Not a firearm, but it uses BP :-)

[John Taylor]

These type wood splitters were just hammered into the end grain. Some of the wood would go up into the bore and acted as a projectile. The projectile ( wood plug), when fired, was driven into the log causing it to split.

[Mr_Sheesh]

I've seen people split logs with just a bored hole, tamped with sand; Down side is that if the log has voids inside, the pressure all leaks out and not much splitting happens.

[Keith]

I still have this old one. Last used when I was a kid back in the 50,s.
The grounds of the Presbyterian church in Alexandra, Central Otago NZ had this huge Pine tree that was cut down. To split the trunk up they used this. I was sent up to Walls Garage to fetch some Blasting Powder. Some fuse was put in the hole in the side The powder poured in till nearly full, stoppered with newspaper then pounded into the centre of the trunk. They used a Maul rather than a sledge so the end is not so damaged. A corn sack was hung on the end and the fuse lit. We all stood clear.
Well it split that old trunk into about 6 long pieces all went flying and the bag and gun were tossed about 20 yds away.
What fun that was for a kid. My old man got a bit of a fright and never used it again.
I think its only good for soft wood as the Aussie hardwoods where I live now would be too dense to drive it in. Such as the block its on.
IMG_2277 by [url=https://www.flickr.com/photos/141809689@N05/]