Plastic pipe than fits snugly inside other pipe?

[Gerrydelasel]

I want to make a short of pneumatic spud gun / pop gun thing, so I'd like to find a plastic pipe that will fit snugly inside another pipe to create a piston. I'm not very knowledgeable about what sorts of pipe are available (and suppliers websites never give exact internal and external dimensions). Can anyone think of two common British sorts of pipe that would do this, with the least need for O-ring seals and the like? I'm thinking a finished muzzle diameter of one to two inches would be fine.

 

[footprints]

Tried a bit of flowplast 32mm (1¼") solvent weld inside some pollypipe push fit pipe 40mm (½") that was a snug fit.
Not 2" but that's one option.
Waste pipes come in 32mm and 40mm but in the wonderful world of plumbing solvent weld and push fit or compression pipes are not all the same bore / OD!

 

[freddiemercurystwin]

Why not go for a cannon? UK instructions ...... http://baddadgreatkid.blogspot.com/2011/03/how-to-build-your-own-potato-cannon.html