Here's a quote from Brig. Gen. James Edmonds "Military Operations France And Belgium"

Despite improvisation and inexperience, in 1916 British war industry produced 33,507 machine-guns, 5,192 trench mortars with 6,500,000 rounds, 127,000 long tons (129,000,000 kg) of explosives and 84,000 long tons (85,000,000 kg) of propellants. Mills bomb production rose to 1,400,000 per week and the output of shells rose from 4,336,800 in the first quarter of 1916 to 20,888,400 in the final quarter, for an annual total of more than fifty million 148,000 long tons (150,000,000 kg) of ammunition were expended on the Somme from 24 June – 23 July and 101,771 long tons (103,404,000 kg) were landed in France.

SO FAR SO GOOD

Heavy guns and howitzers burst on firing, due to defective shells made from inferior steel, which had hairline cracks, through which the propellant discharge detonated the shell. 8-inch howitzer fuzes failed so often, that the battlefield was littered with duds and an attempted remedy made the fuzes fall out. Many shells failed to explode, due to deterioration of the explosive filling; defective fuzes in all heavy guns caused premature detonations, while many guns misfired due to poor quality barrels. 60-pounder guns averaged a premature every 500 shrapnel rounds and 4.5-inch howitzer shells exploded in the barrel or 4–5 yards (3.7–4.6 m) beyond the muzzle, the crews becoming known as "suicide clubs". Some propellants were not fully consumed on firing, requiring the barrel to be cleaned after each shot, which slowed the rate of fire. Some copper driving bands on 18-pounder field gun shells were too hard, which reduced the accuracy of the gun; when H.E. ammunition was introduced late in 1915, premature detonations and bulges occurred, with a burst barrel every thousand shots. There was a shortage of buffer springs, replacements were sometimes worse than worn ones and spare parts for every mechanical device in the army were lacking. Some shells exuded explosive in the summer heat, flare fillings decomposed, phosphorus bombs went off spontaneously, the firing mechanism of the heavy trench mortars failed on 1 July, Stokes mortar ammunition was chronically unreliable until replaced by improved designs, many Mills bombs went off early, rifle grenades were either premature detonations or duds and a make of rifle cartridge jammed after firing and had to be scrapped.

NO TO CLEVER BY THE SOUND OF IT

Sounds like Dud ammo to me. And this from someone who attained the rank of Brigadier General.