Great responses - thanks. In order:

1 Flint: I used open sights. I have a light scope from the era but it is impossible to avoid scope creep due to recoil.

I believe Webley's hand-crafted rifling took some time to produce (90 minutes?). Seeking to cut costs again, they eventually saved labour by progressing to button-rifling, albeit at a capital cost in terms of machinery. Button rifling improves accuracy (compared with hand-cut rifling), as a check online will confirm (I posted a link in a post or replying to a post some weeks ago).

One has to be careful to replicate one's hold to produce good groups with these rifles, due to recoil nuances.

2 Rancidtom: Yes, you make valid points. I checked the crowns visually and, to the best of my ability, the inside of the barrels but only via torch light - which is probably insufficient.

The loading taps all seemed firm and aligned but - of course - one could not tell they were original. I also performed the lever test - opening the tap and de-cocking, to ensure the air held.

3 Bill57: Yes, one has to bear these points in mind. I really do not know if the taps are/were 100% aligned. I am saying that accuracy improved as a result of button rifling and, being machine produced, there must also have been greater consistency. By the way, are you certain it is your tap that is responsible for poorish accuracy?