Evidence indicates that the use of helmets by Sikhs in the army of the Sikh Kingdom of Maharaja Ranjit Singh seems to have been primarily confined to the cavalry.
In the early years of the Sikh Kingdom, the cavalry seems to have worn turbans and we do not find any accounts of troops of the Empire wearing a helmet until the 1831 meeting at Ropar between Maharaja Ranjit Singh and the British Governor-General of India, Lord William Bentinck in 1831.
Earlier images of Sikh cavalry as well as earlier accounts mention the wearing of turbans rather than helmets. Doctor Murray a British physician wrote the following in a letter dated January 1, 1827 to Captain Wade, the British resident at Ludhiana:
‘…while the Raja was at breakfast, two regiments of Cavalry (about 1000 men in all) had arrived and taken up ground about two hundred yards in front. They were drawn up in line and after performing a few evolutions which were done very slowly, they marched round in review by threes. The men were dressed in red jackets and Pantaloons. They had also red lined pagries.’ 
The gradual use of helmets among the cavalry may have been part of the major reorganization of the cavalry under Maharaja Ranjit Singh’s European officers which first started in 1822 with the appointments of French Generals Allard and Ventura.
The cavalry of the Lahore Empire was composed of three main groups:
An early account from 1838 provides a general overview of the Sikh cavalry at that time as well as makes observations regarding the type of head-dress commonly worn among the various branches:
The Cavalry is Runjeet's favourite arm, and he has spared no pains to render it efficient. The total strength is estimated at 40,000, or thereabouts of which 4,000 only are regulars. They comprise two regiments of Lancers and six of Dragoons; disciplined according to the French system by Monsieur Allard, a distinguished officer of the Imperial Army. The regular Cavalry are well mounted and equipped, and in large bodies work well together. The Dragoons are fine men, armed with long carbines, pistols and swords. Their appointments are of black leather, with jack boots. Clothing scarlet, with green facings, and close fitting steel helmets, of the Roman pattern. The Lancers are dressed in blue, with scarlet facings, and a profusion of lace; have high cloth caps, and are armed with lances twelve feet in length, surmounted with the tri-coloured flag. The Ghorechurras or body-guard, 2,000 in number are the best mounted of the Sikh Cavalry. To them Ghorechurras or body-guard, 2,000 in number are the best mounted of the Sikh Cavalry. To them is entrusted the safety of the Rajah's person. They are excellent swordsmen, and equally expert with the matchlock and lance. Their dress is superb, being an under tunic of padded crimson silk, over which is worn ornamental chain armour of the most beautiful workmanship, covering almost every vulnerable part. The head-dress, a conical turban of bright yellow silk, surmounted by a brazen head piece, from which the chain armour descends, and is crowned by long waving heron plumes. 
The cavalry of the Sikh Empire in general lacked standardization in terms of their equipment and uniform. The irregular cavalry composed of the Ghorchurra Fauj and the Jagirdari Fauj presented the highest degrees of variation in uniform including the diverse use or turbans or helmets. This lack of standardization can primarily be attributed to two factors. Firstly they were required to purchase their own uniforms and weapons. Secondly a rivalry existed as each strived to outshine each other in terms of their uniform and equipment.
The irregular troops consist chiefly of cavalry, who are obliged to furnish their own horses, weapons, and clothing; some are armed with spears, shields, and bows, and the greater part of them have matchlock guns; they are excellent soldiers, brave and vigilant, and are quickly rallied after a defeat. (Orlich, 1845) 
The irregulars, in their dress and appointments, fully justify the appellation which their habits and mode of making war obtained for them. Cotton, silk, or broad cloth tunics of various colours, with the addition of shawls, cloaks, breast-plates, or coats of mail, with turbans or helmets, ad libitium, impart to them a motley but picturesque appearance. (Steinbach, 1845) 
The irregular levies and jagirdari contingents of horse, not included in the above, cannot be accurately determined, but they may be fairly estimated at 30,000 men. These were the picturesque element in the Maharaja's reviews. Many of the men were well-to-do country gentlemen, the sons, relations, or clansmen of the chiefs who placed them in the field and maintained them there, and whose personal credit was concerned in their splended appearance. There was no uniformity in their dress. Some wore a shirt of mail, with a helmet inlaid with gold and a kalgi or heron's plume; others were gay with the many coloured splendours of velvet and silk, with pink or yellow muslin turbans, and gold embroidered belts carrying their sword and powder horn. All wore at the back, the small round shield of tough buffalo hide. These magnificent horsemen were armed some with bows and arrows, but the majority with matchlocks, and which they made excellent practice. (Griffin, 1892) 
Even among the troops of the regular cavalry, we also find inconsistencies in uniform, weapons and armour including the mixed use of turbans and helmets.
Almost every one of the Sikh officers of these regular troops was dressed according to his own taste; some in English, others in French uniform, or in a mixture of both; some wore turbans, or caps with shawls wrapped round them, and others helmets and chakos: some had high boots with coloured tops, other shoes; some wore white, and others coloured pantaloons. (Orlich, 1845) 
In a set of four paintings done be a native painter of Sikh horsemen, three of the horsemen are depicted wearing Indo-Persian style helmets. Although identified by the Victoria & Albert Museum as dating from 1840 to 1845, given their drawing style they may be older and possibly from the 1820’s to the 1830’s. These are very important because two of the three horsemen in the paintings wearing helmets are lancers. Although there are many eyewitness accounts of dragoons of the regular cavalry wearing helmets, these two painting represent conclusive evidence that lancers also wore helmets as well.
An important drawing that appeared in the memoirs of Doctor John Martin Honigberger (Thirty-Five Years in the East, publ. 1852) depicts a cavalry officer wearing a helmet. The image in the book is captioned as ‘Charaina Sowar (a Cuirassier), Plate V’ and depicts a Sikh soldier on horseback wearing an Indo-Persian style helmet and body plate armour. Although the armour has been incorrectly identified as being of the char-aina variety which is composed of four segmented plates, the horseman is in fact wearing a one-piece French cuirass body armour. Cuirassiers typically wore the cuirass body armour with a helmet. These cuirass’s were a gift of the French King Louis Philippe and 500 of them were brought to Punjab by Maharaja Ranjit Singh’s French General Allard.
Letter dated Dec 3, 1836 from Lord Auckland (Governor-General of India) to Sir Charles Metcalfe: ‘You will have seen in the papers the arrival of General Allard in a French frigate. He brings a present of 500 cuirasses and 2000 stands of arms from the French king to Ranjit Singh, and is accredited French Charge d’ Affaires at Lahore’ 
The use of a helmet with the cuirass body armour in the regular cavalry under General Allard’s command was observed by William Barr who visited the Lahore Kingdom in 1839:
On their right were two regiments of Allard's cuirassiers, the most noble-looking troops on parade. The men and horses were all picked, and amongst the former are to be seen many stalwart fellows, who appear to advantage under their cuirasses and steel casques (helmets). Particular attention seems to have been paid in setting the men well up, and their accoutrements are kept in the highest order. Many of the officers wear brass cuirasses, and their commandant is perhaps the finest man of the whole body, and looked extremely well in front of his superb regiment (Barr, 1844) 
Barr also provides a detailed written description of a Cuirassier wearing a helmet which is almost identical to the drawing of a helmeted Cuirassier in Dr. Honigberger’s memoirs:
The uniform consisted of a short blue coat and a pair of dark trousers with a narrow red stripe tightly strapped over Wellington boots and spurs. The cuirass was of highly polished steel, or brass, and bore a Gallic cock in the centre of the breast plate. The head-dress was a round steel cap from the apex of which sprung a red horse hair plume. From the cap depended a curtain of chain mail, which hung down over the neck and shoulders. The arms consisted of a flint-lock carbine, and a long steel sword depending from the waist-belt by steel chains. A leather waist-belt, and a pouch belt completed the very effective outfit. 
Details of General Allard’s Dragoons cavalry regiment and their use of helmets can be found in the Turban Helmet section.
1. Devinder Kumar Verma, Foreigners at the Court of Maharaja Ranjit Singh, (Patiala: Arun Publications, 2006), 20
2. "Runjeet Singh's Army", Parbury's Oriental Herald and Colonial Intelligencer, Volume II, July to December, 1838, 575
3. Leopold von Orlich, H. Evans Lloyd Translator,Travels in India, Volume 1 (London: 1845), 229
4. Lieut.-Colonel Steinbach, The Punjaub; being a Brief Account of the Country of the Sikhs (London: 1845), 59
5. Sir Lepel Griffin, Rulers of India, Ranjit Singh (Oxford: 1892), 143
6. Leopold von Orlich, 229
7. Jean-Marie Lafont , Fauj-i-Khas, Maharaja Ranjit Singh and his French Officers (Amritsar: Guru Nanak Dev University, 2002), 101
8. William Barr, Journal of a March from Delhi to Peshawur (London: 1844), 245-246
9. C. Grey, H. L. O. Garrett, European Adventures of Northern India 1785 to 1849 (New Delhi: Asian Educational Services, 1993), 22