If there’s that much change in bore size from breech to muzzle, then it’s possibly a tapered bore for firing single projectiles, not just birdshot. Dual purpose shotguns were popular among 19th century British sportsmen because of the variety of wild game in Africa and India. The last six inches or so of the bore are where the round balls were stabilized and accurized. “Shot and ball” loads are usually engraved onto the barrels, action, or stamped into the water table.
Muzzlecap, I stand corrected. The book is Game Rifles and Guns, by Richard Akehurst. It's a fine book, goes until details about the coming of choke to barrels, how the Greener family were at odds about it, but does not devote a chapter to the WR guns.
) pieced out gun orders, and some big name firms had their guns made by entirely by someone else like WC Scott. The script on the barrels could be from a passing style fad, or from the unique engraving style of the individual barrel jobber house or gun maker. A common shotgun could easily have been ordered by WR from one of the many other manufacturers there. 
The British put gain twist in many of their bp rifles and a taper bore in almost all guns. Unbelievable gunmaking skill
If the muzzles are smaller than the breech diameter, then your gun is for shot and ball unless explicitly stated in engraving on the gun itself. It probably shoots 600 grain round balls accurately out to 75 yards
Could also be the reason the original owner ordered it with the cheekpiece and rifle style trigger guard.
Correct. I thought my prior comments addressed this. A mind is a terrible thing to lose…
When you find someone with a bore gauge, see if they also can measure the barrel wall thickness of each barrel, starting at the breech and measuring every 4-5” down to the muzzles. Doesn’t take long and will either save you problems or give you peace of mind. There’s a basic acceptable shotgun barrel wall thickness that of course I cannot now recall because my memory is like Swiss cheese, but it’s somewhere around 0.20” and the breeches like 0.30”
I once had a curiously short barreled percussion gun It had a pronounced internal tapering a long choke in effect I concluded going on its general style & use of old parts that it was got up by some gunmaker for his own use as a Covert gun for Snipe perhaps. It had a Side plug conversion evidently from new not ex flint which for English guns is seldom met with other than the conversion's .
Yes, I will measure barrel wall thickness as well.
A sentiment and commitment to history many many people share with you. Here on this particular forum I think we are supposed to say “any historic firearm” and thereby bypass the non muzzleloader types. You are too well liked for anyone to want to see you get in hot water
Westley ,from the configuration of the gun shewn here,Definately out sourced guns.This is fun. Feltwad is on to something. Some owner of the weapon in the past 170 years could have had the muzzles opened up for a cylinder choke effect. Guns this old have often been subjected to a lot of tinkering. It’s rare to find one in original condition.
My own experience with the Westley Richards ledgers is they are/ were not necessarily well maintained. The same gun could have come in for repairs, but the guy presently handling the ledgers won’t go looking for subsequent entries of the same serial number. Sometimes you have to get enough information in hand to point him in a new direction so he can narrow down his search for other ledger entries.
Question: Is there any writing on the gun that you can see about loads, drams, “not for ball” etc? A great many shotguns were made for both shot and ball, and the wider choke / muzzles could be a result of that function one way or another.
Last, WR is a Birmingham firm, and 170 years ago Birmingham was the center of English firearms production. You could get any gun made there, because there were makers for every bit and piece of guns. Even firms of WR’s caliber (
You have a fine weapon here in hand! Having the barrel thicknesses checked should alleviate any safety concern. Hope you use it.
