Can anyone solve this problem?

[Graemevw]

Yes, so it seems the Japanese had invented the mobile phone by 1930.

The one that's come up for sale also doesn't appear to be made of solid gold as the advert promises 🙁

[ccdjg]

If the barrel is used as a plunger to cock an internal spring and piston, then is it possible the barrel can also be pulled forward a little to reveal a direct loading port?
The pin behind the trigger pin indicates the main sear is to rear in which case the piston must latch a fair way back when cocked. Since the barrel protrusion is relatively short and the outer spring will become coil bound once about 3/4 of the barrel has been pushed in, there is a fair amount of space inside the action unaccounted for. There should be easily enough room for an internal length of barrel which has been milled down to its centre line or similar to enable loading if pulled forward.

Matt, I can see what you mean about the unaccounted space in the action and the possibility of a section of concealed barrel with a loading access port which can be pulled out for loading. However, what I can't see is, once the barrel has been loaded and pushed back, why doesn't it fly forward again under air pressure when the gun is fired, so exposing the port and losing all pressure? I presume you would need some sort of latch to temporarily hold the barrel back during the firing cycle?

[DrGunn]

Matt, I can see what you mean about the unaccounted space in the action and the possibility of a section of concealed barrel with a loading access port which can be pulled out for loading. However, what I can't see is, once the barrel has been loaded and pushed back, why doesn't it fly forward again under air pressure when the gun is fired, so exposing the port and losing all pressure? I presume you would need some sort of latch to temporarily hold the barrel back during the firing cycle?

I had wondered about a barrel latch and it probably wouldn’t be difficult to achieve enough holding force with a spring detent or similar to overcome the force on the barrel - it just has to put up more resistance than the projectile. How was the barrel held in on other direct loading guns such as the Pope air pistols?
Although I'm sure a pull out barrel could be made to work work, I think your removable inner barrel solution would be much simpler to implement.