[marktwain]

a 3/8” will work for a 9mm (tight, .375 vs .380)

9mm = .355”, .38SPL = .357”

Simply a difference in chamber vs. bore diameter. ;-)

Chamber is about .380, Bore is .355 - .358. Trifling differences for homemade.

I think steel tubing exists in enough quantities, and is easily modified in inside diameter, to offer a variety of sources for .22 barrel liner material. It is not even that hard to make rifling, though it would take much more time than printing the gun.

Lots of tubing out there that could be made to work.

http://www.microgroup.com/Products/StockTubing/fractional_tubing.asp

[ArrogantBustard]

Chamber is about .380, Bore is .355 - .358. Trifling differences for homemade.

See #15.

.025 is a lot of windage; much of your propellant is going to blow by the bullet not doing any good, unless you use a fairly soft lead hollow base bullet.

Headspace is another issue. 9mm headspaces on the case mouth, so you need a real chamber for it. .38SPL headspaces on the rim; a much better choice for an improvised weapon.