Does anyone have one of these?  It's been awhile now, but I remember slugging bore 3 times with very soft lead from muzzle end.  Now heres the problem..I can't remember if I drove slug thru to breech..but I suspect I did..as I always do.  But my measurements (Starrett .0001" micrometer) always came up .250" groove to groove.  Now this has ratchet shaped rifling..First thought maybe bore is choked?  But I a loose fitting slug going thru to breech would have raised a red flag.  Books say .255 groove?  Maybe that ratchet rifling..like Henry rifling is throwing me off.  I do know a .257 dia. bullet seated in case and making slight engraving with rifling origin fits without any problems. What do you experts think?

Tim,
If I were you I would try and obtain an original round and take it apart, that would probably give you the best dimensions. These rounds were only made by Eley and Kynock as far as I am aware.Bill Fleming in his book on British Sporting Rifle Cartridges gives the bullet dia., as 0.255". If your using a lead bullet with BP it will 'bump up'. I haven't come across reloading tools of the period for this calibre and other than Shotgun cartridges, Long Range Rifle ammo and Big 'Bore' Calibre Rifle ammo for Africa and India, the small calibre rounds never seem to have been reloaded by the sportsmen of the period. The ammo was fairly weak and not really suitable much beyond 100 yards. Jeffrey like several 'London Names' didn't make rifles himself, they were sourced from outside his company and sold under his name, his business was purely a retail outlet. Just like The Army and Navy Stores, and, E.M. Reilly and Co., to name just two. Fleming gives case dimensions, if you need them, just shout.
Harry

In my guns with what I presume you mean by "ratchet rifling", ie., ramp rifling, I never get "book" values but a few thou inches less. Have always dismissed this to there being very little of groove-to-groove that is full width.

I have always associated ramp rifling with European paper patch military cartridges. The high end of ramp rifling looks like it would do a great job of cutting paper patches into strips.

Grisen

Thats good to know Joel,   I have plenty to chose from in that size.  I did find my notes, only got to the range with this one  once few years back..I was using the little Lyman 252435 @51grs.  I started out with very light TrailBoss charges.  Lowest charge shot close to p.o.a. @ 50yds..but anything heaver shot higher..6" or more.  Next time I think I will try H4227 and a heaver .257 dia. bullet.  I gotta cut back on work hours...way too much time between outings!