Hello and Webley Senior problem.

[Rev al]

Many thanks to all the above, chaps.
Most appreciated. I can confirm the gun was not put away cocked. The barrel is unobstructed. Leather barrel seal IS in place but dry (I oiled it).
I’ll check and oil as suggested above.
Many thanks
Al

[abellringer]

Hi ex W & S head service dept. technician for 10 years; I'd guess with the gun being stored for so long, the barrel has crushed the leather breech seal; this means there's no ''friction'' there to hold the barrel in place. Maybe a little oil on the breech seal will rejuvenate it, but don't put the barrel into the breech block, you need to allow the washer to expand. Alternatively fit a 'rubber' seal and this will help a lot. Some lube in the cylinder with a good quality medium oil or if you want to spend a little; Abbey gun lube which has a graphite content would help a lot, but the gun isn't that powerful, so don't flood it, you'll just end up squirting stuff out of the barrel. Ref the barrel stirrup, just check it moves freely and the plunger is moving to operate it.