Need help Identifing a British Bulldog revolvers make and caliber

That is what I originally thought also, but I slugged out the barrel and it measures exactly .400! Bullets for a .442cf are supposed to be .434-.436, trying to squeeze a .434-436 bullet down that .400 barrel sure seems like a disaster waiting to happen, even .427-,430 44 caliber bullets seem dangerous. I understand that the revolver looks like a 442cf/44 webley but the barrel slugging out to .400 just seems to small to shoot .427-.436 bullets through without causing a lot shaving of the bullet as it enters the barrel and excessive dangerous pressures. I know these revolvers were made with sloppier tolerances than modern day guns but that sure seems like an awfully big difference in cylinder to barrel bore size in this revolver, what is weird is that a 44 Russian or 44 American case fit very well in the revolver cylinders but both of those calibers also shoot .427-.430 bullets. That is why I am wondering if there was some odd bottle necked caliber that was made back then that was similar, but shorter than a 38/40 or 44/40? where it starts out as a 44 caliber at the base but then necks down to a 40 caliber at the mouth of the case. I have actually made such cases from some starline 44 special brass cut down to proper length and then necked down to shoot .401 diameter lead cast bullets, I use an 80% trail boss powder load and Federal 150 LPP and i am getting 2"-3" groups at 7 yards. The cases come out easily and the primers appear normal so I can at least shoot the old roscoe. I know you are supposed to use BP in these old guns but trail boss is specifically designed for such applications and as long as soft lead bullets are used, supposed to be safe in black powder framed revolvers. I was just hoping that I could get an actual name on what this odd caliber actually is called.

Being i know nothing about these i thought i would do a little research. Never knew so many different British bulldogs were made. The closes references i could find to a .400 bore was a .380 rook which used a .375 bullet. I couldn't find anything on actual bore diameters or any info on the type of bullet used. I know some older BP guns used a hollow base bullet that would expand at the base when fired to fit a larger bore(like a minieball). Still .025 still seems like a lot of expanding but maybe the bore is worn too? The case would probably be smaller than your cylinders though being you aid a .44 will fit diameter wise but i also seen several references of people fining out the chambers were bored on these old guns with no reference of changing the bore's, maybe they were started by gunsmiths and never finished or these just squeezed a larger bullet down the bore, made custom ammo or who knows. Hope this helps rather than confuses you more. At any rate i'm doubting you'll be able to shoot this with such odd dimensions.