And as far as I can figure the first element to see action was the Welland Canal Field Battery fighting as infantry at Fort Erie on 2 June 1866 during the Fenian invasion of the Niagara Peninsula. It's been onward and upward since then.
Happy 305th Birthday to the Royal Artillery, formed 26 May 1716
"Ubique means that warnin’ grunt the perished linesman knows,
When o’er ’is strung an’ sufferin’ front the shrapnel sprays ’is foes;
An’ as their firin’ dies away the ’usky whisper runs
From lips that ’ave n’t drunk all day: “The Guns! Thank Gawd, the Guns!”