British 13Pdr. Shrapnel Shell, WWI

British 13Pdr. Field Gun
The Ordnance QF 13Pdr. is a British Horse Artillery weapon developed in 1904. Light and mobile, horse artillery was intended to be quickly deployed on the battlefield at relatively close range, usually in a cavalry support role.
The QF 13Pdr. (Quick Fire 13 Pounder) could send a 12.5 lb shrapnel shell out to a range of 5900 yards. It was used up to the early years of the "Great War", when its short range became a problem and it was withdrawn from service.

Quick Fire guns were originally a naval development. Using fixed ammunition (cartridge and shell as one unit) rates of fire could be much higher than earlier guns. On ships, with guns mounted securely to the deck, this worked well. In the field, using wheel mounted carriages, the recoil would displace the gun which then had to be reset and aimed with every shot. This nullified the rapid fire advantages of modern breech-loading technology.
The French were first to solve this problem in 1897 with a system which allowed the gun barrel to slide on a rail and transfer the recoil energy into an oil-filled piston, which then used that stored energy to push the barrel back into position. This allowed the gun carriage to remain stationary, allowing a much faster rate of fire. This design concept was universally adopted for field guns.

13pdr Fixed Round

British 13Pdr. Fixed Shrapnel Round
The 3 inch diameter shell body is stamped on the side: "Q.F. 13Pdr.II FS K 5.2.07" (The fired projectile is repainted)
The brass case is marked as follows:" 13 Pdr.I 11/10 V.S.M. 1910 C.F." It has a brass primer No.1 MK II.
The brass fuze is a combination Time and Percussion type calibrated from 0 to 22 seconds.

Time Fuze Components

Sectioned Round Diagram
This Shrapnel Shell design is credited to Colonel Boxer of the Woolwich Arsenal and became the standard form. The iron body had a cavity at the base containing a small charge of gunpowder; above this is a "pusher plate" with a central tube leading to the fuze. Musket balls are packed around that tube in a resin matrix. The top is closed by a mounting ring with a time fuze. When the fuze fired, preferably just above and in front of the enemy, the base charge expelled the balls which continued towards the target.  

A variation of this, known as the Universal Shell, was developed by Krupp of Germany. The inert resin matrix was replaced by TNT. It would behave the same in flight, but it would also function as an HE shell on impact.

Shrapnel was gradually superseded by the High-Explosive shell but continued to be used into the early years of WWII.

British No.80 Time & Percussion Fuze
This is a combustion time fuze, which works by the controlled burn of internal delay trains of compressed black powder.
The brass body consists of an automatic fuze igniter under the nose cap, two crescent shaped delay trains, and a percussion (impact) detonator located at bottom center. The only adjustable component is a rotating index ring (above the numbers) which can be set at the safe ("+") setting or any delay time from 0 to 22 seconds.
At right is a sectional diagram. When the shell is fired, inertia forces the fuze igniter down onto the firing pin, setting it off. This creats a flash in the upper chamber which is directed to the top delay ring via a "lead in" port.

The top delay ring burns in a counter clockwise direction. If the lower delay ring is set on safe "+" the lead-ins are blocked and that top ring will burn to the end with no where to go. When the lower ring is set at "0" seconds the lead-ins are aligned and the flash from the igniter will be conducted directly to the ignition element at the base, exploding the shell. The zero setting will create the effect of close range canister shot, by bursting the shell as it leaves the muzzle.
The diagrams at upper right and lower left show the internal configuration for "0" seconds.

The illustration below right shows the fuze configuration set at "5" seconds. The top ring starts burning as described, moving left-to-right (yellow). After a short distance it reaches the lead-in to the second ring. Once there it ignites the second delay below and that starts burning right-to-left, traveling a short distance before reaching the lower lead-in and exploding the shell.
As the setting ring is advanced the distances between lead-ins are increased, adding to the delay time.

British RHA Crew