In 1804 Shrapnel shell was employed in the attack on Surinam, and favourably reported on. Its after progress, although frequently retarded by defects of manufacture, the imperfection of the fuse, and the difficulties incidental to all considerable novelties in artillery, was nevertheless steady and triumphant. This destructive shell, which in every country goes by the name of the inventor, is in more extended use and is more highly thought of, if possible, in the present day than ever. The testimony that Shrapnel received to the value of his shell was ample. The Duke of Wellington wrote to Sir John Sinclair on 13 Oct. 1808 to testify to the great benefit which the army lately under his command had derived from the use of Shrapnel's case-shot in two actions with the enemy; he considered it most desirable that the use of the invention should not be made public, and, as therefore Shrapnel would be deprived of the fame and honour which he might otherwise have enjoyed, he should be amply rewarded ‘for his ingenuity and the science which he has proved he possesses by the great perfection to which he has brought this invention.’ In the following year Wellington wrote to Shrapnel on 16 June from Abrantes, to tell him that his shell had had the best effect in producing the defeat of the enemy at Vimiera on 21 Aug. 1808. Sir William Robe [q. v.], who commanded the artillery in the Peninsula, wrote to Shrapnel from Torres Vedras on the same date that the artillery had been ‘complimented both by the French and all our own general officers, in a way highly flattering to us. … It [the shell] is admirable to the whole army and its effects dreadful. … I told Sir Arthur Wellesley I meant to write to you. His answer was: “You may say anything you please; you cannot say too much.”’ Admiral Sir Sydney Smith in 1813 was so enthusiastic about these shells that he begged Shrapnel, in case the board of ordnance would not send him enough of them, to let him know how he might get them at his private expense, and soon after he ordered a supply of two hundred privately from Carron. Sir George Wood, who commanded the brigade of artillery at Waterloo, wrote to Shrapnel from Waterloo village, on 21 June 1815, that had it not been for his shells it was very doubtful whether any effort of the British could have recovered the farmhouse of La Haye Sainte, ‘and hence on this simple circumstance hinges entirely the turn of the battle.’ This was the general testimony to the value of the invention, and at a later date commanders in the field, such as Lord Keane, Sir William Nott, Sir Robert Sale, Sir George Pollock, Lord Gough, Sir Harry Smith, and others, wrote after Shrapnel's death to his son, expressing the very high estimation in which they held these shells.
Shrapnel was promoted to be colonel in the army on 4 June 1813 and regimental colonel on 20 Dec. 1814. On 10 Sept. 1813 he addressed the board of ordnance on the subject of some reward being made to him, and pointed out that for twenty-eight years he had been unremitting in his exertions to bring his invention to the great excellence and repute it had attained, and that it had cost him several thousand pounds from his private purse. The board's reply was simply that they had ‘no funds at their disposal for the reward of merit.’ In 1814, however, the treasury granted him a pension of 1,200l. a year for life for his services, in addition to any other pay to which he was entitled in the ordinary course. The government undoubtedly meant to act justly, but, unfortunately, the niggardly interpretation of the terms of the grant by the public departments charged with the scrutiny of expenditure construed it in such a way that Shrapnel would have been better off if it had never been made. Thus the grant was interpreted to include all his improvements in artillery besides the shell; further, in consequence of Shrapnel being already provided for by this special pension, he was passed over in promotion to the commandantship of a battalion.
Shrapnel was promoted to be major-general on 12 Aug. 1819, and retired from active employment on 29 July 1825. He became a colonel-commandant of the royal artillery on 6 March 1827, and was promoted to be lieutenant-general on 10 Jan. 1837. A short time after this promotion Shrapnel was the guest of William IV at Brighton, when the king personally acknowledged his high sense of Shrapnel's services, and signified a desire to bestow upon him some honour. Shrapnel would appear to have intimated a desire for some honour which would descend to his son, as Sir Herbert Taylor wrote to him from Windsor Castle on 23 April 1837 expressing the king's readiness to confer a baronetcy upon the inventor; but William died soon after, and nothing further was done. Shrapnel died at his residence, Peartree House, Southampton, on 13 March 1842, a disappointed man; he was buried in the family vault in the chancel of Bradford church, Wiltshire.
In addition to the invention of shells, Shrapnel compiled range tables, invented the brass tangent slide, improved the construction of mortars and howitzers by the introduction of parabolic chambers; he also constructed a duplex disappearing mounting for two pieces
