Totally agree that the pipe guns look ridiculous, but in the fallout universe I doubt there would be much production of new guns (especially new designs). I would guess the majority of guns would have been produced before the apocalypse and would only be modified if they became broken. I see the pipe guns as more viable than finding a modified or enhanced PPSh41 or even more outlandish the laser guns.
I guess there wouldn't be many Mark Serbu clones running around. lol
Haha probably not and if there are, how easy would it be to find machining equipment and produce 3+phase power to run lathes/mills and source high quality steel.
The fallout universe is littered with workbenches and materials, and everything is powered from fusion. Finding a talented machinist would be a problem, but not impossible. The Fallout series for me breeds thought experiments. Either that or need a new hobby.