The pattern 42 rifle started out as a percussion musket, newly built to replace the flintlocks which had been converted to percussion locks that were destroyed in the fire at the Tower of London in 1841. In 1852 (according to British Military Firearms 1650-1850, by Howard Blackmore), while the Pattern 51 rifle was being issued, it was decided to upgrade the P42 musket to a rifle, designated as the Altered Pattern 42, for use by Marines. This constituted boring out the 0.753 in barrel to 0.758 and adding three to four rifling grooves. The Sea Service musket (for Naval use) was approved in the same year for upgrade (becoming the Altered Sea Service rifle) and was rifled to the same calibre and ultimately used the same projectile.
P42/Sea Service bullet introduction
P42/Sea Service rifled musket trial bullet
1st pattern P42/Sea Service rifled musket
