Okay im revamping my Wum-1, which is in need of serious help.  Without getting into all the details I am trying to track down the piece that the gas tube "block" slide into inthe middle portion of the barrel that also has the bayonet lug and hole support hole for the cleaning rod.  My Wum had the bottom portion of it cut off and does not support the bayonet nor cleaning rod.  name and any links of places that sale, or if anyone has a Romy kit barrell they aren't using.

Gas block

That is what I thought, but when I searched on sites with parts their pics only shows the gas tube.  that is why I was confused and submitted this post.

So on removal and replacement, I'm guessing that all is needed is to knock out the pins and slide off (with a little help)