On the recomendation of CC/dt, I was able to get on inter-library loan
Purdey Gun & Rifle Makers, The Definitive History by Donald Dallas. This work is a comprehensive history of the company, the family,and the men that made the guns, as much as the guns themselves, and there was very little discussion of the barrels, and no mention of any specific named pattern nor, after the mid-1820s, if any barrels were out-sourced. I was able to establish the progression of barrels used from the excellent pictures.
In summary: prior to the 1840s all brls were twist. In the 1840s-1860s Laminated steel and large scroll asymmtric 2- and 3- Iron Damascus appear
About 1870, a distinctly finer small scroll symmetric 3- and 4- iron pattern appears, very similar to the 'Finest' damascus used on D grade Parkers
c. 1890, most of the brls were Whitworth steel
Here are the details:
p.15
Purdey began producing his own barrels in the mid-1820s.
Prior to that time, most were obtained from Charles Lancaster (‘CL’ marked) or William Fullerd (‘WF’ marked)
p. 27
Barrels made by Purdey were stamped ‘JP’ after 1826
Also Thomas Evans ‘TE’ and Thomas Parkin ‘TP’ in mid-1820s.
No further mention of any out-sourced barrels thereafter.
1818 – 16b Flintlock #14 - twist
1821 – 14b Dbl percussion shotgun #287 – twist
1844 – 16b Dbl percussion rifle #3845 - Laminated
1863 – 12b Dbl Bastin/Purdey slide action pinfire #6424 – Damascus ?2 rod
1864 – First pattern thumb-hole pin-fire #6829 - ?Laminated Damascus
1866 – 12b Dbl First pattern thumb-hole #7225 – Laminated steel
1867 – 40 cal. Dbl Express rifle #7464 – Large scroll 2 Iron Damascus
1868 – 12b Second pattern thumb-hole #7745 – Large scroll 3 Iron Damascus
1869 – 12b muzzle-loading shotgun #7902 – Large scroll 3 Iron Damascus
1872 – 10b bar-in-wood hammer gun #8623 – First appearance of Fine small scroll annular 4 Iron Damascus
1873 – 12b bar-in-wood hammer guns pair #8998&9000 – same Damascus.
c. late 1870s – Introduction of Quality A – E
Jan. 1, 1880 - Pair #10614/10615 were delivered to Mr Hunt by James Purdey 'The Younger' with The "New Whitworth Fluid Pressed Steel".
1881 – Bar-in-wood hammer gun #11090 – same Damascus.
1885 Catalog - Quality A- Best Gun “The barrels of best Guns can if desired be made of Sir Joseph Whitworth & Co.s fluid pressed steel at an extra cost...
Quality B- “fine Damascus barrels.” No other mention of barrel material.
Crolle pattern illustrated is same small scroll, symmetric, annular, 4 Iron.
1884 – Beesley gun #11837 – same scroll pattern but 3 Iron
1886 – 8b hammer rifle #12371 – same scroll pattern but 3 Iron
c. 1890s – Guns illustrated had Whitworth steel.
Sure wish we knew if Purdey made that "Finest" Damascus after about 1870. The book states that Aston Snr. began with Purdey's in the 1850s, and his son, Harry, was also a barrel maker until 1930.
