Returning at the end of nine months, he was again ordered on field service to quell an insurrection in the neighbourhood of Saugor, and was thanked in the despatch of the officer commanding the artillery for his conduct in action with the insurgents at Jhirna Ghaut on 12 November 1842.

Having passed as interpreter in the native languages, Olpherts was given the command of the 16th Bengal Light Field Battery, and joined Sir Hugh Gough's expedition against Gwalior.

Crossing the Black Sea, he rode over the Zigana mountains in the deep snow; but soon after reaching Kars he was detached to command a Turkish force of 7000 men to guard against a possible advance of the Russians from Erivan by the Araxes river.

As a result, the Battery he commanded (now part of the Royal Regiment of Artillery) was later awarded his name as their title, commemorating both William Olphert and the distinguished actions of the unit that day.

His citation for the action reads: For highly distinguished conduct on the 25th of September, 1857 when the troops penetrated into the city of Lucknow, in having charged on horseback, with Her Majesty's 90th Regiment, when gallantly headed by Colonel Campbell, it captured two guns in the face of a heavy fire of grape, and having afterwards returned, under a severe fire of musketry, to bring up limbers and horses to carry off the captured ordnance, which he accomplished.Olpherts almost surpassed this piece of bravery by another two days later.

However, Olpherts, with Colonel Robert (afterwards Lord) Napier, sallied out with a small party, and by his cool determination brought in the wounded of the rearguard as well as the guns.

At the close of the campaign Olpherts received the brevets of major and lieutenant-colonel, as well as the Victoria Cross, the Indian Mutiny medal with two clasps, and the companionship of the Bath.

In 1859–60 Olpherts served as a volunteer under Brigadier (Sir) Neville Chamberlain in an expedition against the Waziris on the north-west frontier of the Punjab, thus completing twenty years of continuous active service.

From 1861 to 1868 he commanded the artillery in the frontier stations of Peshawur or Rawal Pindi, and in that year he returned home on furlough, when he was presented with a sword of honour by the city and county of Armagh.