detonators.  The striker plate has been strengthened by using stronger support brackets and having a longitudinal corregation projecting out from the body.  The tabs on either side of the support brackets are designed to take a length of signal cable or strong cord so that several grenades could be strung together to form a necklace.

The filling is as for the Mk. I.  The exploders used with the Mk. II are Polar Dynamite containing 25% Nitroglycerine.

The detonator No. 83 Mk. I is of the percussion type overcoming the problems experienced with the chemical crush type used in the Mk. I.  The body is of molded plastic with two holes drilled in it.  One hole, drilled completely through end to end takes a glass capsule filled with an igniferous detonator composition.  The other hole, drilled from the top to meet the other hole, takes a steel pin that acts as a striker.  The glass capsule is sealed in position by a sealing compound.  The steel striker pin is also sealed in position.  The other end of the body has a spigot to take a No. 27 detonator that is cemented in place.

The body is painted brown with two red X's painted either side of the filling cap.  The filling details are stencilled in the same manner as the Mk. I.
                 Grenade, Hand, No. 75, AT, Mk. III

The body of the Mk. III is different from earlier models in that it does not have the filling cap on the end.  The body is a one pint capacity tinned plate tin.  A saddle piece is soldered on the upper side of the body to provide reinforcement under the detonators.  Two detonator holders are soldered on top of the saddle piece angled slightly outwards.  Two striker plate brackets are soldered near the ends of the body.  The striker plate is made of steel and is attached to the brackets by tabs on the brackets fitting through holes in the plate and being turned over.  A steel securing pin fits through end tabs on the detonator holders to keep the detonators in place.  A piece of tarred whipcord attaches the pin to the grenade.

The detonator is the No. 83 Mk. II.  It is constructed in the same manner as the Mk. I but uses the detonator No. 98 Mk. I rather than a No. 27 detonator.

The grenade is filled with 2 C.E. Pellets separated by a felt disc, located at the bottom of the body where the detonators would lay.  The remainder of the body is filled with 1 lb. 8 oz. 15 drams of poured TNT.  After filling, a waxed felt closing pad is placed over the explosive and the lid put on and closed by a folded seam and approved dope to seal the body against moisture.

The grenade is painted buff with three red X's stencilled on the lid.  The bottom side, opposite the striker plate has all other markings.  There is a green band with TNT in black marked on it.