Some people have apparently started printing out Slug’s YEHW that he released a few weeks ago.
So if you ever wanted to print your own cylinderless hammer shot (plunger tube cycles around instead of the barrels), the files are here:
https://www.thingiverse.com/thing:4798771>The hardware kit is $12 to $15 depending on barrel length. It takes 300 grams of filament to print. Assembly is only slightly more difficult than a HYPR. 